Rates of reaction — final check

1. determine / calculate / explain

Calcium granules react with water, and the hydrogen is collected in a gas syringe. The table shows the results. (a) Determine the total volume of hydrogen made. (b) Calculate the average rate over the first 10 s. (c) Determine the time at which the reaction stopped. Explain how you can tell.

(a) Total volume: ______________ unit ________

(b) Rate over the first 10 s: ______________ unit ________

(c) Time the reaction stopped: ______________ unit ________

(c) How you can tell.

2. state / describe / explain / give

A pupil wants to follow the rate of the reaction between copper(II) carbonate powder and dilute sulfuric acid by the loss of mass. (a) State the apparatus she needs. (b) Describe what she measures, and when. (c) Explain why she puts cotton wool in the neck of the flask. (d) Supplement. Give one advantage of this method over collecting the gas in a gas syringe.

(a) Apparatus

(b) What and when

(c) The cotton wool

(d) Supplement: an advantage

3. predict / identify

Aluminium foil reacts with dilute hydrochloric acid. Predict whether each change makes the reaction faster or slower, and identify the factor that changes. (a) The same mass of aluminium powder is used. (b) The acid is cooled from 30 °C to 15 °C. (c) The acid is mixed with an equal volume of water first. (d) In a different reaction, two gases react in a sealed syringe. The plunger is pushed in at the same temperature, so the gas mixture fills half the volume.

(a) Powder

(b) Cooler acid

(c) Water added

(d) Plunger pushed in

4. identify

Hydrogen peroxide breaks down very slowly into water and oxygen. A pupil adds 1.00 g of black copper(II) oxide powder, and oxygen comes off much faster. Which results would show that copper(II) oxide is a catalyst for this reaction? Select all that are correct.

Tick every correct statement.

• The solution turns blue as the powder is used
• Collecting 50 cm³ of oxygen takes 40 s with the powder and 300 s without
• More oxygen is made in total with the powder
• The powder is still black at the end
• The powder filtered off and dried at the end has a mass of 1.00 g

5. explain

Supplement. Magnesium ribbon reacts with dilute hydrochloric acid. (a) Explain, using collision theory, why the reaction is faster with more concentrated acid. (b) The reaction gets slower as it goes on. Explain why.

(a) More concentrated

(b) Slowing down

6. identify

Supplement. Which change speeds up a reaction by making a larger share of the collisions successful, without making the particles collide more often?

Circle one answer.

• Adding a catalyst
• Raising the pressure of the gases
• Using more concentrated acid
• Using a powder