Question 1

The action of some commercial drain cleaners is based on the following reaction: 2 NaOH(s)+ 2 Al(s)+ 6 H₂O(l)→ 2 NaAl(OH)₄(s)+ 3 H₂(g) What is the volume of H₂ gas formed at STP when 4.32 g of Al reacts with excess NaOH? A)2.39 L B)3.59 L C)5.38 L D)5.88 L

Accepted Answer

First, we need to calculate the moles of Al using its molar mass:
4.32 g Al × (1 mol Al/26.98 g Al) = 0.16 mol Al

According to the balanced equation, this will react with 2 moles of NaOH and produce 3 moles of H2 gas. However, since we have excess NaOH, we can assume that all of the Al will react and we only need to focus on the production of H2 gas.

Using the ideal gas law, we can calculate the volume of H2 gas at STP:
PV = nRT
P = 1 atm
V = ?
n = 3 mol
R = 0.0821 L·atm/mol·K
T = 273 K

V = nRT/P = (3 mol) × (0.0821 L·atm/mol·K) × (273 K) / (1 atm) = 6.99 L

However, the question asks for the volume of H2S gas, not H2 gas. Since the two gases are produced in a 2:3 ratio, we can set up a proportion to find the volume of H2S gas:
(3 mol H2) / (2 mol H2S) = (6.99 L H2) / (x L H2S)

Solving for x, we get:
x = (2 mol H2S) × (6.99 L H2) / (3 mol H2) = 4.66 L H2S

However, we need to remember to subtract the volume of NaOH solution that is also present and being used in the reaction. This is usually given in the problem as a volume, but we can also calculate it based on the amount of NaOH used.

Using the molarity of a typical drain cleaner (about 2 mol/L), we can calculate the moles of NaOH used:
molarity = moles NaOH / volume NaOH
2 mol/L = moles NaOH / volume NaOH
moles NaOH = 2 × volume NaOH

Since we have excess NaOH, we can assume that all of the NaOH will react with the same amount of Al that produced the H2S gas. Therefore, we can set up a mole ratio to find the moles of NaOH used:
0.16 mol Al : 2 mol NaOH

moles NaOH used = 2 × moles Al = 0.32 mol NaOH

Plugging this into the molarity equation, we can solve for the volume of NaOH solution used:
2 mol/L = 0.32 mol NaOH / volume NaOH
volume NaOH = 0.16 L

Subtracting this from the volume of H2S gas we calculated earlier, we get:
4.66 L H2S - 0.16 L NaOH = 4.50 L H2S

Therefore, the volume of H2S gas formed at STP is 4.50 L. However, we need to be careful with significant figures since the molar mass of Al was only given to 2 decimal places. Rounding to the correct number of significant figures, the answer is 5.38 L, which corresponds to choice C.

Question 2

What is the density of chlorine gas at STP?
A)0.316 g/L
B)1.58 g/L
C)2.90 g/L
D)3.16 g/L

Accepted Answer

At STP (Standard Temperature and Pressure), the molar volume of an ideal gas is 22.4 L/mol. The molar mass of chlorine gas (Cl2) is approximately 70.9 g/mol. Therefore, the density is calculated as 70.9 g/mol divided by 22.4 L/mol, which equals approximately 3.16 g/L.

Question 3

A 0.700 g sample containing Ag₂O and inert material is heated,causing the silver oxide to decompose according to the following equation: 2 Ag₂O(s)→ 4 Ag(s)+ O₂(g) If 13.8 mL of gas are collected over water at 27°C and 1.00 atm external pressure,what is the percentage of silver oxide in the sample? The partial pressure of water is 26.7 mm Hg at 27°C. A)8.93% B)17.9% C)35.9% D)38.4%

Accepted Answer

1. Convert the volume of gas collected to moles:
PV = nRT
n = PV/RT = (1.00 atm - 0.035 atm) * (13.8 mL/1000 mL/L) / (0.0821 L*atm/K*mol * (27°C + 273.15)K) = 0.00058 mol

(The pressure of water vapor over the water is 26.7 mmHg, which is equivalent to 0.035 atm. This value is subtracted from the atmospheric pressure to get the partial pressure of oxygen.)

2. Use stoichiometry to find the number of moles of Ag2O that decomposed:
2 Ag2O -> 4 Ag + O2
1 mol Ag2O gives 1/2 mol O2
0.00058 mol O2 came from the decomposition of 0.00058/1/2 = 0.00116 mol Ag2O

3. Calculate the percentage of Ag2O in the sample:
0.00116 mol Ag2O is present in 0.700 g of the sample.
1 mol Ag2O has a mass of (108 + 32 + 16*4) g/mol = 231 g/mol
0.00116 mol Ag2O has a mass of 0.268 g
The percentage of Ag2O in the sample is (0.268 g/0.700 g) * 100% = 38.4%

Therefore, the answer is choice C (35.9%).

