Rates of Reaction

Question 1

Measuring the rate of a reaction

Answer 1

Amount of reactant used up
———————
Time taken

Amount of product obtained
———————
Time taken

Question 2

Collision theory

Answer 2

Chemical reactions can only take place when the reacting particles collide with each other. The collisions must have sufficient energy.

Question 3

Effect of surface area on rate of reaction

Answer 3

Increasing the surface area to volume ratio, increases the rate of the reaction (There is more surface for collisions to occur, so they occur more often)

Question 4

Effect of concentration on rate of reaction

Answer 4

Increasing the concentration of solutions increases the rate of reaction (There are more reacting particles so collisions occur more often)

Question 5

Effect of temperature on rate of reaction

Answer 5

Increasing the temperature increases the rate of reaction (the reactants have more kinetic energy so speed up, therefore collide more often)

Question 6

Activation energy

Answer 6

The minimum amount of energy needed for a reaction to occur

Question 7

Surface area & rate of reaction (core practical)

Answer 7

Aim: Investigate how the surface area of the calcium carbonate (marble chips) affects the rate
Measuring: the volume of carbon dioxide produced
Method: Measure 40cm^3 of HCl into a conical flask. Add 5g of small marble chips to the flask. Stopper the flask and start the stopwatch. Record the volume of gas produced after every 30 seconds until the reaction has finished. Repeat using 5g of larger marble chips.

Question 8

Temperature & rate of reaction (core practical)

Answer 8

Aim: Investigate the effect of temperature on the rate of reaction between sodium thiosulfate and hydrochloride acid
Measuring : The time it takes for colour change
Method: Put 50cm^3 of sodium thiosulfate solution into a 300cm^3 conical flask. measure out 5cm^3 of HCl in a test tube. Clamp the conical flask in place in a water bath at a certain temperature and place the test tube in the same bath. Record the temperature. After 5 minutes remove the flask and place it on a piece of paper marked with a cross. Add the acid to the thiosulfate and start the stop watch. Stop the time when the cross disappears from above. Note the time and take the final temperature of the mixture. Repeat a couple times with other temperatures.

Question 9

Catalysts

Answer 9

Substances that speed up reactions without altering the products of a reaction

Question 10

Exothermic

Answer 10

Energy is transferred to the surroundings

Question 11

Endothermic

Answer 11

Energy is taken from the surroundings