Together, respiration and photosynthesis keep the levels of carbon dioxide and oxygen in the atmosphere _____.

A. fairly constant

B. always changing

C. decreasing

D. increasing

Answer:

There ain't enough info in the question to answer but, I can say that reactants were there before the reaction, but products were produced by the reaction.

Explanation:

I don't really know how to answer this.

Answer:

Wegener discovered that the Appalachian Mountains of the eastern United States, for instance, were geologically related to the Caledonian Mountains of Scotland. Pangaea existed about 240 million years ago. By about 200 million years ago, this supercontinent began breaking up

Answer:

What evidence did Wegner use to develop his hypothesis? = Alfred Wegener suggested that continental drift occurred as continents cut through the ocean floor, in the same way as this icebreaker plows through sea ice. Wegener put his idea and his evidence together in his book The Origin of Continents and Oceans, first published in 1915.

Continental drift describes one of the earliest ways geologists thought continents moved over time. Today, the theory of continental drift has been replaced by the science of plate tectonics.  

The theory of continental drift is most associated with the scientist Alfred Wegener. In the early 20th century, Wegener published a paper explaining his theory that the continental landmasses were “drifting” across the Earth, sometimes plowing through oceans and into each other. He called this movement continental drift.  

Pangaea

Wegener was convinced that all of Earth’s continents were once part of an enormous, single landmass called Pangaea.  

Wegener, trained as an astronomer, used biology, botany, and geology describe Pangaea and continental drift. For example, fossils of the ancient reptile mesosaurus are only found in southern Africa and South America. Mesosaurus, a freshwater reptile only one meter (3.3 feet) long, could not have swum the Atlantic Ocean. The presence of mesosaurus suggests a single habitat with many lakes and rivers.

Wegener also studied plant fossils from the frigid Arctic archipelago of Svalbard, Norway. These plants were not the hardy specimens adapted to survive in the Arctic climate. These fossils were of tropical plants, which are adapted to a much warmer, more humid environment. The presence of these fossils suggests Svalbard once had a tropical climate.

Finally, Wegener studied the stratigraphy of different rocks and mountain ranges. The east coast of South America and the west coast of Africa seem to fit together like pieces of a jigsaw puzzle, and Wegener discovered their rock layers “fit” just as clearly. South America and Africa were not the only continents with similar geology. Wegener discovered that the Appalachian Mountains of the eastern United States, for instance, were geologically related to the Caledonian Mountains of Scotland.  

Pangaea existed about 240 million years ago. By about 200 million years ago, this supercontinent began breaking up. Over millions of years, Pangaea separated into pieces that moved away from one another. These pieces slowly assumed their positions as the continent we recognize today.

Today, scientists think that several supercontinents like Pangaea have formed and broken up over the course of the Earth’s lifespan. These include Pannotia, which formed about 600 million years ago, and Rodinia, which existed more than a billion years ago.

Tectonic Activity

Scientists did not accept Wegener’s theory of continental drift. One of the elements lacking in the theory was the mechanism for how it works—why did the continents drift and what patterns did they follow? Wegener suggested that perhaps the rotation of the Earth caused the continents to shift towards and apart from each other. (It doesn't.)

Today, we know that the continents rest on massive slabs of rock called tectonic plates. The plates are always moving and interacting in a process called plate tectonics.  

The continents are still moving today. Some of the most dynamic sites of tectonic activity are seafloor spreading zones and giant rift valleys.  

In the process of seafloor spreading, molten rock rises from within the Earth and adds new seafloor (oceanic crust) to the edges of the old. Seafloor spreading is most dynamic along giant underwater mountain ranges known as mid-ocean ridges. As the seafloor grows wider, the continents on opposite sides of the ridge move away from each other. The North American and Eurasian tectonic plates, for example, are separated by the Mid-Atlantic Ridge. The two continents are moving away from each other at the rate of about 2.5 centimeters (1 inch) per year.  

Rift valleys are sites where a continental landmass is ripping itself apart. Africa, for example, will eventually split along the Great Rift Valley system. What is now a single continent will emerge as two—one on the African plate and the other on the smaller Somali plate. The new Somali continent will be mostly oceanic, with the Horn of Africa and Madagascar its largest landmasses.

The processes of seafloor spreading, rift valley formation, and subduction (where heavier tectonic plates sink beneath lighter ones) were not well-established until the 1960s. These processes were the main geologic forces behind what Wegener recognized as continental drift.

