C6 The rate and extent of chemical change Flashcards Preview

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Flashcards in C6 The rate and extent of chemical change Deck (45)
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1

How can the rate of a chemical reaction can be found.

It can be found by measuring the quantity of a reactant used over time (divided by time taken to change) or the quantity of product formed over time (divided by time taken to change)

2

Write an equation for the rate of a chemical reaction.

mean rate of reaction = quantity of reactant used/

time taken

3

What two units can be used for the rate of a reaction. Explain what each symbol stands for.

The units of rate of reaction may be given as g/s or cm3/s.

g = grams

s = time in seconds

cm3 = volume in centimeters cubed

 

 

 

4

For the Higher Tier, students only.

 How can you express rate in terms of moles.

 The units for rate of reaction in terms of moles is  mol/s.

5

What Factors  affect the rate of chemical reactions.

Factors which affect the rates of chemical reactions include: the concentrations of reactants in solution, the pressure of reacting gases, the surface area of solid reactants, the temperature and the presence of catalysts.

6

In what way does temperature affect the rate of a chemical reaction.

Increasing the temperature increases the frequency of collisions and make the collisions more energetic, and so increases the rate of reaction.

7

Explain how changing the concentration of reactants the pressure of reacting gases and the surface area of solids affects the rate of a chemical reaction.

Increasing the concentration of reactants in solution, the pressure of reacting gases, and the surface area of solid reactants increases the frequency of collisions and so increases the rate of reaction.

8

Explain what is meant by surface area.

The area of a surface which is exposed.

9

Give an example where a reaction is faster when the surface area is increased.

A specific mass of calcium carbonate ( marble chips). reacts with hydrochloric acid at a much slower rate than the same mass of marble chips which has been crushed into a powder.

10

How would you measure the rate of the reaction between Zinc and HCl.

Measure the volume of gas collected every 20 seconds in a gas syringe.

11

How would you measure the rate of the reaction between sodium thiosulphate  and HCl.

Place HCl into a conical flask, place a cross underneath  the flask add the Sodium thiosulphate and start the clock. Record the time it takes for the cross to no longer be visable, repeat this for each variable.

12

What is minimum activation energy.

It is the minimu amount of energy that particles must posses when they collide for a reaction to happen.

13

Explain why a gate made from Iron spindles rusts faster then a gate made from soild iron.

The spindles have more surface area.

14

What are catalysts ?

Catalysts change the rate of chemical reactions but are not used up during the reaction. Different reactions need different catalysts.

Enzymes act as catalysts in biological systems.

15

What are enzymes ?

Enzymes act as catalysts in biological systems.

16

Give an example of an enzyme ?

Amylase is an enzyme that breaks down starch into glucose

17

How do catalysts work ?

Catalysts increase the rate of reaction by providing a different pathway for the reaction that has a lower activation energy.

18

How can a  reaction profile for a catalysed reaction can be drawn in the following form:

19

What are reversible reactions.

In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called

reversible reactions.

20

How can a reversible reaction be represented ?

The reversible sign is the last equation on the card.

21

If a reversible reaction is exothermic in one direction, it is ............................. in the opposite direction.

If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction.

22

Exothermic reactions............................heat

Give out

23

Endo thermic reactions......................................... Heat

Take in heat.

24

An exothermic reaction is represented by.........?

 an negative  sign in front of the delta H

 

25

An endothermic reaction is represented by.........?

Put a positive sign in front of the delta H

26

If you increase the temperature for an exothermic reaction which way will the reaction speed up ?

The backward reaction will speed up..

27

If you increase the temperature for an endothermic reaction which way will the reaction speed up ?

The forward reaction will speed up.

28

If you increase the temperature for an exothermic reaction how will it affect the yield of product. ?

 The product yield decreases.

29

If you increase the temperature for an endothermic reaction which way will the reaction speed up ?

The product will increase.

30