Acids and Alkalis

Question 1

An example of an alkali is…

Answer 1

Bleach

Question 2

All acids contain the element:

Answer 2

Hydrogen

Question 3

What is the pH of a neutral solution?

Answer 3

7

Question 4

What is the reaction between an acid and an alkali known as?

Answer 4

Neutralisation

Question 5

What is the word equation for the reaction between an acid and an alkali?

Answer 5

acid+alkali—>salt+water

Question 6

Why is heartburn treated using an alkali?

Answer 6

To neutralise the excess acid in your stomach

Question 7

How is acid rain produced from fossil fuels?

Answer 7

1. Fossil fuels are burned
2. Sulfer in the fuels reacts with oxygen in the air to form sulfer dioxide
3. Sulfer dioxide reacts with water in clouds
4. To form sulfuric acid
5. This falls as acid rain

Question 8

What salt is formed when sulfuric acid and magnesium react?

Answer 8

Magnesium sulfate

Question 9

Some students add drops of an acid onto a rock sample. They observe bubbles. What is the gas given off?

Answer 9

Carbon dioxide

Question 10

A student weighed a crucible containing steel wool. He then burned the steel wool and reweighed the crucible. The mass after burning would be:

Answer 10

More than before because you are adding oxygen

Question 11

What chemical could you use to show that carbon dioxide was produced during the reaction between hydrochloric acid and calcium carbonate?

Answer 11

Limewater

Question 12

What type of chemical is it when it is described as ‘soapy’ and when it is tested with an indicator, it is shown to have a pH of 9?

Answer 12

This chemical is an alkali because it has a pH higher than 7. Many alkalis feel soapy

Question 13

Why does a concentrated acid give a more vigorous reaction with a metal than a dilute acid with the same metal?

Answer 13

A concentrated acid contains more acid particles than a dilute acid which has fewer acid particles (dilute contains more water) so in the concentrated acid there are more acid particles to react

Question 14

How could you put a campfire out?

Answer 14

In the fire triangle there is oxygen, heat and fuel. To make it go out add no more fuel and wait until fire goes out. Cover the fire (e.g. with sand) to stop oxygen getting in. Reduce heat by pouring on water.

Question 15

METAL | OBSERVATIONS
———————————————
Unknown metal | bubbles seen, test tube became warmer
Calcium | lots of bubbles produced very quickly, test tube
| became very hot
Zinc | few bubbles seen

What is the difference of the reactivity of the unknown metal with that of calcium and zinc?

Answer 15

The unknown metal is more reactive than zinc but less reactive than calcium. The reaction of the unknown metal is more vigorous with zinc but less vigorous than with calcium.

Question 16

Colour in Acid |Colour in Alkali | Colour in Neutral
INDICATOR A red | blue | blue
INDICATOR B red | blue | purple
INDICATOR C yellow | yellow | yellow

Which is the most useful and which is the least useful? Why?

Answer 16

Indicator B is the most useful because there is a different colour for each pH area, (red for acid, blue for alkali and purple for Neutral). The second best indicator is A because the colours for acid and alkali are different, the only downside is that the colour in Neutral is the same as the colour in alkali (blue). The least most useful one is indicator C because they are all the same colour so it is useless for finding out what sort of pH it has