energetics

Question 1

What is an exothermic reaction?

Answer 1

One where energy is given out to surroundings, usually shown by rise in temperature

Question 2

What is an endothermic reaction?

Answer 2

One where energy is taken in from surroundings, usually shown by fall in temperature

Question 3

Is bond-breaking exothermic or endothermic?

Answer 3

Breaking is endothermic (B-END)

Question 4

Is bond-making exothermic or endothermic?

Answer 4

Making is exothermic (M-EX)

Question 5

What is enthalpy change?

Answer 5

The overall change in energy in a reaction

Question 6

What are the units for enthalpy change?

Answer 6

Kilojoules per mole - kj/mol

Question 7

Is enthalpy change positive or negative for exothermic reaction?

Answer 7

Negative (N-EX)

Question 8

Is enthalpy change positive or negative for endothermic reaction?

Answer 8

Positive (P-END)

Question 9

What is activation energy?

Answer 9

Minimum energy needed for the reaction to occur. Shown by initial rise in the line on energy diagram - represents energy needed to break the old bonds

Question 10

How does a catalyst speed up the reaction?

Answer 10

Provides an alternative reaction pathway with a lower activation energy

Question 11

Do products in exothermic reaction have higher or lower energy than reactants?

Answer 11

Lower - energy is given out to surroundings (enthalpy change is negative)

Question 12

Do products in endothermic reaction have higher or lower energy than reactants?

Answer 12

Higher - they take in heat during the reaction (enthalpy change is positive)

Question 13

Describe an experiment to measure enthalpy change of neutralisation reaction

Answer 13

1. Take temperature of reagents (acid and alkali) 2. Mix in polystyrene cup, using lid and insulation to reduce energy loss to surroundings. 3. Take temperature of solution at end of reaction.