What is the correct chronological order of scientists contributing to the modern periodic table? Lavoisier, Newlands, Moseley, Dobereiner, and Mendeleev Lavoisier, Dobereiner, Newlands, Mendeleev, and Moseley Moseley, Mendeleev, Newlands, Dobereiner, and Lavoisier

The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99%)

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Final answer:

In an exothermic reaction, the products have lower potential energy than the reactants, and the enthalpy change is negative. A process requires a negative enthalpy change and a positive entropy change to be spontaneous at all temperatures.

Explanation:

For an exothermic reaction, the correct statement is: The products have lower potential energy than the reactants, and the enthalpy change is negative. This is because an exothermic process involves the release of energy, typically in the form of heat, as the reactants transform into products. The products are more stable and lower in energy compared to the reactants, and the enthalpy change (ΔH) is negative, indicating that energy has been released to the surroundings.

For a process to be spontaneous at all temperatures, it must have a negative enthalpy change and a positive entropy change. This combination of factors means that the process is both energetically favorable and leads to an increase in the disorder or randomness of the system.

Photon is a packet of light energy. Both photon and electron contribute mostly to the quantum mechanics of the atom. Every particle in quantum mechanical model is explained as dual natured, that is has both particle and wave nature. Photons exhibit wave light properties like diffraction, interference, etc.,At the same time they exhibit particle properties like having a definite momentum and position. Similarly electrons and other microscopic particles exhibit both particle and wave nature.

Therefore, the correct answer is:

Both photons and electrons display particle and wave-like behaviour.

Answer:

+ 7.

Explanation:

We have general rules to assign the oxidation numbers:

Rule 1: The oxidation number of an element alone in its free (uncombined) state is zero.

For example, Al(s) or Zn(s).

This is also true for elements found in nature as diatomic (two-atom) elements  as: H₂, O₂, Cl₂, or I₂.

and also for sulfur, found as: S₈.

Rule 2: The oxidation number of a monatomic (one-atom) ion is the same as the charge on the ion,

For example:  Na⁺ = +1, S⁻² = -2.

Rule 3: The sum of all oxidation numbers in a neutral compound is zero. The sum of all oxidation numbers in a polyatomic (many-atom) ion is equal to the charge on the ion.

Rule 4: The oxidation number of an alkali metal (group IA) in a compound is +1; the oxidation number of an alkaline earth metal (group IIA) in a compound is +2.

Rule 5: The oxidation number of oxygen in a compound is usually –2.

If, however, the oxygen is in a class of compounds called peroxides.

(for example, hydrogen peroxide), then the oxygen has an oxidation number of –1. If the oxygen is bonded to fluorine, the number is +1.

So, for our problem Ca(MnO₄)₂:

∴ oxidation no. of Ca + 2[(oxidation no. of Mn) + 4(oxidation no. of O) = 0.

(+2) + 2[(oxidation no. of Mn) + (- 8)] = 0.

2[(oxidation no. of Mn) + (- 8)] = - 2.

[(oxidation no. of Mn) + (- 8)] = -1.

∴ (oxidation no. of Mn) = - 1 + 8 = + 7.

+7 is the oxidation number of manganese atom (Mn) in Ca(MnO₄)₂.

Oxidation number of any substance will tell about the import and export number of electrons from that substance.

Given compound is Ca(MnO₄)₂, this is a neutral compound means no charge is present on the compound. Oxidation number of Calcium (Ca) is +2, oxidation number of oxygen atom (O) is -2 and let the oxidation number of manganese (Mn) be x.

Total sum of the oxidation number of all atoms equals to the whole charge of the compound and calculation for oxidation number will be calculated as:

+2 + 2[x + 4(-2)] = 0

2 + 2x - 16 = 0

2x = 16 - 2

2x = 14

x = 7

Hence, +7 is the oxidation number.

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Answer:

drought

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The 3% mass/volume H₂O₂ means 3 g of H₂O₂ in 100 ml of water.

Now, Molarity (M) = No. of moles of H₂O₂ / Volume of solution in liter

No. of moles of H₂O₂ = Mass / Molar mass = 3 g / 34 g/mol = 0.088 mol

So, molarity = 0.088 × 1000 ml / 100 ml = 0.88 M

In case of 2.25 % H₂O₂,

No of moles = 2.25 g / 34 g/mol = 0.066 mol

Molarity = 0.066 mol / 0.100 L = 0.66 M.

