C5- Chemical Changes

Question 1

What do 2 reactants from metal oxide?

What type of reaction is this?

Answer 1

1) Metals react with oxygen to produce metal oxides.

2) The reactions are oxidation reactions because the metals gain oxygen.

Question 2

What happens to metal atoms when metals react with other substances?
What is the reactivity of a metal related to?

Answer 2

1) Metal atoms form positive ions.

2) The reactivity of a metal is related to its tendency to form positive ions.

Question 3

Name the reactivity series in order.

Answer 3

1) Potassium
2) Sodium
3) Lithium
4) Calcium
5) Magnesium
6) Aluminium
7) Zinc
8) Iron
9) Tin
10) Lead
11) Copper
12) Silver
13) Gold

Question 4

Explain the reactivity between water and the elements in the reactivity series.

Answer 4

1) Potassium, Sodium, Lithium and Calcium- fizz, giving off hydrogen gas and leaving an alkaline solution of metal hydroxide.
2) Magnesium, Aluminium, Zinc and Iron- very slow reaction.
3) Tin and Lead- slight reaction with steam.
4) Copper, Silver and Gold- no reaction, even with no steam.

Question 5

Explain the reactivity between dilute acid and the elements in the reactivity series.

Answer 5

1) Potassium, Sodium, Lithium and Calcium- Explodes.
2) Magnesium, Aluminium, Zinc and Iron- Fizz, giving off hydrogen has and forming a salt.
3) Tin and lead- React slowly with warm acid.
4) Copper, Silver and Gold- No reaction

Question 6

When is Hydrogen gas given off?

Answer 6

1) Hydrogen gas is given off if metals react with water or dilute acids. The gas ‘pops’ with a lighted spill.

Question 7

What is oxidation?

What is reduction?

Answer 7

1) Oxidation is the loss of electrons.

2) Reduction is the gain of electrons.

Question 8

What is the rule about metals displacing eachother?

Answer 8

1) A more reactive metal will displace a less reactive metal from an aqueous solution of one of its salts.

Question 9

What does a metal ore contain enough of?

Answer 9

1) A metal ore contains enough of the metal to make it economic to extract the metal.

Question 10

What types of metals are found in the earth?

Answer 10

1) Unreactive metals are such a gold are found in the earth as the mettal itself.
2) Most metals are found as compounds that require chemical reactions to extract the metal.

Question 11

How can metals less recative than carbon be extracted?

Answer 11

1) Metals less reactive than carbon can be extracted from their oxides by reduction using carbon

Question 12

What is a salt?

How can salts be made?

Answer 12

1) A salt is a compound formed when the hydrogen in an acid is wholly or partially replaced by metal or ammonium ions.
2) Salts can be made by reacting a suitble metal with an acid. The metal must be above hydrogen in the reactivity series but not very reactive.

Question 13

What type of reaction is the reaction between a metal and an acid. Why is this?

Answer 13

1) The reaction between a metal and an acid is an example of a redox reaction. The metal ions are oxidised and hydrogen ions from the acid are reduced.

Question 14

What are acids neutralised by and what does this produce?

Answer 14

1) Acids are neutralised by alkalis (eg soluble metal hydroxides) and bases (eg insoluble metal hydroxides and metal oxides) to produce salts and water.

Question 15

What does the particular salt produced in a reaction depend on?

Answer 15

1) The acid used (hydrochloric acid produces chlorides. Nitric acid produces nitrates. Sulfuric acid produces sulfates)
2) The positive ions in the base, alkali or carbonate .

Question 16

How can soluble salts be made?

Answer 16

1) Soluble salt can be made from acids by reacting them with solid insoluble substances such as metals, metal oxides, hydroxides or carbonates.
2) The solid is added to the acid until no more reacts and the excess solid is filtered off to roduce a solution of the salt.

Question 17

When is an indicator needed?

Answer 17

1) An indicator might be needed when a soluble salt is prepared reacting an alkali with an acid.

Question 18

What does a carbonate produce when it reacts with an acid?

Answer 18

1) A carbonate reacts with an acid to produce a salt, water and carbon dioxide.

Question 19

Explain what acids are.

Explain what a base is.

Answer 19

1) Acids are substances that produce H+ ions when added to water.
2) A base is a substance that will neutralise an acid.

Question 20

What is an alkali?

Answer 20

1) An alkali is a soluble hydroxide. They produce OH- ions when added to water.

Question 21

Explain in regards to pH values how you can work out if something is acidic or an alkali?

Answer 21

1) Solutions with pH values less than 7 are acidic. Solutions with pH values more than 7 are alkaline. A solution with a pH value of 7 is neutral.