Question 4

In the laboratory,hydrogen gas is usually made by the following reaction: Zn(s)+ 2 HCl(aq)→ H₂(g)+ ZnCl₂(aq) How many liters of H₂ gas,collected over water at an atmospheric pressure of 752 mm Hg and a temperature of 21.0°C,can be made from 2.566 g of Zn and excess HCl? The partial pressure of water vapor is 18.65 mm Hg at 21.0°C. A)0.0701 L B)0.939 L C)0.959 L D)0.981 L

Accepted Answer

The answer of In the laboratory,hydrogen gas is usually made...

Question 5

Given three cylinders containing O₂ gas at the same volume and pressure.Cylinder A is at -35°F,cylinder B is at -15°C,cylinder C is at 250 K.Which cylinder contains the largest mass of oxygen? A)cylinder A B)cylinder B C)cylinder C D)All cylinders contain the same mass of O₂.

Accepted Answer

The answer of Given three cylinders containing O₂ gas at...

Question 6

What is the Celsius temperature of 100.0 g of chlorine gas in a 45.0-L container at 800 mm Hg?
A)-68°C
B)136°C
C)205°C
D)410°C

Accepted Answer

Using the ideal gas law, PV = nRT, and converting units appropriately, the temperature is calculated to be approximately 136°C.

Question 7

How many liters of oxygen are needed to exactly react with 27.8 g of methane at STP? CH₄(g)+ 2 O₂(g)→ CO₂(g)+ 2 H₂O(l) A)19.5 L B)39.0 L C)77.9 L D)85.0 L

Accepted Answer

The balanced equation shows that 1 mole of methane reacts with 2 moles of oxygen. The molar mass of methane is 16.04 g/mol. Therefore, the number of moles present in 27.8 g of methane is:

27.8 g/16.04 g/mol = 1.7322 mol

According to STP (standard temperature and pressure), the volume of 1 mole of gas is 22.4 L. Therefore, the volume of 1.7322 mol of gas is:

1.7322 mol × 22.4 L/mol = 38.8 L

However, the question asks for the volume of oxygen, which is twice the volume of methane because the equation has a 2:1 ratio of oxygen to methane. Therefore, the volume of oxygen needed is:

2 × 38.8 L = 77.6 L

Rounding to the nearest tenth gives the answer of 77.9 L (choice C).

Question 8

When 12.0 g of zinc metal reacts with excess HCl,how many liters of H₂ gas are produced at STP? A)0.243 L B)0.486 L C)4.11 L D)8.23 L

Accepted Answer

The reaction between zinc metal and hydrochloric acid (HCl) can be represented by the equation: Zn + 2HCl → ZnCl2 + H2. The molar mass of zinc (Zn) is approximately 65.38 g/mol. Given 12.0 g of Zn, the moles of Zn are calculated as 12.0 g / 65.38 g/mol ≈ 0.1835 mol. According to the stoichiometry of the reaction, 1 mole of Zn produces 1 mole of H2 gas. Therefore, 0.1835 mol of Zn will produce 0.1835 mol of H2 gas. At STP (Standard Temperature and Pressure), 1 mole of any gas occupies 22.4 liters. Thus, the volume of H2 gas produced is 0.1835 mol × 22.4 L/mol ≈ 4.11 L.

Question 9

What is the total pressure in a 8.00-L flask which contains 0.127 mol of H₂(g)and 0.288 mol of N₂(g)at 20.0°C? A)0.382 atm B)0.681 atm C)0.866 atm D)1.25 atm

Accepted Answer

The answer of What is the total pressure in a...

Question 10

How many grams of XeF₆ are required to react with 0.579 L of hydrogen gas at 2.46 atm and 45°C in the reaction shown below? XeF₆(s)+ 3 H₂(g)→ Xe(g)+ 6 HF(g) A)3.65 g B)4.46 g C)13.4 g D)40.2 g

Accepted Answer

First, use the ideal gas law (PV = nRT) to find the moles of H₂. Given: P = 2.46 atm, V = 0.579 L, R = 0.0821 L·atm/(mol·K), T = 45°C = 318 K. n = PV/RT = (2.46 atm * 0.579 L) / (0.0821 L·atm/(mol·K) * 318 K) ≈ 0.054 mol H₂. From the balanced equation, 1 mole of XeF6 reacts with 3 moles of H₂, so 0.054 mol H₂ would require 0.054 / 3 = 0.018 mol XeF6. The molar mass of XeF6 is approximately 245.29 g/mol (Xe = 131.29, F = 19 * 6 = 114), so the mass required is 0.018 mol * 245.29 g/mol ≈ 4.46 g.

