C3

Question 1

What is the conservation of mass?

Answer 1

No atoms are lost or made during a reaction so the mass of the product equals the mass of reactants.

Question 2

What could be a possibly reason for the products to appear to have changed in mass?

Answer 2

Gas in the air could have reacted with the reactants to form products which would make the mass of products seem to increase

Gas formed as a product of a reaction could have escaped from the reaction vessel so the mass of products would appear to decrease.

Question 3

Ar=

Isotopes

Answer 3

(Mass of first isotope x percentage of first isotope)+(mass of second isotope x percentage of second isotope) / 100

Question 4

Name these ions

1) sulphate ion
2) hydroxide ion
3) nitrate ion
4) carbonate ion
5) ammonium ion
6) phosphate ion

Answer 4

1) (SO4)2-
2) ( OH)-
3) (NO3) -
4) (CO3) 2-
5) (NH4)+
6) (Pr4) 3-

Question 5

What is a half equation ?

Answer 5

A half equation shows how electrons are transferred in oxidation and reduction reaction

Question 6

What is an ionic equation ?

Answer 6

An ionic equation is an equation for any reaction involving ions that happens in solution where only the reacting particles and the products formed are included

Question 7

What is the mass of one mole of any atoms

Answer 7

the mass of 1 mole of atoms is equal to its relative formula mass

Question 8

Moles=

Answer 8

Moles= Mass/Mr

Question 9

Definition an exothermic reaction

Answer 9

An exothermic reaction gives out energy to the temperature of the surroundings increase

Question 10

Definition of an endothermic reaction

Answer 10

An exothermic reaction takes in energy so the temperature of the surroundings fall

Question 11

What is a reaction profile?

Answer 11

A reaction profile shows what type of reaction cheers the products are low energy in the reactants energy is released so it is exothermic if the products are a higher energy than the reactants energy is absorbed so it is endothermic

Question 12

Definition of activation energy

Answer 12

activation energy is the minimum energy for bonds to break and a reaction to start. It is the energy difference between the reactants and the tip of the curve

Question 13

Is bonds breaking exothermic or endothermic?

Answer 13

When bonds break they need to absorb energy so it is endothermic

Question 14

Is bonds forming exothermic or endothermic?

Answer 14

When bonds form they release energy so this is exothermic

Question 15

Overall energy change=

Answer 15

Overall energy change= energy to break bonds- energy released to form bonds
(Positive energy change=endothermic)
(Negative energy change = exothermic)

Question 16

Definition of an acid

Answer 16

an acid has a pH of seven or less and forms H + ions in water

Question 17

Definition of a base

Answer 17

base has a pH of seven or more

Question 18

Definition of an alkali

Answer 18

and alkali is a base that dissolves in water to form a hydroxide ion

Question 19

What happens as pH increases?

Answer 19

, as pH increases the hydrogen ions decrease

Question 20

What happens when an acid reacts with a base ?

Answer 20

When an Acid reacts with a base neutralisation occurs which forms a salt and water

Question 21

What are titrations used for ?

Answer 21

Titrations are used to see how much acid is needed to neutralise a base

Question 22

What do neutralisation curves show?

Answer 22

Neutralisation curves show when neutralisation happens

Question 23

What does acid strength tell you?

Answer 23

An acids strength tells you how many molecules ionise in water

Question 24

What does the concentration of an acid tell you?

Answer 24

The concentration tells you how much acid is in a litre of water

Question 25

By how much must the concentration increase to decrease the pH by one?

Answer 25

The concentration must increase 10 times to decrease the pH by one.

Question 26

Acid + metal—>

Answer 26

Acid + metal —> salt + hydrogen

Question 27

Acid + metal carbonate —>

Answer 27

Acid + metal carbonate —> salt + water + carbon dioxide

Question 28

Acid + alkali —>

Answer 28

Acid + alkali —> salt + water

Question 29

How can we make Soluble salts in the lab ?

Answer 29

1) as an acid and a metal or insoluble base which will react to produce a soluble salt and water . When the acid has been neutralised the excess solid will sink to the bottom of the flask 2) filter off the access solids to get the solution containing only salt and water 3) heating solution gently to slowly evaporate off some of the water 4) leave the solution to cool and allow salt to crystallize 5) filter off the solid and leave it to dry

Question 30

How can we make an insoluble salt in the lab?

Answer 30

Using a precipitation reaction 1) pick two right soluble salts 2) Add a spatula of each soluble salt in separate test tubes and add deionised water to dissolve them 3) Tip the two solutions into a small beaker and give a good stir 4) filter out the insoluble salt 5) leave it to dry

Question 31

What is a redox reaction ?

Answer 31

A redox reaction is a reaction which includes the transferring of electrons

Question 32

What is oxidation ?

Answer 32

Oxidation is either the loss of electrons in the gain of oxygen

Question 33

What is reduction?

Answer 33

Reduction in either the gain of electrons or the loss of oxygen

Question 34

What is electrolysis ? How does it work?

Answer 34

Electrolysis is the breakdown substances using electricity , 1) a current passes through an electrolyte (ionic compound) causing it to decompose 2) the positive ions moved to the cathode and reduced , the negative ions move towards the anode and are oxidised 3) when the aunts gain/lose electrons they formed uncharged substances and are discharged from the solution

Question 35

How can you determine which elements are oxidized and which elements are reduced in the electrolysis of aqueous solution?

Answer 35

In aqueous solution, there is hydrogen and oxygen from the water. The metal is more reactive than hydrogen gas will be produced at the cathode is not the metal will be reduced. Is there is a halide ion present then it will be oxidized at the anode and no oxygen gas will be produced.