Acids, Bases and Salts

Question 1

What is the pH scale?

Answer 1

A measure of how acidic or alkaline a solution is.

Question 2

If a solution has a pH less than 7, is it acidic or alkaline?

Answer 2

It is acidic. The closer the pH value is to 0, the more acidic it is.

Question 3

If a solution has a pH more than 7, is it acidic or alkaline?

Answer 3

It is an alkali or a base. The closer to 14 the number, the more alkaline it is.

Question 4

What is an alkali?

Answer 4

A soluble base

Question 5

If a solution has a pH of 7, is it acidic or alkaline?

Answer 5

It is neutral.

Question 6

What is an example of a neutral substance?

Answer 6

Pure water

Question 7

How can one test for pH?

Answer 7

Using Universal Indicator.

Question 8

What colour does Universal Indicator turn when it comes into contact with an acid?

Answer 8

Red

Question 9

What colour does Universal Indicator turn when it comes into contact with a base?

Answer 9

Purple

Question 10

What colour does Universal Indicator turn when it comes into contact with a neutral substance?

Answer 10

Green

Question 11

What makes a dissolved substance acidic?

Answer 11

H+ ions

Question 12

What makes a dissolved substance alkaline?

Answer 12

OH- ions

Question 13

What is a neutralisation reaction?

Answer 13

A reaction between an acid and a base.

Question 14

What is the general formula for a neutralisation reactions?

Answer 14

Acid + Base -> salt + water

Question 15

Why is water produced during a naturalisation reaction?

Answer 15

The acidic H+ ions react with the negative OH- ions to make water.

Question 16

What is the general equation for making salts from metals?

Answer 16

Acids + Metal -> Salt + Hydrogen

Question 17

Why can’t highly reactive metals be used to make salts?

Answer 17

They react explosively when mixed with acids so aren’t safe.

Question 18

Why can’t unreactive metals be hard to make salts?

Answer 18

The reaction would be too slow to make it worthwhile.

Question 19

How can you see how reactive metals are?

Answer 19

By monitoring the rate of hydrogen production when a metal is mixed with an acid. The rate of hydrogen production is shown by the rate of bubbles produced.

Question 20

How can one test for the presence of hydrogen gas?

Answer 20

You can put a lot splint into the test tube. If there’s a squeaky pop sound, hydrogen is present. The louder the pop, the more hydrogen there is.

Question 21

How do you name a salt from a reaction with a metal?

Answer 21

The first half of the name is the metal. The second part of the name is the name of the non-acidic ion from the acid.

Question 22

What salts does hydrochloric acid produce?

Answer 22

Chloride salt

Question 23

What slats does sulphuric acid produce?

Answer 23

Sulphate salts

Question 24

What is the general equation of making salts from metal (hydr)oxides?

Answer 24

Acid + Metal (Hydr)Oxide -> Salt + Water

Question 25

How do you name the salt from a reaction with a metal (hydr)oxide?

Answer 25

The first half of the name is the metal name from the (hydr)oxide. The second half of the name is the name of the non-acidic ion from the acid.

Question 26

How does one make a salt from ammonia?

Answer 26

You can react ammonia with nitric acid to make ammonium nitrate. Ammonia + Nitric acid -> Ammonium nitrate NH3(aq) + HNO3(aq) -> NH4NO3(aq)

Question 27

What is a use of ammonium nitrate?

Answer 27

Fertiliser

Question 28

How does one make a soluble salt from a metal or insoluble salt?

Answer 28

1) Put the acid in a beaker and mix with the insoluble reactant. 2) Keep adding the insoluble reactant until it is in excess. 3) User filter paper and a filter funnel to get the salt solution.

Question 29

How do you make a soluble salt from an alkali?

Answer 29

You have to add expectations the right amount of alkali to neutralise the acid - Universal Indicator can be used to show when the reaction has finished. Then, take note of the quantities and repeat again without Universal Indicator so that the salt isn't contaminated.

Question 30

How does one get salt crystals from a salt solution?

Answer 30

1) Heat the solution to evaporate most of the water | 2) Leave to cool at room temperature and the salt will crystallise

Question 31

How does one make an insoluble salt?

Answer 31

Using a precipitation reaction. Just pick two aqueous solutions containing the required ions and mix them. You can then filter the salt out.

Question 32

What are three other uses of precipitation reactions?

Answer 32

* To remove poisonous ions from drinking water * Softening water * Sewage treatment