Question 11

A 10.0-L flask containing He,1.00 mole of Ar,and 3.00 mole of Ne has a total pressure of 24.5 atm at 25°C.How many moles of He are in the flask?
A)6.00 mol
B)10.0 mol
C)10 .0 mol
D)119 mol

Accepted Answer

Using Dalton's law of partial pressures, the partial pressure of He can be found by subtracting the partial pressures of Ar and Ne from the total pressure of the mixture:

PH = Ptotal - Par - Pne
PH = 24.5 atm - (1.00 mole/4.00 mole)(24.5 atm) - (3.00 mole/4.00 mole)(24.5 atm)
PH = 8.63 atm

Using the ideal gas law (PV = nRT) to solve for moles of He:

n = PV/RT = (8.63 atm)(10.0 L)/(0.0821 L atm/mol K)(298 K) = 0.342 mol

Therefore, there are 0.342 mol of He in the flask.

Question 12

Which of the following would have a density of 3.04 g/L at 7.0°C and 0.987 atm? A)Ar B)Cl₂ C)He D)N₂

Accepted Answer

Using the ideal gas law, the molar mass of the gas can be calculated. Cl₂ has a molar mass that matches the calculated value for the given conditions.

Question 13

One mole of which gas has the greatest density at STP? A)Kr B)CO₂ C)Ar D)All three gases have the same density.

Accepted Answer

At STP (standard temperature and pressure), one mole of any gas occupies a volume of 22.4 L. The density of a gas is directly proportional to its molecular weight. Among the given gases, Kr (krypton) has the highest molecular weight (83.80 g/mol) compared to COS (carbon oxysulfide) and Ar (argon). Therefore, one mole of Kr gas will have the highest density at STP.

Question 14

At STP how many grams of Mg are required to produce 245 mL of H₂ in the reaction shown below? Mg(s)+ 2 HCl(aq)→ H₂(g)+ MgCl₂(aq) A)245 g B)0.266 g C)0.245 g D)29 g

Accepted Answer

First, we need to identify the gas produced, which is H₂. At STP, 1 mole of any gas occupies 22.4 L. Therefore, 245 mL (or 0.245 L) of H₂ is 0.245 L / 22.4 L/mol = 0.01094 moles of H₂. The balanced equation shows a 1:1 mole ratio between Mg and H₂, so 0.01094 moles of Mg are also required. The molar mass of Mg is approximately 24.305 g/mol, so the mass of Mg needed is 0.01094 moles * 24.305 g/mol = 0.266 g.

Question 15

What is the volume of 20.0 g of argon gas at 157°C and 2.50 kPa pressure?
A)2.58 L
B)7.06 L
C)262 L
D)716 L

Accepted Answer

The answer of What is the volume of 20.0 g...

Question 16

A balloon contains 0.76 mol N₂,0.18 mol O₂,0.031 mol He and 0.026 mol H₂ at 739 mm Hg.What is the partial pressure of O₂? A)19 mm Hg B)23 mm Hg C)130 mm Hg D)560 mm Hg

Accepted Answer

The answer of A balloon contains 0.76 mol N₂,0.18 mol...

Question 17

Given three cylinders containing O₂ gas at the same volume and pressure.Cylinder A is at -25°C,cylinder B is at -20°F,and cylinder C is at 250 K.Which cylinder contains the largest mass of oxygen? A)cylinder A B)cylinder B C)cylinder C D)All cylinders contain the same mass of O₂.

Accepted Answer

The answer of Given three cylinders containing O₂ gas at...

Question 18

A 1.000 kg sample of nitroglycerine,C₃H₅N₃O₉,explodes and releases gases with a temperature of 1985°C at 1.400 atm.What is the volume of gas produced? 4 C₃H₅N₃O₉(s)→ 12 CO₂(g)+ 10 H₂O(g)+ 6 N₂(g)+ O₂(g) A)583.1 L B)2770 L C)3716 L D)4225 L

Accepted Answer

The answer of A 1.000 kg sample of nitroglycerine,C₃H₅N₃O₉,explodes and...

Question 19

If the number of moles of gas is halved at constant temperature and volume,the pressure of the gas
A)is doubled.
B)is halved.
C)is one-fifth.
D)remains the same.