Answer:

Oxygen, bromine, iron, helium

Explanation:

[tex]\Delta H^o_f[/tex] is defined as the standard enthalpy of formation. By definition, the standard enthalpy of formation is equal to 0 kJ/mol for the substances in their standard states, that is, at room temperature and 1 atm pressure.

Simply speaking, looking at the substances given, we need to understand whether their states agree with what we expect to see at standard conditions (e. g., sodium is a metal, fluorine is a gas, bromine is a liquid at standard conditions). Those are substances consisting of just one type of atoms.

Answer: D is the right option

Explanation: if the speed of the molecules are randomly fast that they are only restricted by the wall of the container, it therefore means that the matter is in gaseous state. If the speed are fast to an extent that they transfer heat to another thereby making them fast to move about, the matter is in liquid state. But when the molecules only vibrate about a fixed point, the matter is in solid state

The correct answer is D. It determines what state the matter is in.

The particular state in which matter is is dependent on the sped of the molecules hat compose matter.

Matter is composed of small particles called molecules. These molecules are in constant motion and bump into each other frequently.

In solids, the molecules that compose matter only vibrate or rotate about a fixed position.

In liquids, the molecules that compose matter can move about at low speed.

Molecules of a gas move at high speed. We can see that the particular state of matter is defined by the speed of the molecules that compose it.

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Second row of periodic table can have maximum of eight electrons which are occupied within s and p block section by occupying 2 and 6 electrons respectively and thus becoming stable thus it doesn't have d block section.

Periodic table is a tabular arrangement of elements in the form of a table. In the periodic table, elements are arranged according to the modern periodic law which states that the properties of elements are a periodic function of their atomic numbers.

It is called as periodic because properties repeat after regular intervals of atomic numbers . It is a tabular arrangement consisting of seven horizontal rows called periods and eighteen vertical columns called groups.

Elements present in the same group have same number of valence electrons and hence have similar properties while elements present in the same period show gradual variation in properties due to addition of one electron for each successive element in a period.

Learn more about periodic table,here:

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Answer:

Most common insulation materials work by slowing conductive heat flow and--to a lesser extent--convective heat flow. Radiant barriers and reflective insulation systems work by reducing radiant heat gain. To be effective, the reflective surface must face an air space.

Explanation:

To be effective, the reflective surface must face an air space.

Answer:

Acids when dissolved in water produce hydrogen ions.

Explanation:

Answer:

Sexual reproduction can be described as the method of reproduction in which the offsprings produced will have half the chromosomes as compared to the parent cell. The other half of the chromosomes to make a complete set would arise from the other parent. In this way, the offspring produced will carry half of the chromosomes from the female parent and half from the male parent.

Crossing over and independent assortment are two phenomenons of meiosis due to which genetic diversity occurs and the offsprings born are not exactly similar to the parent cell.

Answer:  The four cells that are produced by meiosis has only one of each chromosome. One of these four cells from one parent combines with another from the other parent to produce the offspring. An offspring gets half its chromosomes from each parent. But the exact combination of chromosomes it gets from each parent is random. So, each offspring ends up with a unique set of genes different from its parents and other offspring.

Answer: 900.33moles

Explanation:Please see attachment for explanation

Answer:

There are 899.88 moles.

Explanation:

To solve this problem we'll need to use Avogadro's number, which tells us that in one mole of a species, there are 6.023x10²³ atoms (or molecules).

With the above information in mind we can calculate the moles in 5.42x10²⁶ atoms of calcium:

Answer:

b) 1,1,2

Explanation:

                   2 - Cl - 2

                   6 - O - 6

                   2 - H - 2

by semireactions, the chloride ion (Cl) is balanced with HClO3 and the oxygen is balanced with water:

Cl2O5 + H2O → 2 HClO3

Answer:

Electrons are always marked negative Hence electronic energy is also always taken as negative. It is because when an electron is at infinite distance from nucleus , there the kinetic energy of that electron can not be calculated. So, it is taken to be zero . ... And thus the energy of electron becomes less negative

Answer:

A: 2.525 x 10⁻⁴ mol

B: 2.583 x 10⁻⁴ mol

Explanation:

Part A:

Data Given:

