Chemistry 3a Summary Questions

Question 1

Before 1800, how were elements classified?

Answer 1

By their relative atomic mass.

Question 2

Give two reasons why Newlands’ Octaves was criticised.

Answer 2

1) he didn’t leave gaps for undiscovered elements
2) He didn’t have any evidence
3) he put metals and non-metals together

Question 3

Why did Mendeleev leave gaps in his Table of Elements?

Answer 3

For undiscovered elements.

Question 4

What does the group number mean?

Answer 4

How many electrons there are in the outer shell.

Question 5

What is shielding?

Answer 5

Inner electrons getting in the way of the nuclear charge from the nucleus.

Question 6

As you go down group one, what is the trend in reactivity?

Answer 6

As you go down group one the elements get more reactive.

Question 7

What is the density of alkali metals?

Answer 7

The first three are less dense than water so will float.

Question 8

What is the charge of a halide ion when it forms an ionic compound?

Answer 8

Negative.

Question 9

What are the properties of a transition metal?

Answer 9

1) good conductors of heat and electricity
2) dense, strong and shiny
3) less reactive than group 1 metals
4) higher melting points than group 1 metals

Question 10

What are the main ions that cause water hardness?

Answer 10

1) calcium ions

2) magnesium ions

Question 11

What are two possible health benefits of drinking hard water?

Answer 11

1) good for teeth and bones

2) reduced risk of heat disease

Question 12

What are two methods of removing permanent hardness from water?

Answer 12

1) running the water through an ion exchange column

2) adding washing soda (sodium carbonate)

Question 13

During water treatment, how are microbes killed so that the water is safe?

Answer 13

Chlorine is added to the water to kill any microbes. Chemicals are added to make microbes join together.

Question 14

Why isn’t tap water purified by distillation?

Answer 14

It is too expensive.

Question 15

Why is flouride added to some drinking water?

Answer 15

It helps prevent tooth decay.

Question 16

What is a reversible reaction?

Answer 16

A reversible reaction is one where the products if the reaction can themselves react to produce the original reactants.

Question 17

What is meant by an equilibrium?

Answer 17

Where the mass of products and reactants remain constant, the forward reaction rate is balanced by the backwards rate.

Question 18

How does changing the temperature and pressure of a reversible reaction alter the equilibrium position?

Answer 18

TEMPERATURE:
- increase = favours the endothermic reaction
- decrease = favours the exothermic reaction
PRESSURE:
- increase = encourage the reaction that produces less volume
- decrease = encourage the reaction that produces more volume

Question 19

What effect does the iron catalyst have on the reaction between nitrogen and hydrogen? (The Haber process to make ammonia)

Answer 19

It increases the rate of reaction so the temperature can be as low as possible to get a high yield, but not too slow.

Question 20

When alcohols dissolve in water, is the solution acid, neutral or alkali?

Answer 20

Neutral.

Question 21

What is the functional group in carboxylic acids?

Answer 21

-COOH.

Question 22

What are two uses of carboxylic acids?

Answer 22

1) ethanoic acid (in vinegar)

2) soaps and detergents

Question 23

What two substances react together to form an ester and what is the catalyst that is used?

Answer 23

An ester is formed from an alcohol and a carboxylic acid reacting together, and the catalyst used is an acid (for example sulphuric acid).

Question 24

What are two uses of esters?

Answer 24

1) perfumes
2) flavourings / aromas
3) ointments
4) solvents (for paint, ink, glue, nail varnish remover)