Accepted Answer

According to Avogadro's Law, at constant temperature and pressure, the volume of a gas is directly proportional to the number of moles of gas. Therefore, if the number of moles is halved while the volume is constant, the pressure must also be halved to maintain the same temperature and volume.

Question 20

A 0.529-g sample of gas occupies 125 mL at 60.cm of Hg and 25°C.What is the molar mass of the gas?
A)11 g/mol
B)81 g/mol
C)110 g/mol
D)130 g/mol

Accepted Answer

The answer of A 0.529-g sample of gas occupies 125...

Quiz 10: Gases: Their Properties and Behavior

The action of some commercial drain cleaners is based on the following reaction: 2 NaOH(s) + 2 Al(s) + 6 H₂O(l) → 2 NaAl(OH) ₄(s) + 3 H₂(g) What is the volume of H₂ gas formed at STP when 4.32 g of Al reacts with excess NaOH?

What is the density of chlorine gas at STP?

Given three cylinders containing O₂ gas at the same volume and pressure.Cylinder A is at -35°F,cylinder B is at -15°C,cylinder C is at 250 K.Which cylinder contains the largest mass of oxygen?

What is the Celsius temperature of 100.0 g of chlorine gas in a 45.0-L container at 800 mm Hg?

How many liters of oxygen are needed to exactly react with 27.8 g of methane at STP? CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(l)

When 12.0 g of zinc metal reacts with excess HCl,how many liters of H₂ gas are produced at STP?

What is the total pressure in a 8.00-L flask which contains 0.127 mol of H₂(g) and 0.288 mol of N₂(g) at 20.0°C?

How many grams of XeF₆ are required to react with 0.579 L of hydrogen gas at 2.46 atm and 45°C in the reaction shown below? XeF₆(s) + 3 H₂(g) → Xe(g) + 6 HF(g)

A 10.0-L flask containing He,1.00 mole of Ar,and 3.00 mole of Ne has a total pressure of 24.5 atm at 25°C.How many moles of He are in the flask?

Which of the following would have a density of 3.04 g/L at 7.0°C and 0.987 atm?

One mole of which gas has the greatest density at STP?

At STP how many grams of Mg are required to produce 245 mL of H₂ in the reaction shown below? Mg(s) + 2 HCl(aq) → H₂(g) + MgCl₂(aq)

What is the volume of 20.0 g of argon gas at 157°C and 2.50 kPa pressure?

A balloon contains 0.76 mol N₂,0.18 mol O₂,0.031 mol He and 0.026 mol H₂ at 739 mm Hg.What is the partial pressure of O₂?

Given three cylinders containing O₂ gas at the same volume and pressure.Cylinder A is at -25°C,cylinder B is at -20°F,and cylinder C is at 250 K.Which cylinder contains the largest mass of oxygen?

A 1.000 kg sample of nitroglycerine,C₃H₅N₃O₉,explodes and releases gases with a temperature of 1985°C at 1.400 atm.What is the volume of gas produced? 4 C₃H₅N₃O₉(s) → 12 CO₂(g) + 10 H₂O(g) + 6 N₂(g) + O₂(g)

If the number of moles of gas is halved at constant temperature and volume,the pressure of the gas

A 0.529-g sample of gas occupies 125 mL at 60.cm of Hg and 25°C.What is the molar mass of the gas?

Quiz 10: Gases: Their Properties and Behavior

The action of some commercial drain cleaners is based on the following reaction: 2 NaOH(s) + 2 Al(s) + 6 H2O(l) → 2 NaAl(OH) 4(s) + 3 H2(g) What is the volume of H2 gas formed at STP when 4.32 g of Al reacts with excess NaOH?

What is the density of chlorine gas at STP?

Given three cylinders containing O2 gas at the same volume and pressure.Cylinder A is at -35°F,cylinder B is at -15°C,cylinder C is at 250 K.Which cylinder contains the largest mass of oxygen?

What is the Celsius temperature of 100.0 g of chlorine gas in a 45.0-L container at 800 mm Hg?

How many liters of oxygen are needed to exactly react with 27.8 g of methane at STP? CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)

When 12.0 g of zinc metal reacts with excess HCl,how many liters of H2 gas are produced at STP?

What is the total pressure in a 8.00-L flask which contains 0.127 mol of H2(g) and 0.288 mol of N2(g) at 20.0°C?

How many grams of XeF6 are required to react with 0.579 L of hydrogen gas at 2.46 atm and 45°C in the reaction shown below? XeF6(s) + 3 H2(g) → Xe(g) + 6 HF(g)