# Solutions

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**1. A sample of 6.9 moles of gas is placed in a container of volume of 30.4 L. What is the pressure of the gas in torr if the gas is at 62 ^{o}C? P = 4744 torr**

**What would be the volume of this gas if placed at STP? V = 154.6 L**

**2. A 2.1 L flask contains 4.65 g of gas at 1 atm and 27 ^{o}C, what is the density and molar mass of the gas? d = 2.21 g/L ; MW = 54.5 g/mol**

**3. A mixture of helium and neon gases is collected over water at 28 ^{o}C and 456 mmHg. If the partial pressure of He is 240 mmHg, what is the partial pressure of neon? (vapor pressure of water at 28^{o}C is 28.3 mmHg) P_{Ne} = 187.7 mmHg**

**4. A gas mixture contains three components: 28 g CO, 2.0 g H _{2} and 8.0 g of O_{2}. If the gases are at STP, what are the partial pressures of each gas? What is the total volume?**

**P**

_{CO}= 0.444 atm ; P_{H2}= 0.444 atm ; P_{O2}= 0.111 atm ; V = 50.4 L**5. Given the equation:**

** Zn _{(s)} + 2 HCl _{(aq)} -----> ZnCl_{2} _{(aq)} + H_{2(g)}**

** If 520 mL of H _{2} is collected over water at 28^{o}C and the atmospheric pressure is 1.0 atm, how many g of Zn was used at the start of the reaction? (vapor pressure of water at 28^{o}C is 28.3 mmHg). 1.33 g Zn**

**6. A sample of 2.0 moles of hydrogen gas is placed in a container with a volume of 10.4 L. What is the pressure of the gas in torr if the gas is at 25 ^{o}C? P = 3572 torr**

**7. A 2.4 L sample of gas is placed in a container at 25 ^{o}C and 2 atm of pressure. If the temperature is raised to 50^{o}C and the volume is changed to 5.6 L, what is the new pressure? P = 0.929 atm**

**8. A gas is placed in a balloon with a volume of 3.0 L at 35 ^{o}C and 800 torr. What would be the new volume for the gas if placed under STP? V = 2.8 L**

**9. How many moles of gas would occupy a volume of 22.4 L at a pressure of 745 torr and a temperature of 26 ^{o}C? n = 0.894 mol**

**10. Calculate the volume of 10.8 g of CO _{2} at STP. V = 5.5 L**

**11. Calculate the volume of 0.681 g of N _{2} at STP. V = 0.55 L**

**12. A gas at 772 mmHg and 35 ^{o}C occupies a volume of 6.85 L, calculate its volume if the temperature is raised to 50^{o}C at a constant pressure. V = 7.18 L**

**13. Drano uses a mixture of sodium hydroxide and aluminum powder to generate hydrogen gas and heat when placed in a drain. Calculate the volume of H _{2} produced at STP if 3.12 g of Al is used. (Mole ratio is 3 H_{2} to 2 Al). V = 3.88 L**

**14. A piece of sodium metal undergoes complete reaction with water as follows:**

** 2 Na _{(s)} + 2 H_{2}O _{(l)} -------> 2 NaOH _{(aq)} + H_{2(g)}**

** The hydrogen gas is collected over water at 25 ^{o}C. The volume of gas is 246 mL measured at 1 atm. Calculate the number of grams of Na used in the reaction. (vapor pressure of water = 0.0313 atm) 0.448 g Na**