EL 9: How salty?

Question 1

What is an acid?

Answer 1

A compound that disassociates in water to produce hydrogen ions

Question 2

What is a base?

Answer 2

A compound that reacts with an acid - is a proton acceptor - to produce water and a salt

Question 3

What is neutralisation?

Answer 3

When an acid and alkali react and a salt is formed

Question 4

What is an alkali?

Answer 4

A base that dissolves in water to produce hydroxide ions (OH-)

Question 5

What is a salt?

Answer 5

Is a product of neutralisation (when a H+ of an acid is replaced by a metal ion)

Question 6

What is a strong acid?

Answer 6

Fully dissociates in an aqueous solution

Question 7

What is a weak acid?

Answer 7

Partially dissociates in an aqueous solution

Question 8

What is a key property of the group 2 oxides and hydroxides?

Answer 8

They are bases, they react with acids to produce salts

Acid + Base = Salt + Water

Question 9

What is the general definition of an acid?

Answer 9

A substance that donates H+ in a chemical reaction

Question 10

What is the general definition of a base?

Answer 10

A substance that accepts the H+ in a chemical reaction

Question 11

What do you need before you can start a titration?

Answer 11

A standard solution

Question 12

What is a standard solution?

Answer 12

Any solution that you know the concentration of

Question 13

What does an acid + metal carbonate =?

Answer 13

Salt + H2O + CO2

Question 14

What does an acid + Metal =?

Answer 14

Salt + H2

Question 15

What does an acid + Metal oxide =?

Answer 15

Salt + H2O

Question 16

What does an acid + Metal hydroxide =?

Answer 16

Salt + H2O

Question 17

When making a standard solution must the bottom of the meniscus reach the line?

Answer 17

To make sure its accurate, you need to carry out every technique to the same level of precision

Question 18

When making a standard solution must you invert the volumetric flask with the solution when its done?

Answer 18

To make sure its all mixed and to check the level of the meniscus again

Question 19

Why must you make sure the standard solution is a suitable concentration compared to the solution you’re titrating it against?

Answer 19

If its too dilute, you’ll have to add loads before you reach an end point. If its too concentrated then tiny amounts will cause large changes in pH and your results may be inaccurate. So you should therefore make you standard solution to a similar concentration to the solution you’re titrating it against

Question 20

What do titrations allow you to do?

Answer 20

Find put exactly how much acid is needed to neutralise a quantity of alkali

Question 21

Why is it a good idea to do a rough titration?

Answer 21

To get a rough idea where the end point of the titration is, (the point where the alkali is exactly neutralised and the indicator changes colour).

Question 22

Why do you need to do more than one accurate titration?

Answer 22

To calculate a mean titre and to see if your results are accurate

Question 23

Why do you need to use a mean titration value (0.1 leeway)

Answer 23

To get an accurate mean titre

Question 24

How do you work out the titre?

Answer 24

The final reading on the burette minus the initial reading on the burette (2 decimal places)

Question 25

Why must you wash out the conical flask between titrations?

Answer 25

To remove any acid or alkali left in it

Question 26

what does an indicator show you?

Answer 26

When a reaction has finished. In titrations, indicators that change colour quickly over a very small pH range are used so you know exactly when the reaction has ended.

Question 27

Indicator: METHYL ORANGE

Answer 27

Turns YELLOW to RED when adding acid to alkali

Question 28

Indicator: PHENOLPHTHALEIN

Answer 28

Turns RED to COLOURLESS when adding acid to alkali

Question 29

Where is the best place to place the solution with the indicator?

Answer 29

On a white surface so the colour change is easy to see

Question 30

Why can’t universal indicator be used?

Answer 30

Its colour change is too gradual

Question 31

When a solution is made, what will its concentration depend on?

Answer 31

The amount of solute and the final volume of the solution

Question 32

How is concentration calculated?

Answer 32

Concentration = amount (moles) / Volume

Question 33

How is volume calculated?

Answer 33

Volume = amount (moles) / concentration

Question 34

How are moles calculated?

Answer 34

Moles = concentration x volume