Convert Temperature to Kelvin

T = °C + 273

T = 21.3 + 273 = 294.3 K

Convert mL to liter

1000 mL = 1 L

5.1 ml = 5.1/1000 = 0.0051 L

Solution

no. of moles can be calculated by using ideal gas formula

                         PV = nRT

Rearrange the equation for no. of moles

                          n= PV / RT . . . . . . . . . (1)

where

P = pressure

V = Volume

T= Temperature

n = Number of moles

R = ideal gas constant

where

R = 0.08206 L.atm / mol. K

Now put the value in formula (1) to calculate no. of moles of

              n = 1.2 atm x 0.0051 L / 0.08206 L.atm.mol⁻¹. K⁻¹ x 294.3 K

              n = 0.0061 atm.L / 24.162 L.atm.mol⁻¹

              n = 2.525 x 10⁻⁴ mol

no. of moles of gas (H₂O) = 2.525 x 10⁻⁴ mol

_______________

Part B:

Data Given:

Convert Temperature to Kelvin

T = °C + 273

T = 21.3 + 273 = 294.3 K

Convert mL to liter

1000 mL = 1 L

5.2 ml = 5.2/1000 = 0.0052 L

Solution

no. of moles can be calculated by using ideal gas formula

                         PV = nRT

Rearrange the equation for no. of moles

                         n= PV / RT . . . . . . . . . (1)

where

P = pressure

V = Volume

T= Temperature

n = Number of moles

R = ideal gas constant

where

R = 0.08206 L.atm / mol. K

Now put the value in formula (1) to calculate no. of moles of

              n = 1.2 atm x 0.0052 L / 0.08206 L.atm.mol⁻¹. K⁻¹ x 294.3 K

              n = 0.0062 atm.L / 24.162 L.atm.mol⁻¹

              n = 2.583 x 10⁻⁴ mol

no. of moles of gas (H₂) = 2.583 x 10⁻⁴ mol

Answer:

The correct answer is A) circulatory

Explanation:

The circulatory system collects metabolic wastes from the blood, which will be eliminated by the kidneys through urine.

The kidneys are responsible for the elimination of waste, acids and excess fluid from the body, maintaining the balance of water, salts and minerals. Blood flows into the kidney through the renal artery.

Answer: a. 0.05mol/dm3

bi. 0.045mol/dm3

bii. 4.41g/dm3

c. 84.8%

Explanation:Please see attachment for explanation

Directly determining the number of moles of KNO3 formed from KI is not feasible without a specific chemical reaction pathway, as KI typically does not directly convert into KNO3.

To determine the number of moles of KNO3 created when 0.03 moles of KI is completely consumed, we need a balanced chemical equation for the reaction involving KI and how it transforms into KNO3. Unfortunately, without a specific chemical reaction indicating how KNO3 is formed from KI, accurately calculating the moles of KNO3 produced directly from KI is challenging since KI typically does not transform directly into KNO3 through a simple chemical reaction. In typical laboratory or industrial settings, KNO3 is formed through different chemical pathways that do not directly involve KI as a reactant.

To determine the moles of KNO3 created from 0.03 moles of KI consumed,

Write and balance the chemical equation representing the reaction between KI and KNO3.

Use stoichiometry to calculate the moles of KNO3 formed from the moles of KI consumed.

Apply the coefficients of the balanced equation to convert moles of KI to moles of KNO3.

Therefore, without the explicit chemical reaction provided, we can conclude that the direct transformation from KI to KNO3, leading to a calculation of moles of KNO3 produced from a given amount of KI, is not standardly feasible. For accurate calculations, the exact chemical equation is necessary.

Answer:

233.856 L

Explanation:

The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C are used and are reference values for gases. And in these conditions 1 mole of any gas occupies an approximate volume of 22.4 liters.

So first of all you should know the amount of moles that represents 835 g of SO₃. For that, you know that:

So: SO₃= 32 g/mol + 3*16 g/mol= 80 g/mol

Now a rule of three applies as follows: if 80 g of SO₃ are contained in 1 mol, 835 g of the compound, how many moles are there?

