chemistry mock questions

Question 1

disadvantages of litmus paper (2)

Answer 1

-only shows if it’s either acidic or alkali
-does not show how acidic or alkali the solution is

Question 2

why can carbonates and hydroxides not conduct electricity/are not soluble?

Answer 2

common carbonates and hydroxides are insoluble and cannot conduct electricity as they are held in a fixed lattice structure.

Question 3

what is the percentage by mass formula?

Answer 3

mass of chemical
————————- x 100
mass of compound

Question 4

when we write diatomic particles on the products side what do we add next to them?

Answer 4

a 2

Question 5

before electrolysis is carried out, what should be done to electrodes before their masses are determined?

Answer 5

electrodes should be cleaned with emery paper to remove impurities

Question 6

explain in terms of ions the mass of two electrodes using copper sulfate solution and copper electrodes (3)

Answer 6

-at the anode copper atoms are oxidised
-copper ions move to the cathode
-cathode is reduced which causes the mass to increase

Question 7

why is graphene a good conductor of electricity (3)

Answer 7

-carbon has 4 outer shell electrons
- 3 electrons used in bonds
-delocalised electrons

Question 8

explain why a reaction between metal y and excess dilute sulfuric acid stopped even though there was solid metal y left. (2)

Answer 8

-metal sulfate is insoluble and forms a barrier
that prevents further reaction of metal with acid

Question 9

what is a weak acid (2)

Answer 9

-partially ionising
-concentration of H+ ions is lower

Question 10

how do you calculate the molecular formula from the empirical formula

Answer 10

Mr divided by the molar mass of an empirical formula