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The mass of H2(g) collected is approximately calculated as 0.582 grams. This result is found by subtracting the water's vapor pressure from the total pressure, applying the ideal gas law to find the number of moles, and converting moles to grams.

To calculate the mass of H2(g) collected, we'll first need to calculate the pressure of the dry hydrogen gas. The pressure of a gas collected over water is a sum of the pressure of the dry gas and the vapor pressure of the water. Hence, the pressure of dry H2(g) is the total pressure minus the water vapor pressure, so 685 mmHg - 18.6 mmHg = 666.4 mmHg.

Next, we convert this pressure into atmospheres: 666.4 mmHg * (1 atm / 760 mmHg) = 0.877 atm (approximately). We'll also need to convert the temperature to Kelvin: 21ºC + 273 = 294 K.

Then, we can use the ideal gas law, PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant (0.0821 L*atm/K*mol), and T is temperature. Solving for n, n = PV / RT, we substitute the known values to get n = (0.877 atm * 7.80 L) / (0.0821 L*atm/K*mol * 294 K) = 0.291 mol.

Last, we turn moles of H2 into grams. As the molar mass of H2(g) is approximately 2 g/mol, the mass of H2(g) collected is 0.291 mol * 2 g/mol = 0.582 grams.

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The correct answers are:

1. B. Mg loses two electrons.

When Mg and Br combine, 2 atoms of Br attaches itself to Mg. The chemical reaction is:

Mg + Br ---> MgBr2

Since Br is more electronegative than Mg, then Mg loses an electron per Br therefore losing 2 electrons.

2. D. An atom that gains electrons must be attracted to an atom that loses electrons.

An ionic bond is formed when one molecule is more electronegative than the other molecule which results in gaining and losing of electrons. The more electronegative molecule gains electron while the less electronegative loses electron.

In the formation of an ionic bond between magnesium and bromine, magnesium loses two electrons to become a Mg₂ + ion, and these oppositely charged ions attract each other to form the bond.

Understanding Ionic Bonds between Magnesium and Bromine:

1. When an ionic bond forms between magnesium (Mg) and bromine (Br), the process involves a transfer of electrons. Specifically, Mg loses two electrons (Option B) to achieve a stable electron configuration similar to the nearest noble gas. As a result, magnesium becomes a Mg₂+ ion.

2. For an ionic bond to form, there must be a transfer of electrons from one atom to another, leading to the formation of ions with opposite charges, which are then attracted to each other (Option D). An atom with a lower electronegativity, like magnesium, will lose electrons and become a positively charged cation. Conversely, an atom with higher electronegativity will gain electrons and become a negatively charged anion, such as bromine becoming Br-.

Soaps are made by the process saponification. Soaps contains long chain fatty acids and glycerol. The oily nature of soaps are due the presence of fatty acids.

Saponification is the process, making of soaps from glycerol and fatty acids. Therea are different types of soaps based on the ionic nature of the long chain fatty acids.

There are alkaline soaps in which the acidic chain possess a negatively charged group and acidic soaps are those bearing positively charged ions. The nature of sopas can be varied as per the use also.

Fatty acids are long chain hydrocarbons formed by the combination of simple hydrocarbons and they will reacts easily with alcohols forming esters of fatty acids that are soaps.

Hence, the presence of fatty acids make the soaps oily in nature and move gains friction in our hand.

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Electronegativity in water creates partial charges, causing polarity. This polarity allows hydrogen bonding between water molecules, enhancing interactions.

In a water molecule (H₂O), oxygen is more electronegative than hydrogen. This means that oxygen attracts the shared electrons in the O-H bonds more strongly than hydrogen does.

As a result, the electrons spend more time closer to the oxygen atom, giving it a partial negative charge (δ−), while the hydrogen atoms acquire a partial positive charge (δ+). This uneven distribution of charge creates a dipole moment, making water a polar molecule.

The polarity of water molecules causes them to be attracted to each other. The partial positive charge of one water molecule is attracted to the partial negative charge of another, forming hydrogen bonds.

These bonds are relatively weak compared to covalent bonds but are crucial for water’s unique properties, such as its high boiling point and surface tension.

