Ideal gases: Grade 11 Past Paper Questions

1.4 Which ONE of the following pairs represents the CONJUGATE ACID and CONJUGATE BASE of HPO₄²⁻? A. PO₄³⁻ and HPO₄²⁻ B. HPO₄²⁻ and H₃PO₄ C. H₂PO₄⁻ and PO₄³⁻ D. HPO₄²⁻ and PO₄³⁻. 1.5 Which ONE of the following processes is exothermic? A. Melting ice cubes. B. Baking bread. C. Burning a candle. D. Photosynthesis. 1.6 Which ONE of the following is correct for Boyle's Law? A. P ∝ 1/V when temperature is constant. B. P ∝ V when temperature is constant. C. P ∝ 1/T when volume is constant. D. P ∝ T when volume is constant. 1.7 Which ONE of the following graphs represents the deviation of real gas behaviour (broken line) from ideal gas behaviour (solid line)?

4.3 A solution is formed by adding 30 cm³ of HCl of concentration 0,15 mol·dm⁻³ to 20 cm³ of Ca(OH)₂ of concentration 0,1 mol·dm⁻³, according to the following balanced equation: Ca(OH)₂ + 2HCl → CaCl₂ + 2H₂O. Determine the final pH of the solution. QUESTION 5. 5.1 A gas is contained in Chamber A, which has a volume of 5,3 dm³, and is sealed off from Chamber B, which has a volume of 3,2 dm³. Initially, only Chamber A contains gas at a pressure of 135,2 kPa, while Chamber B is a vacuum (contains no gas). The chambers are then connected by opening a valve between them, and the gas is allowed to expand freely. The temperature remains constant and no gas escapes. 5.1.1 State Boyle's Law in words. 5.1.2 Explain, in terms of Boyle's Law, what happens to the pressure of the gas after the valve is opened. 5.1.3 Calculate the final pressure of the gas after the valve is opened. 5.2 Sketch a graph that shows the relationship between pressure (y-axis) and volume (x-axis) for a fixed amount of gas at constant temperature. 5.3 State the conditions of temperature and pressure under which a real gas behaves as an ideal gas. 5.4 Which real gas behaves the closest to an ideal gas? Explain the answer.