Chemistry-C2-2b

Question 1

What are the four factors that affect the rate of reaction?

Answer 1

• Temperature
• Concentration
• Catalyst
• Surface area and solids

Question 2

Describe three different ways of measuring the rate of a reaction.

Answer 2

• How much precipitation forms
• Change in mass (usually a gas given off)
• The volume of gas given off

Question 3

Explain how higher temperature, higher concentration and larger surface area increases the successful collision between particles.

Answer 3

Higher temperature-When the temperature is increased the particles all move quicker. If they’re moving quicker, they’re going to collide more often.
Higher concentration-If a solution is more concentrated it means there are more particles of reactant knocking about between the water molecules which makes collisions between the important particles more likely. In a gas, increasing the pressure means the particles are more squashed up together so there will be more frequent collisions.
Larger surface area-If one of the reactants is solid then breaking it up into smaller pieces will increase the total surface area. This means the particles around it in the solution will have more area to work on, so there’ll be more frequent collisions.

Question 4

What is activation energy?

Answer 4

Activation energy is the minimum amount of energy needed by the particles to react.

Question 5

What is the definition of a catalyst?

Answer 5

A catalyst is a substance which speeds up a reaction, without being changed or used in the reaction.

Question 6

Discuss the advantages and disadvantages of using catalysts in industrial processes.

Answer 6

Advantages:

• Catalysts increase the rate of reaction, which saves a lot of money simply because the plant doesn’t need to operate for as long to produce the same amount of stuff.
• A catalyst will allow the reaction to work at a much lower temperature. That reduces the energy used up in the reaction,which is good for sustainable development and can save a lot of money too.

Disadvantages:

• They can be very expensive to buy, and often need to be removed from the product and cleaned. They never get used up in the reaction though, so once you’ve got them you can use them over and over again.
• Different reactions use different catalysts, so if you make more than one product at your plant, you’ll probably need to buy different catalysts for them.
• Catalysts can be ‘poisoned’ by impurities, so they stop working, e.g. sulphur impurities can poison the iron catalyst used in the Haber process (used to make ammonia and fertilisers). That means you have to keep your reaction mixture very clean.

Question 7

What is an exothermic reaction?

Answer 7

An exothermic reaction is one which transfers energy to the surroundings, usually in the form of heat and usually shown by a rise in temperature.

Question 8

Give three examples of of exothermic reactions.

Answer 8

• Burning fuels (combustion)
• Neutralisation reactions
• Oxidation reactions

Question 9

The reaction to split ammonium chloride into ammonia and hydrogen chloride is endothermic. What can you say for certain about the reverse reactions?

Answer 9

The reaction can be Exothermic and Endothermic.

Question 10

What does the pH scale show?

Answer 10

The pH scale shows whether a substance is as acid or an alkali or a neutral substance. It also shows its strength.

Question 11

What type of ions are always present in acids?

Answer 11

H+ ions

Question 12

What type of ions are always present in alkalis?

Answer 12

OH- ions

Question 13

What is neutralisation?

Answer 13

The reaction between acids and bases is called neutralisation:
Acid+Base=Salt+Water

Question 14

Write down the general equation for neutralisation in terms of ions.

Answer 14

H+ + OH- = H2O

Question 15

Write down the state symbol that means ‘dissolved in water’.

Answer 15

Aq

Question 16

What is the general equation for reacting an acid with a metal?

Answer 16

Acid+Metal=Salt+Hydrogen

Question 17

Name a metal that doesn’t react at all with dilute acids.

Answer 17

Copper

Question 18

What type of salts do hydrochloric acid and sulfuric acid produce?

Answer 18

Hydrochloric acid always produces ‘chloride’ salts.

Sulphuric acid always produces ‘sulfate’ salts.

Question 19

What type of reaction is
'acid + metal oxide'
and
'acid + metal hydroxide'
?

Answer 19

Neutralisation reactions.

Question 20

Give a practical use of precipitation reactions.

Answer 20

Precipitation reactions can be used to remove poisonous ions from drinking water.

Question 21

What is electrolysis?

Answer 21

Electrolysis is the process of splitting up with electricity.

Question 22

Explain why only liquids can be electrolysed.

Answer 22

Because they need free ions which are only found in liquids

Question 23

Give one industrial use of sodium hydroxide and two uses of chlorine.

Answer 23

Sodium hydroxide:
-Used to make soap
Chlorine:
-Used to make bleach
-Used to make plastics

Question 24

Give two different uses of electroplating.

Answer 24

Decoration:
-silver is attractive, but very expensive. It’s much cheaper to plate a boring brass cup with silver than it is to make the cup out of solid silver.
Conduction:
-Metals like copper conduct electricity well. Because of this they’re often used to plate metals for electronic circuits and computers.