The freezing point of the solution is 0.88°C

The melting point of a substance which is also the same as the freezing point is the temperature at which it changes from a solid state to a liquid state at a specific pressure. At the melting point, the substance absorbs heat energy, increasing its temperature and causing the solid structure to break down

We have that;

Number of moles of naphthalene = 10 g/128 g/mol

= 0.078 moles

Mass of benzene = Density * volume

= 0.877 g/cm3 * 100.0 mL

= 87.7 g or 0.0877 Kg

Where;

ΔT = K m i

ΔT = 5.12 *  0.078 moles/ 0.0877 Kg * 1

= 4.6°C

ΔT = Freezing point of pure solvent - Freezing point of solution

Freezing point of solution = 5.48°C - 4.6°C

= 0.88°C

Missing parts

Calculate the freezing point and melting point of a solution containing 10.0 g of naphthalene (C10H8) in 100.0 mL of benzene. Benzene has a density of 0.877 g/cm3

Answer: The correct answer is [tex]3.6\times 10^{-6}[/tex]

Explanation:

We are given:

Acid dissociation constant [tex](k_a)=2.8\times 10^{-9}[/tex]

Water dissociation constant [tex](k_w)=1\times 10^{-14}[/tex]

To calculate the base dissociation constant for the conjugate base, we use the equation:

[tex]k_w=k_a\times k_b[/tex]

where,

[tex]k_b[/tex] = base dissociation constant

Putting values in above equation, we get:

[tex]10^{-14}=2.8\times 10^-9}\times k_b\\\\k_b=3.6\times 10^{-6}[/tex]

Hence, the correct answer is [tex]3.6\times 10^{-6}[/tex]

Answer:

5 subshells

Explanation:

Answer: Option (D) is the correct answer.

Explanation:

When there is minimum use of energy and we are still able to preserve resources then it means we are cutting the demand for energy.

Therefore, when we are treating water with chlorine then it means without any electricity or energy we are cleaning the water. But at the same time chlorinated water is harmful to use unless chlorine is dissolved in limiting quantity.

Whereas energy efficient appliances will use the electricity efficiently.

Landfill will require the use of machines or man power therefore, energy will be used.

On the other hand, when rules are framed against the use of chlorofluorocarbons then there will be lesser depletion of ozone layer. Hence, use of energy will be minimum.

Thus, we can conclude that legislation against the use of chlorofluorocarbons has helped preserve resources while cutting the demand for energy.

HCHO2 and NaCHO2, and CH3NH2 and CH3NH3Cl can make buffer solutions. HCl and NaCl, and NH3 and NaOH cannot make buffer solutions.

1. HCHO2 is formic acid, a weak acid, while NaCHO2 is the salt made from the anion of the weak acid (the formate ion [CHO2]). The combination of these two solutes would make a buffer solution.

2. HCl is a strong acid, not a weak acid, so the combination of these two solutes would not make a buffer solution.

3. CH3NH2 is methylamine, which is like NH3 with one of its H atoms substituted with a CH3 group. Because it is not listed in Table 12.8.1, we can assume that it is a weak base. The compound CH3NH3Cl is a salt made from that weak base, so the combination of these two solutes would make a buffer solution.

4. NH3 is a weak base, but NaOH is a strong base. The combination of these two solutes would not make a buffer solution.

This is a problem based on concept of first law of thermodynamics

if a body is giving heat it will be absorbed by some other body or surrounding.

Now we have taken metal at low temperature and water at high temperature

So water will lose some energy and the same amount of energy will be gained by metal. The exchange will continue untill both reach the same temperature.

So answer is

The energy gained by the metal equals the energy lost by the water.

To find the luminous intensity this formula is used;

Luminous intensity = illuminance ×  [tex]radius ^{2}[/tex]

∴ Lv = Ev × [tex] r^{2}[/tex]

We know the luminous intensity is 100 candelas and the illuminance is 4 lux.

