Question

Question 37 - Part A Which of the following compounds will behave least like an ideal ges at low temperatures? O CCH 0 0 OKr OF o Ar SUDAN Request Answer Part B According to the kinetic molecular theory, the pressure of a gas in a container will decrease the the average kinetic energy of gas particles increases number of collisions with the container wall increases O temperature of the gas decreases O volume of the container decreases number of moles of the gas increases Submit Request Answer Part Which of the following gases has the highest average speed at 400K? OCH Осо, O NO O SF OUF Submit Request Answer Part D An unknown gas efuses 1.73 times faster than krypton. What is the molar mass of the gas? 110 g/mol 16.0 g/mel 28.0 g/mol 251 g/mol 48.4 g/mol Submit Request Answer Part E Which statement about real gases is true? The volume of the gas particles is 2010 The mass of the gas particles is zero The behavior of real gases can be exactly predicted using the ideal gas law Forces of attraction and repulsion exist between gas particles at close range Submit Request Answer

Answer 1

Part A

CCl4 - This is because CCl4 has a dipole moment whereas others do not. A molecule with dipole moment will have some interactions with the neighboring molecules. Thus it deviates largely from ideal behavior.

Part B

Temperature of the gas decreases

Explanation :

Gay_Lussac's law gives the relationship between temperature and pressure

P ~ T

Thus decrease in T causes a decrease in P.

Why other options are wrong?

• When avg KE increases, the T increases, which causes an increase in P.
• When no. of collisions with the wall increases the pressure increases.
• When V of container decreases, due to Boyle's law relationship ie. P ~ 1/V, we see an increase in pressure.
• When number of moles of gas increases P increases, from the gas law - PV = nRT

Part C

CH4

Average Speed = √(3 RT / m)

Thus avg speed is inversely proportional to molar mass. Therefore CH4 with lowest molar mass has the highest avg speed.

Part D

28

Graham's law of effusion states that effusion of gas is inversely proportional to sqrt of mass of it's particles.

Rate1 / Rate 2 = √(M2/M1)

Let particle 1 be Kr with molar mass 85. Therefore,

Rate 1 / Rate 2 = 1/1.73 = √(M2/85)

ie. 0.578 = √(M2/85)

ie. (0.578)^2 = M2/85

Therefore, M2 = 85 * (0.578)^2

= 28.4 ~ 28

Part E

Forces of attraction and repulsion exists between the gas particles at close range.

Volume and mass can't be zero, be it ideal or real. If it follows ideal gas law then it is called ideal gas and not real gas. Thus only the last option is right.