States of Matter: Gas

Choose the INCORRECT statement about the assumptions of the kinetic molecular theory.

• The collision between gas molecules is elastic.

• The volume of gas is negligible compared to the volume of container.

• At constant temperature, each molecule has the same velocity.

• Gas molecules move randomly and continuously.

“At constant temperature and pressure the volume of a gas is directly proportional to the number of moles of the gas”

The law describes the above statement is

• Charles’ law

• Avogadro’s law

• Boyle’s law

• Ideal Gas law

Gas behaves almost ideally at very low pressure. As the pressure is lower.

• The gas molecules are far apart from each other.

• Intermolecular forces become weaker.

• Volume of the gas decreases.

• It obeys kinetic molecular theory.

Which of the following is NOT TRUE?

• Viscosity increases as temperature increases.

• Viscosity arises because of cohesive forces within the liquid molecules.

• Viscosity increase with stronger intermolecular forces.

• Liquid with low viscosity can flow freely.

The following factors affecting the vapour pressure of a liquid EXCEPT

• volume of liquid.

• temperature.

• molecular size of liquid.

• relative molecular mass of liquid.

According to Boyle’s Law, the relationship between pressure and volume of a fixed amount of gas at constant temperature is:

• Directly proportional

• Inversely proportional

• Remains constant regardless of changes

• Independent of each other

When plotting the graph of V vs T (in °C) for a fixed amount of gas at constant pressure, the line intercepts the x-axis at –273 °C. What does this suggest?

• Gas molecules stop moving completely at 0 °C.

• Pressure of the gas becomes zero at room temperature.

• Volume of a gas theoretically becomes zero at absolute zero.

• Real gases cannot exist above –273 °C.

Two identical flasks at the same temperature and pressure are filled separately with 2 g of hydrogen (H₂) and 32 g of oxygen (O₂). Which statement best explains why the pressure inside both flasks is the same?

• As both samples are kept at constant volume, any change in pressure is prevented according to Boyle’s Law.

• The lighter hydrogen molecules move faster than oxygen molecules, but their higher velocity balances the lower molecular mass, producing the same pressure. (Kinetic Molecular Theory)

• Both flasks contain the same amount of molecules, because each sample is 1 mol of gas. (Avogadro’s Law)

• Because temperature is the same, the gases expand equally and thus exert the same pressure, as explained by Charles’s Law.