[tex]moles=\frac{835 g* 1 mole}{80 g}[/tex]

moles= 10.44

Finally, you apply a new rule of three as follows: if, according to STP, 1 mole occupies a volume of 22.4 L, 10.44 moles, how much volume does it occupy?

volume=[tex]\frac{10.44 moles*22.4 L}{1 mole}[/tex]

volume=233.856 L

The volume of 835 g SO₃ at STP is 233.856 L

To find the volume of 835 g of SO₃ at STP, determine the number of moles and then use the molar volume for gases at STP. The calculation yields approximately 234 liters, the mass, in grams, of a molecule of aspirin (C₉H₈O₄) as 2.99 × 10⁻²² g and   the number of atoms in 5.78 mol NH₄NO₃ as 3.13 × 10²⁵ atoms.

a)The volume, in liters, of 835 g SO₃ at STP can be found by using the molar volume concept. At standard temperature and pressure (STP), one mole of any gas occupies 22.4 liters. Here’s the step-by-step solution:

The molar mass of SO₃ is calculated as follows:

S (Sulfur): 32.07 g/mol

O₃ (Oxygen): 3 × 16.00 g/mol = 48.00 g/mol

Total molar mass of SO₃ = 32.07 + 48.00 = 80.07 g/mol

Number of moles of SO₃ = Mass / Molar mass = 835 g / 80.07 g/mol ≈ 10.43 mol

Molar volume at STP = 22.4 L/mol

Volume of SO₃ = Number of moles × Molar volume = 10.43 mol × 22.4 L/mol ≈ 233.63 L

b. Mass of a molecule of aspirin (C₉H₈O₄):

First, find the molar mass of aspirin:

Molar mass of C₉H₈O₄ = 9 × 12.01 (C) + 8 × 1.01 (H) + 4 × 16.00 (O)

Molar mass ≈ 180.17 g/mol

Next, use Avogadro's number (6.022 × 10²³ molecules/mol) to find the mass of one molecule:

Mass of one molecule = molar mass / Avogadro's number

                = 180.17 g/mol / (6.022 × 10²³ molecules/mol)

                 ≈ 2.99 × 10⁻²² g

c. Number of atoms in 5.78 mol NH₄NO₃

First, determine the number of molecules in 5.78 mol:

Number of molecules = 5.78 mol × 6.022 × 10²³ molecules/mol

                                  ≈ 3.48 × 10²⁴ molecules

Next, determine the total number of atoms in one molecule of

NH₄NO₃: 1 N + 4 H + 1 N + 3 O = 9 atoms

So, the total number of atoms is:

Total atoms = 3.48 × 10²⁴ molecules × 9 atoms/molecule

                   ≈ 3.13 × 10²⁵ atoms

Therefore, the volume of 835 g SO₃ at STP is approximately 234 liters, the mass, in grams, of a molecule of aspirin (C₉H₈O₄) is 2.99 × 10⁻²² g and   the number of atoms in 5.78 mol NH₄NO₃ is 3.13 × 10²⁵ atoms.

Complete question.

Find each of the following quantities:

a. the volume, in liters, of 835 g SO₃ at STP

b. the mass, in grams, of a molecule of aspirin (C₉H₈O₄)

c. the number of atoms in 5.78 mol NH₄NO₃

Answer: 3.295moles

Explanation:Please see attachment for explanation

Zn    +  Cu²⁺   →    Zn²⁺ +  Cu

Explanation:

The overall equation of this redox reaction is combination of the two half equations. The similar species on both sides are cancelled out leaving a net overall reaction:

           Zn → Zn²⁺  +  2e⁻      oxidation step

           Cu²⁺ + 2e⁻ → Cu        reduction step

Combining both equations:

Zn + Cu²⁺ + 2e⁻  → Zn²⁺  +  2e⁻  + Cu

since the common specie on both sides is  2e⁻, they cancel out to give an overall reaction:

                      Zn    +  Cu²⁺   →    Zn²⁺ +  Cu

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Final answer:

The overall equation for the displacement reaction where zinc replaces copper is Zn(s) + Cu2+ (aq) → Zn2+ (aq) + Cu(s).

Explanation:

The question concerns the determination of the overall chemical reaction for a displacement reaction where zinc displaces copper from its solution. Starting from the half-reactions, the oxidation half-reaction is Zn(s) → Zn2+(aq) + 2e-, which indicates zinc is being oxidized by losing electrons. The reduction half-reaction for copper is Cu2+(aq) + 2e- → Cu(s), showing that copper ions are being reduced by gaining electrons. When we combine these two half-reactions, we must ensure that the electrons lost by zinc equal the electrons gained by copper to balance the reaction. Thus, the overall reaction is Zn(s) + Cu2+ (aq) → Zn2+ (aq) + Cu(s). This equation represents a single displacement reaction where zinc metal is transformed into its ionic form and copper ions are deposited as copper metal.

Answer:

Hellium

Explanation:

Data Given:

Krypton

Helium

Xenon

Neon

doesn't have true Octet =?

Solution:

Octet Rule:

The atoms have 8 electrons in their valence shell and have stable electronic configuration.