The molarity of a 3.0% H₂O₂ solution is 0.88 M, and the molarity of a 2.25% H₂O₂ solution can be calculated using the same steps. The molarity of a solution is determined by dividing the moles of solute by the volume of the solution in liters.

The molarity of a solution is represented by the formula:

Molarity (M) = (moles of solute) / (volume of solution in liters)

First, we need to calculate the moles of H₂O₂ in each solution:

For the 3.0% H₂O₂ solution:

For the 2.25% H₂O₂ solution:

Now we can calculate the molarity of each solution:

For the 3.0% H₂O₂ solution: Molarity = 0.088 moles / 0.1 L = 0.88 M.

For the 2.25% H₂O₂  solution: Molarity = (moles of solute) / (volume of solution in liters).

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Answer:

20 L  

Step-by-step explanation:

Since temperature is constant, we can use Boyle’s Law.

p₁V₁ = p₂V₂    Divide each side by p₂

 V₂ = V₁ × p₁/p₂

=====

Data:

p₁ = 2.0 atm; V₁ = 35 L

p₂ = 3.5 atm; V₂ = ?

=====

Calculations:

V₂ = 35 × 2.0/3.5

V₂ = 20 L

Atomic mass (amu) = the number of protons and electrons

Atomic numbers = the little number on the periodic table that any element has which represents the number of protons in the nucleus

Atomic number is the number of protons that are inside that atom. This helps identify which element an atom is.

Atomic mass is the number of protons and neutrons inside an atom.

Question

Which one is more dangerous Ac or Dc how is it?

Answer

AC

_________________

AC has the voltage alternates, it enter and exit from your body without a closed loop.

The answer is; Relative dating

This type of dating is not concerned with determining the absolute age of rock. It compares between rock layer and determines which is younger or older in comparison. Therefore relative dating is significant in arranging geologic events based on the stratigraphy of rock layers.  

Answer: Relative dating

Explanation:

Relative dating is a technique of identifying the age of the material whether fossil or rocks by comparing them with the surrounding materials. This method takes into consideration the order of the geological events took place on earth. This can be done by stratigraphy. In stratigraphy the layers of the rocks and sediments are compared to determine the age of the object (fossil, rock). This method does not help in determining the exact or absolute age of the object.

Answer: a) [tex]\frac{28gN}{80gNH_4NO_ 3}\times 100\%[/tex]

Explanation: Mass percentage is defined as the ratio of the mass of the particular element to the total mass of the substance multiplied by 100.

[tex]{\text{mass percentage}=\frac{\text{mass of the element}}{\text{Total mass}}\times {100}[/tex]

mass of nitrogen[2 atoms of N] = 28 g

Total mass of [tex]NH_4NO_ 3=2\times {\text {Mass of nitrogen}}+4\times {\text {mass of hydrogen}}+3\times {\text {mass of oxygen}}[/tex]

[tex]=2\times 14+4\times 1 +3\times 16=80 g[/tex]

[tex]{\text{mass percentage}=\frac{28}{80}\times {100}\%[/tex]

The correct percent by mass of nitrogen in NH4NO3 is given by the expression 28 g N / 80 g NH4NO3 * 100%.

The expression that represents the percent by mass of nitrogen in NH4NO3 is determined by dividing the total mass of nitrogen in the compound by the total mass of the compound and then multiplying by 100%. Nitrogen has a molar mass of 14 g/mol, and there are two nitrogen atoms in NH4NO3. So, the total mass of nitrogen is 14 g/mol x 2 = 28 g/mol. Meanwhile, the molar mass of NH4NO3 is 80 g/mol. Therefore, the correct expression is 28 g N / 80 g NH4NO3 * 100%, or option (a).

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The intermolecular forces for Iodine are much lower than the energy needed to free it from its crystal lattice. Once Iodine has enough energy to break out of the lattice, it also has enough energy to separate from its neighbors. And so, it sublimes.

LiCi is an ionic compound, and ionic compounds are considered polar.

Answer: A The molten mixture of rock-forming substances, gases, and water from the mantle..

Explanation:

Final answer:

Utensils made of metal are typically homogeneous mixtures, while utensils made of plastic can be heterogeneous mixtures.

