Question

The molar mass of two equally sized samples of unknown gaseous compounds is shown in the table. Molar Mass Comparison Gas Molar Mass A 4.00 g/mol B 2.01 g/mol Which statement describes the density and effusion of both gases at STP? Gas A has a higher density and effuses faster than Gas B. Gas A has a higher density and effuses slower than Gas B. Gas A has a lower density and effuses faster than Gas B. Gas A has a lower density and effuses slower than Gas B.

Answer 1

Answer: B. Gas A has a higher density and effuses slower than Gas B

Explanation: To calculate the rate of effusion of gas, we use Graham's Law.

This law states that the rate of effusion of gas is inversely proportional to the square root of the molar mass of the gas. The equation given by this law follows:

$\text{Rate of effusion}\propto \frac{1}{\sqrt{\text{Molar mass of the gas}}}$

For the rate of effusion of A to B, we write the expression:

$\frac{Rate_{A}}{Rate_{B}}=\sqrt{\frac{2.01}{4.0}$

$Rate_{A}=0.70Rate_{B}$

Thus Gas B would diffuse faster than gas A.

As the two gases are equally sized, the y have same volume but Gas A has higher mass. Thus Gas A would be more dense than Gas B.

$Density=\frac{mass}{volume}$

Answer 2

Effusion  is the process of a gas being poured out through a hole diametrically smaller than the structural exit of the container.

A lighter gas effuses faster than a heavier gas.

Thus gas A has a lower density and effuses slower than Gas B.