Now we will look for the electronic configuration of each given noble gas to look for octet rule

1. Krypton (Kr)

Atomic No. 36

Electrons per shell: 2, 8, 18, 8

Electronic configuration: [Ar] 3d¹⁰, 4s², 4p⁶

So

it have 8 electrons in its outer (valance) shell and obey octet rule

___________________

2. Hellium (He)

Atomic No. 2

Electrons per shell: 2

Electronic configuration: 1s²

So

It have 2 electrons in its outer (valance) shell and do not obey octet rule. although it is stable and obey duplet rule but not have true octet.

_____________________

3. Xenon (Xe)

Atomic No. 54

Electrons per shell: 2, 8, 18, 18, 8

Electronic configuration: [Kr] 4d¹⁰, 5s², 5p⁶

So

it have 8 electrons in its outer (valance) shell and obey octet rule

___________________

4. Neon (Ne)

Atomic No. 10

Electrons per shell: 2, 8

Electronic configuration: 1s², 2s², 2p⁶

So

it have 8 electrons in its outer (valance) shell and obey octet rule

___________________

So its only the hellium that do not have octet.

Nuclear fission

Hope I helped :)

The model illustrates the nuclear process of fission, where a larger nucleus splits into two or more smaller nuclei along with the release of energy.

Nuclear fission is the process illustrated, where a neutron causes a fissile atom like U-235 to split into smaller nuclei, releasing energy and more neutrons. During fission, the nucleus undergoes division, resulting in the production of additional particles and the liberation of energy.

The nuclear process illustrated by the model is nuclear fission. In nuclear fission, a neutron collides with a fissile atom like U-235, creating a heavier unstable isotope, in this case, U-236. This unstable nucleus then undergoes fission, splitting into smaller nuclei and releasing additional neutrons along with a significant amount of energy.

The liquid drop model proposed by Niels Bohr and John Wheeler explains this by comparing the nucleus to a droplet of water. When an external neutron impacts the uranium nucleus, it causes the nucleus to deform and eventually split, similar to a vibrating water droplet eventually breaking apart. The process can be tracked using nuclear symbols, and understanding it is crucial for applications like nuclear reactors where controlled fission is used for electricity generation.

Moreover, the models constructed to describe the nucleus should accurately reflect known nuclear properties and predict new properties that experiments might reveal. These predictions help in understanding nuclear processes such as fission in greater detail.

Answer:

The elements with the largest atomic radii are located towards the left and bottom of the periodic table (i.e. at the bottom of Group 1). Thus, in theory, the largest atom should be Francium.

it is Francium

Explanation:

well for starters this atom is call chlorine

and this has a total mass of 35.075 or sum like that so C .35

hope this helped you in any kinda way

Answer:

Supersaturated

Explanation:

Let's define the types of solutions in the context of this problem firstly:

We need to use a solubility curve for salts given below. Notice that the intersection in the y-axis at [tex]40^oC[/tex] is at about 14 g. This means a saturated solution would be obtained if 14 g of [tex]KClO_3[/tex] were dissolved in 100 g of water at this temperature. Anything above it would yield a supersaturated solution, below – an unsaturated solution.

Hence, we have a supersaturated solution.

Answer:

The number in C-12 and C-14 represent their atomic masses.

Explanation:

The number in C-12 and C-14 represent their atomic masses.

These two are the isotopes of carbon.

Isotopes of an element have same atomic number and different atomic masses due to different number of neutrons present.

An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.  All these three subatomic particles construct an atom.

All isotopes of carbon have same number of electrons and protons i.e, six

while C-14 has 8 neutrons and C-12 has six neutrons.

C-14 = 14-6 = 8

C-12 = 12-6 = 6

Thus sum of neutrons and protons is atomic mass that's why C-14 has 14 atomic mass (8+6=14) while C-12 has 12 atomic mass (6+6=12).

1. Meteorologist predict the weather by using tools. They use these tools to measure atmospheric conditions that occurred in the past and present, and they apply this information to create educated guesses about the future weather. The best we can do is observe past and present atmospheric patterns and data, and apply this information to what we think will happen in the future. Meteorologists use the scientific method on a daily – and even hourly – basis!

2. They use thermometers, barometers, sling psychrometers and rain gauges. They also use anemometers, hygrometers, weather maps, weather balloons and weather satellites.

Final answer:

Meteorologists make weather predictions by using weather stations and radar to gather data and analyze patterns in the atmosphere.