Explanation:

A utensil is not a substance but an object that is used to prepare or eat food. However, if you are referring to the materials that utensils are made of, such as metal or plastic, then they can be considered as mixtures. Utensils made of metal, for example, are typically a mixture of different metals, such as stainless steel or aluminum alloy. These metal mixtures can be considered as homogeneous mixtures because their composition is uniform throughout. On the other hand, utensils made of plastic can be considered as heterogeneous mixtures because they can have different additives and fillers mixed in with the plastic polymer.

Rubidium is a alkali metal.

Answer:

Rb is an alkali metal.

Explanation:

The elements characterized by having a single electron in its outermost orbital (s) are called alkali metals or simply alkaline metals.

Due to the presence of this electron, they are chemically very reactive because they have a tendency to lose this electron. In other words, their high reactivity is due to the fact that they form chemical bonds with many types of substances and elements and do so easily. This is due to its high electronegativity.

Like all metals, they are very good thermal and electrical conductors. But in comparison, alkali metals are soft and have a low melting point due to their metallic bond. This link is quite weak because it is the external electrons that are responsible for the bond and in these metals there is only one electron per atom.

The alkali metals are located in group 1 of the periodic table and are: lithium (Li), sodium(Na), potassium(K), rubidium(Rb), cesium(Cs) and francium(Fr).

Answer:

Its blue

Explanation:

Explanation: There are 2 given isotopes of Copper.

Mass number of Isotope 1 : 63amu

Mass number of Isotope 2: 65 amu

Let the fractional abundance of isotope 1 be 'x', so the fractional abundance for Isotope 2 will be '1-x'

The average atomic number of Copper given is 63.55 amu.

So, the formula for average atomic mass is given by:

[tex]\text{Average atomic mass of an element}=_{i=1}^n\sum{\text{atomic mass of isotopes}_i\times {\text {fractional abundance}_i}[/tex]

Putting values in above equation, we get:

[tex]63.55=[(63\times x)+(65\times (1-x))]\\\\x=0.725[/tex]

The fractional abundance of Isotope 1 = 0.725

The fractional abundance of Isotope 2 = 0.275

So, the natural percentage abundance for isotope 1 = 72.5%

The natural percentage abundance for isotope 2 = 27.5%

Whenever more number of isotopes are present of an element are present, we take the average atomic mass of that element.

time is usually on the x axis while position is on the y axis>

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Answer:

On a position-versus-time graph, along the x-axis (option b) is time usually shown.

Explanation:

One way to describe and study the movements is by means of graphs that represent distance-time (distance as a function of time), speed-time (speed as a function of time) and acceleration-time (acceleration as a function of time).

Then, as the displacements are made while time passes, the description of the movement is facilitated by making a graph of position versus time. In the vertical axis the positions that the body occupies are usually represented and in the horizontal axis the time. Similarly, velocity or acceleration can be represented versus time, where the horizontal axis is time and the vertical axis is velocity or acceleration.

Taking into account that the horizontal axis belongs to the x axis and the vertical axis to the y axis:

On a position-versus-time graph, along the x-axis (option b) is time usually shown.

Answer: Lanthanide and actinide series

Explanation: The elements with partially or fully filled f orbitals belong to f block elements.

f block elements include lanthanides and actinides. They are called so the lanthanides contain the first element named as lanthanum and actinides contain first element named as actinium. They are also called as inner transition elements.

All of them have general electronic configuration:

[tex](n-2)f^{1-14}(n-1)d^{0-10}ns^2[/tex], where n = 6-7

Answer: The very bottom row. Its like a light color orange.

Explanation: That's the f subleavel.

D I believe is the correct answer

Answer:

Option D

Wave A: Low Frequency Wave

Wave B: High Frequency Wave

The minimum temperature needed to dissolve 130 grams of [tex]KNO_{3}[/tex] in 100 grams of water is the solubility of [tex]KNO_{3}[/tex] at that particular temperature.

Solubility is the maximum amount of solute that can dissolve in a solvent at a given temperature. A [tex]KNO_{3}[/tex] solubility chart or data table must be used to estimate the minimum temperature needed to dissolve 130gm of [tex]KNO_{3}[/tex] in 100gm of water.

Given:

Mass of [tex]KNO_{3}[/tex] = 130 gm,

Mass of water = 100 gm.

