Q: A sample of nitrogen gas ($$\mathrm{N_2$}) $$has a volume of $$11.2\ \mathrm{L} at $$STP. How many molecules are present in this sample?

$$\displaystyle 3.01 \times 10$$^{23}$$

Question 1

8.00 g of hydrogen gas ($$\mathrm{H_2$}) $$are combined with an excess amount of oxygen gas ($$\mathrm{O_2$}) to $$produce water vapor at 1 atm of pressure and a temperature of 273 K. How many liters of water vapor are produced?

Accepted Answer

$$\displaystyle 44.8\ \mathrm{L}$$

Question 2

Ammonium sulfate, an important fertilizer, can be prepared by the reaction of ammonia with sulfuric acid according to the following balanced equation:

$$2\ \mathrm{NH_3$\ (g)} + \mathrm{H_2SO_4\ (aq)} \rightarrow (\mathrm{NH_4$})_2\mathrm{SO_4$\ (aq)}$$

Calculate the volume of $$\mathrm{NH_3$} (in $$liters) needed at $$20^\circ\mathrm{C}$$ and $$25.0\ \mathrm{atm} to $$react with $$150\ \mathrm{kg} of$$ $$\mathrm{H_2SO_4}.$$

Accepted Answer

$$\displaystyle 2,490\ \mathrm{L}$$

Question 3

Which of the following statements about the molar volume of a gas at STP is correct?

Accepted Answer

One mole of any ideal gas occupies $$22.4\ \mathrm{L} at$$ $$273\ \mathrm{K}$$ and $$1.00\ \mathrm{atm}.$$

Question 4

A sample of nitrogen gas ($$\mathrm{N_2$}) $$has a volume of $$11.2\ \mathrm{L} at $$STP. How many molecules are present in this sample?

Accepted Answer

$$\displaystyle 3.01 	imes 10$$^{23}$$

Question 5

Which equation should be used to calculate the volume of a gas when it is NOT at STP?

Accepted Answer

$$PV = nRT$$

Question 6

A reaction produces $$0.50\ \mathrm{mol} of $$carbon dioxide gas at STP. What volume will this gas occupy?

Accepted Answer

$$\displaystyle 11.2\ \mathrm{L}$$

Question 7

A chemical reaction produces $$3.00\ \mathrm{mol} of $$oxygen gas at $$2.00\ \mathrm{atm}$$ and $$273\ \mathrm{K}. $$What is the volume of the gas produced? ($$R = 0.0821\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$\displaystyle 24.6\ \mathrm{L}$$

Question 8

Which of the following is a correct application of the ideal gas law to determine the number of moles of a gas?

Accepted Answer

$$n = \dfrac{PV}{RT}$$

Question 9

A sample of methane gas ($$\mathrm{CH_4$}) $$occupies $$44.8\ \mathrm{L} at $$STP. What mass of methane is present in the sample? (Molar mass of $$\mathrm{CH_4$} = 16.0\ \mathrm{g/mol})$$

Accepted Answer

$$\displaystyle 32.0\ \mathrm{g}$$

Question 10

A reaction vessel contains $$5.00\ \mathrm{L} of $$hydrogen gas at $$300\ \mathrm{K}$$ and $$2.00\ \mathrm{atm}. $$How many moles of hydrogen gas are present? ($$R = 0.0821\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$\displaystyle 0.41\ \mathrm{mol}$$

Question 11

Which of the following best explains why the molar volume of a gas is useful in stoichiometric calculations at STP?

Accepted Answer

It allows direct conversion between moles of gas and volume using $$22.4\ \mathrm{L/mol}.$$

Question 12

A reaction requires $$2.00\ \mathrm{mol} of $$oxygen gas. What volume of oxygen gas is needed at STP?

Accepted Answer

$$\displaystyle 44.8\ \mathrm{L}$$

Question 13

A sample of gas has a volume of $$10.0\ \mathrm{L} at$$ $$1.00\ \mathrm{atm}$$ and $$273\ \mathrm{K}. $$How many moles of gas are present? ($$R = 0.0821\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$\displaystyle 0.446\ \mathrm{mol}$$

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