∴ 100 = 4 x  [tex] r^{2}[/tex]

∴ 100/4 =  [tex] r^{2}[/tex]

∴ 25 =  [tex] r^{2}[/tex]

∴ r =√25 = 5 meters

Therefore, the surface will be at a distance of 5 meters from the source.

To convert 2,150 mmHg to kPa, divide by the conversion factor 7.5 mmHg, resulting in approximately 286 kPa.

A conversion factor is a mathematical ratio that allows you to convert from one unit of measurement to another. It is often used to change units within the same system (e.g., converting inches to centimeters) or between different systems (e.g., converting miles to kilometers) by multiplying or dividing by the appropriate factor.

To convert from millimetres of mercury (mmHg) to kilopascals (kPa), you can use the conversion factor:

1 kPa = 7.5 mmHg

First, divide 2,150 mmHg by the conversion factor:

= 2,150 mmHg / 7.5 mmHg

= 286.67 kPa

Rounding to the nearest hundredth, the answer is approximately 286 kPa.

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Final answer:

To find the limiting reagent between hydrogen and oxygen, we convert their masses to moles and use the stoichiometry of the balanced chemical reaction 2 H2 + O2 → 2 H2O. Oxygen is the limiting reagent because there are not enough moles of O2 to fully react with the available moles of H2.

Explanation:

To determine the limiting reagent when 4.0 g of hydrogen (H2) and 10.0 g of oxygen (O2) are mixed to react according to the equation 2 H2 + O2 → 2 H2O, we need to perform mass-mole calculations for both reactants and compare the stoichiometry of the balanced equation.

First, convert the mass of each reactant to moles:

For H2: Molecular weight is approximately 2.02 g/mol. Thus, 4.0 g H2 ÷ 2.02 g/mol = 1.98 moles of H2.

For O2: Molecular weight is approximately 32.00 g/mol. Thus, 10.0 g O2 ÷ 32.00 g/mol = 0.3125 moles of O2.

According to the balanced equation, 2 moles of H2 react with 1 mole of O2. Therefore, to fully react with 1.98 moles of H2, we would need 0.99 moles of O2. However, we only have 0.3125 moles of O2, which is insufficient to react with all the H2. Therefore, O2 is the limiting reagent.

The balanced thermochemical equation for the decomposition of methanol (CH3OH(g)) to form CH4(g) and O2(g) is CH3OH(g) -> CH4(g) + O2(g) + 252.8 kJ/mol of O2 formed.

The balanced thermochemical equation for the decomposition of methanol (CH3OH(g)) to form CH4(g) and O2(g) can be written as:

CH3OH(g) -> CH4(g) + O2(g) + 252.8 kJ/mol of O2 formed.

Answer:

c

Explanation:

Answer:

[tex]\rm PbSO_4[/tex] will precipitate in the given reaction.

Explanation:

The reaction takes place between lead nitrate [tex]\rm Pb(NO_3)_2[/tex] and potassium sulphate [tex]\rm K_2SO_4[/tex].

Now, the reaction will be a double displacement reaction in which the ions will exchange between lead nitrate [tex]\rm Pb(NO_3)_2[/tex] and potassium sulphate [tex]\rm K_2SO_4[/tex].

So, the chemical reaction can be written as,

[tex]\rm {Pb(NO_3)_2+K_2SO_4}\rightarrow PbSO_4+2KNO_3[/tex]

In the above equation, [tex]\rm PbSO_4[/tex] is a precipitate which will be settled down in the  bottom and [tex]\rm KNO_3[/tex] will form an aqueous solution.

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Answer:

Explanation:

Kinetic energy is the energy possessed by an object by virtue of its motion.

Average kinetic energy is defined as the average of the kinetic energies of all the particles present in a system. It is determined by the equation:

[tex]K=\frac{3nRT}{2}[/tex]

K= kinetic energy

n= number of moles

R= gas constant

T= temperature  

[tex]4265J=\frac{3\times 1\times\times 8.314\times T}{2}[/tex]

[tex]T=342K[/tex]

[tex]tK=(t-273)^0C[/tex]

[tex]T=342K=(342-273)^0C=69^0C[/tex]

Thus temperature will be [tex]69^0C[/tex]