Let's assume that the solubility of [tex]KNO_{3}[/tex] in 100gm of water is 80gm at 20°C. The solubility limit will be exceeded (130gm > 80gm) if we attempt to dissolve 130gm of [tex]KNO_{3}[/tex] in 100gm of water at 20°C, producing an unsaturated solution. To find the minimum temperature needed for complete dissolution, we need to find the temperature at which the solubility of [tex]KNO_{3}[/tex] is equal to or greater than 130gm. If we refer to the solubility chart and find that at 30°C, the solubility of [tex]KNO_{3}[/tex] is 130gm in 100gm of water, then the minimum temperature required is 30°C.

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Answer:

Name = name of metal + hydroxide.  

Step-by-step explanation:

You name an ionic base according to the rule:

Name = name of metal + hydroxide

Thus,  

  NaOH = sodium hydroxide

Ca(OH)₂ = calcium hydroxide

Al(OH)₃ = aluminium hydroxide

The greatest number of valence electrons available for bondinging is Chlorine.

Chlorine has the greatest number of valence electrons available for bonding among the options provided, with seven valence electrons as it is a halogen from Group 7A.

The element with the greatest number of valence electrons available for bonding among the options given is Chlorine. Chlorine belongs to Group 7A of the periodic table, which contains the halogens. All halogens, including chlorine, have seven valence electrons and thus can form bonds by accepting an electron to achieve a full octet. Comparatively, Selenium, although it can expand its octet, typically has six valence electrons, while Boron has three, and Calcium has two in their outermost energy level.

Specifically certain Group 7A elements are known to exist in nature as diatomic molecules, such as F2, Cl2, Br2 and I2, indicating their strong tendency to bond with themselves or other elements. Moreover, fluorine, also a halogen, is known to have the highest electronegativity, implying a strong attraction for electrons to form bonds. This same logic applies to chlorine as well, though it is slightly less electronegative than fluorine. Thus, out of the options listed, chlorine is the element that has the most valence electrons ready to partake in bonding.

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Generally for simpler salts like sodium chloride, when the salts gets dissolved in water the temperature slightly decreases. But for salts which comes in the form of pellets which are more exothermic increases the temperature of water. The increase or decrease in the temperature depends upon the type of salt that is dissolved in the water.

Balanced forces means the forces acting on the object are either equal but in opposite directions or zero.

For the first option, something starting to roll means it has an unbalanced force acting on it.

For the second option, these forces are equal and in opposite directions, so these are balanced forces.

For the third option, the forces are not equal and not in opposite directions, so these are unbalanced forces.

And for the last option, something that changes speed does not have balanced forces.

The questions pertain to the effects of forces on an object (a marble) within the field of physics. The first involves combining two forces acting in different directions, and the second involves Newton's first law of motion.

The subject of these questions pertains to force and its effects, specifically in the context of physics. In the first scenario, we're looking at the combination of two forces on an object (the marble). The 2-N force pressing down and 1.5-N force acting to the right will result in a net force at an angle, according to vector addition. In the second scenario, the concept of Newton's first law of motion comes into play. The marble, initially in motion, comes to rest when it hits the garden wall because an external force (the wall) is applied, disrupting its initial state of motion.

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The mass of C2H2 produced by the reaction of 3.75g of CaC2 can be calculated using the balanced chemical equation and the molar masses of CaC2 and C2H2. The number of moles of CaC2 and C2H2 can be determined, and then multiplied by their respective molar masses to find the mass of C2H2 produced.

To answer the question, we need to use the balanced chemical equation for the reaction between calcium carbide (CaC2) and water (H2O):

CaC2 (s) + 2H2O (l) → C2H2 (g) + Ca(OH)2 (s)

From the equation, we can see that 1 mole of calcium carbide reacts to produce 1 mole of acetylene gas.

Now, we need to calculate the number of moles of calcium carbide using its molar mass:

Molar mass of CaC2 = 40.08 g/mol + 12.01 g/mol × 2 = 64.10 g/mol

Mass of CaC2 = 3.75

Number of moles of CaC2 = Mass of CaC2 / Molar mass of CaC2 = 3.75 g / 64.10 g/mol = 0.0585 mol

Since 1 mole of CaC2 produces 1 mole of C2H2, the number of moles of C2H2 produced is also 0.0585 mol.

Finally, we can calculate the mass of C2H2 produced using its molar mass:

Molar mass of C2H2 = 12.01 g/mol × 2 + 1.01 g/mol × 2 = 26.04 g/mol

Mass of C2H2 = Number of moles of C2H2 × Molar mass of C2H2 = 0.0585 mol × 26.04 g/mol = 1.52 g

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