Chemistry-Paper1-Chemical changes

Question 1

What is acid?

Answer 1

Acids form acidic solutions in water. Acids produce hydrogen ions, H+ in aqueous solution. For example:

HCl(aq) → H+(aq) + Cl-(aq)

Question 2

What is the pH value of an acid?

Answer 2

Less than 7

Question 3

What colour is acid shown on the pH scale?

Answer 3

Red

Question 4

What is alkali?

Answer 4

Alkalis form alkaline solutions in water. Alkalis produce hydroxide ions, OH- in aqueous solution. For example:

NaOH(aq) → Na+(aq) + OH-(aq)

Question 5

What is the pH value of an alkali?

Answer 5

More than 7

Question 6

What colour is alkali shown on pH scale ?

Answer 6

Blue

Question 7

What is the pH value of a neutal solution?

Answer 7

7

Question 8

What colour is neutal solution shown on the pH scale?

Answer 8

Green

Question 9

What are the two indicators of pH value?

Answer 9

• Universal indicator
• Litmus paper

Question 10

What is a base in a neutalisation reaction?

Answer 10

A substance that reacts with an acid to neutralise it and produce a salt.

Question 11

Bases that are soluble in water are called _______.

Answer 11

Alkalis

Question 12

What is a neutralisation reaction?

Answer 12

A neutralisation reaction is a reaction between an acid and a base.

Question 13

Acids are source of __________ ___.

Answer 13

Hydrogen ions, H+

Question 14

Alkalis are source of ______ ___.

Answer 14

Hydroxide ions, OH-

Question 15

When a metal react with acids, it produces what?

Answer 15

Salt + Hydrogen

Question 16

When a metal oxide react with acids, it produce what?

Answer 16

Salt + Water

Question 17

When a metal carbonate react with acids, it produce what?

Answer 17

Salt + Water + Carbon dioxide

Question 18

What is a dilute solution?

Answer 18

A dilute solution contains a relatively small amount of dissolved solute.

Question 19

What is a concentrated solution?

Answer 19

A concentrated solution contains a relatively large amount of dissolved solute

Question 20

What is a strong acid?

Answer 20

Strong acids completely dissociate into ions in solution.

Question 21

What is a weak acid?

Answer 21

Weak acids only partially dissociate in solution.

Question 22

How to calculate the pH value of acid change by the concentration of the hydrogen ions?

Answer 22

If the hydrogen ion concentration in a solution increases by a factor of 10, the pH of the solution decreases by 1 unit.