Question

Lab work:

empty flask mass: 88.00 grams

2.00 atm pressure added

mass: 88.358 g

mass of air: .358 g

pressure: 2 atm

Question 1: How many moles of air were in the Erlenmeyer flask when the total air pressure was 2.00 atm?

A. 0.179 mol

B. 0.0155mol

C. 0.0124mol

D. 0.00620mol

Question 2: Given the data you collected when adding 2.00 atm of air to the Erlenmeyer flask, what is the molar mass of air?

A. 17.9g/mol

B. 35.8g/mol

C. 12.4g/mol

D. 28.9g/mol

Question 3: The principal components in air are oxygen, nitrogen, argon, and carbon dioxide. Air is overwhelmingly composed of one of these elements. Based on the molar mass of each of these compounds, which one has the molar mass most similar to air?

A. Nitrogen

B. Oxygen

C. Carbon dioxide

D. Argon

Answer 1

Given data:

Mass of empty flask = 88 g.

Pressure added to the flask = 2 atm.

Now, the mass of flask = 88.358 g

i.e. The mass of air = 0.358 g.

1. No. of moles of air in the Erlenmeyer flask when the total air pressure was 2.00 atm. = 0.358/29, i.e. 0.0124

Therefore, the answer is option C.

2. The molar mass of air = 28.9, option D.

Explanation: The main composition of air = 78% of nitrogen + 22% of oxygen

Therefore, the molar mass of air = 0.78*28 + .22*32, i.e. 28.9.

3. The answer is option A, nitrogen, molar mass = 28.0 g/mol.