Explanation:

Meteorologists make weather predictions by using various tools to gather data and analyze patterns in the atmosphere.

Two types of weather tools commonly used by meteorologists are:

Weather stations: These are equipped with instruments such as barometers to measure air pressure, thermometers to measure temperature, and anemometers to measure wind speed and direction.

Radar: Weather radar uses radio waves to detect precipitation and track its movement. This information is crucial for predicting the path and intensity of storms.

By collecting data from these tools and analyzing it, meteorologists can make accurate weather predictions.

Answer:

ENERGY SOURCE

Explanation:

JUST TOOK QUIZ

The other person is right,

the answer is

(B) energy source

Hope this helps <3

Answer:

Advantages: More land has been made available for development. More buildings and infrastructure can be built, and also for other reasons.

Disadvantages: Much greenery has been removed in order for the land needed. Land reclamation can be damaging to corals and marine life. Corals are usually moved to another place when land is to be reclaimed. The corals might not be able to survive in that certain habitat, and thus die out. In some countries, where the project is large-scale, they do not even bother to re-plant the corals elsewhere, instead just reclaim the land on their habitat, causing them to die out immediately. Marine life, such as fishes, might not have enough food after the underwater plantations are destroyed due to reclamation of land. This applies to the food chain. The waters might also be polluted from the soil used to reclaim land, causing the fishes to die and blocking out sunlight, depriving the underwater plants of growth. Marine habitats are also destroyed, as mentioned earlier; therefore, the marine creatures would be forced to move to another new habitat. Some might not be able to adapt, and thus die out. Some would just die without even finding a new habitat, as they cannot move long distances in water. Of course, the reasons and examples look tempting to us humans, but marine life is life too! We should try to protect is as much as possible, instead of just focusing on the advantages.

Answer:

732.0601 mmHg

Explanation:

Given data:

Pressure = 97.6 KPa

Given pressure in mmHg = ?

Solution:

Kilo pascal and millimeter mercury both are units of pressure.

Kilo pascal is denoted as "KPa"

Millimeter mercury is denoted as " mmHg"

Kilo pascal is measure of force per unit area while also define as newton per meter square.

It is manometric unit of pressure. It is the pressure generated by column of mercury one millimeter high.

Conversation of kilopascal to mmHg:

97.6 × 7.501 = 732.0601 mmHg

Answer:

7.71 atm

Explanation:

Given the following data:

[tex]V = 5 L[/tex]

[tex]n_{He} = 3 mol[/tex]

[tex]n_{H_2} = 4 mol[/tex]

[tex]p_1 = 9 atm[/tex]

[tex]T = const[/tex]

According to the ideal gas law, we know that the product between pressure and volume of a gas is equal to the product between moles, the ideal gas law constant and the absolute temperature:

[tex]pV = nRT[/tex]

Since the temperature and the ideal gas constant are constants, as well as the fixed container volume of 5 L, we may rearrange the equation as:

[tex]\frac{p}{n}=\frac{RT}{V}=const[/tex]

This means for two conditions, we'd obtain:

[tex]\frac{p_1}{n_1}=\frac{p_2}{n_2}[/tex]

Given:

[tex]p_1 = 9 atm[/tex]

[tex]n_1 = n_{initial total} = n_{He} + n_{H_2} = 3 mol + 4 mol = 7 mol[/tex]

[tex]n_2 = n_{final total} = n_{He} + n_{H_2} = 3 mol + 4 mol + 2 mol = 9 mol[/tex]

Solve for the final pressure:

[tex]p_2 = p_1\cdot \frac{n_2}{n_1}[/tex]

Now, according to the Dalton's law of partial pressures, the partial pressure is equal to the total pressure multiplied by the mole fraction of a component:

[tex]p_{H_2}=\chi_{H_2}p_2[/tex]

Knowing that:

[tex]p_2 = p_1\cdot \frac{n_2}{n_1}[/tex]

And:

[tex]\chi_{H_2}=\frac{n_H_2}{n_2}[/tex]

The equation becomes:

[tex]p_{H_2}=\chi_{H_2}p_2=p_1\cdot \frac{n_2}{n_1}\cdot \frac{n_H_2}{n_2}=p_1\cdot \frac{n_H_2}{n_1}[/tex]

Substituting the variables:

[tex]p_{H_2}=9 atm\cdot \frac{4 mol + 2 mol}{7 mol}=7.71 atm[/tex]