1. A cylinder of Xenon has a volume of 750. ml. At 25.0°C the cylinder has a pressure of 655 torr. How much Argon is present in the cylinder?


a. 240. moles

b. 0.0264 moles

c. .315 moles

d. 26.5 moles

2.If a 25 liter cylinder of gaseous ammonia at atmospheric pressure (1.0 atm) is heated from 50°C to 450°C, what is the final pressure?


a. 9.0 atm

b. 0.11 atm

c. 0.45 atm

d. 2.2 atm

3.What are the relative rates of effusion of molecular hydrogen and molecular oxygen?

a. 2

b. 0.5

c. 4

d. 1

4.An unknown gas has a molecular weight of 30.07 g/mol. What is the density of the gas at STP?

a. 1.3 x 10-3 g/cm3

b. .0385 g/cm3

c. 1.5 g/cm3

d. 3.1 x 10-4 g/cm3

a. Use pV = nRT and solve for n= number of moles.

Then moles = g/molar mass. Solve for grams.

To solve these questions, we'll go step by step and explain how to get the answers:

1. To find the amount of Argon in the cylinder, we need to use the Ideal Gas Law equation: PV = nRT. First, we convert the volume from milliliters to liters by dividing by 1000: 750 ml = 0.75 L. Now, rearranging the equation to solve for moles (n), we have n = PV / RT. Plugging in the values, P = 655 torr (convert to atm by dividing by 760), V = 0.75 L, R is the ideal gas constant (0.0821 L·atm/(mol·K)), and T is the temperature in Kelvin (25 °C = 298 K). Calculate moles (n) using these values. The resulting answer will be in moles of Xenon. However, the question asks for Argon, so we need to convert moles of Xenon to moles of Argon using the molar mass ratio of Argon to Xenon (39.95 g/mol / 131.29 g/mol). Calculate the moles of Argon.

2. To find the final pressure of the cylinder, we need to use the combined gas law equation: P1V1/T1 = P2V2/T2. Given that P1 = 1 atm, V1 = 25 L, T1 = 50 °C (convert to Kelvin by adding 273), and T2 = 450 °C (convert to Kelvin as well), we can solve for P2. Plug in the known values and calculate the final pressure.

3. The relative rates of effusion of two gases can be determined by comparing their molar masses. The rate of effusion is inversely proportional to the square root of molar mass. Since molecular hydrogen (H2) has a molar mass of 2 g/mol and molecular oxygen (O2) has a molar mass of 32 g/mol, we can calculate the ratio of their rates of effusion by taking the square root of their molar mass ratio: sqrt(molar mass of H2 / molar mass of O2). Calculate the relative rates of effusion.

4. To find the density of the gas at STP, we need to use the Ideal Gas Law: PV = nRT. Rearrange the equation to solve for density (d), which is mass (m) divided by volume (V). Since density = m/V, we can rewrite the equation as m/V = (P/RT) * M, where M is the molar mass of the gas. At STP, the pressure (P) is 1 atm, the temperature (T) is 273 K, and the molar mass (M) of the unknown gas is given as 30.07 g/mol. Calculate the density (d) using the known values for pressure (P), temperature (T), and molar mass (M).

By following these steps, we'll be able to determine the correct answers for each question.