Making Soluble Salts

Question 1

how do you make a soluble salt

Answer 1

• by reacting an acid that contains one of the ions you want in the salt
• with an insoluble base that contains the other ion you need
• often a metal oxide or metal hydroxide

Question 2

what is the process for making a soluble salt

Answer 2

• heat the acid in a water bath
• add the base to the acid
• the base and acid will react to produce soluble salt
• filter off the excess solid to get s solution containing only the salt and water
• heat the solution gently using a bunsen burner
• leave the solution to cool and allow the salt to crystallise
• filter off the salt and leave it to dry

Question 3

why should you heat the acid in a water bath

Answer 3

to speed up the reaction between the acid and the insoluble base

Question 4

where should you heat the acid and why

Answer 4

• in a fume cupboard

- to avoid releasing acid fumes into the room

Question 5

when will you know when the base is in excess and all the acid has been neutralised after you have mixed the acid and base together

Answer 5

the excess solid will just sink to the bottom of the flask

Question 6

why is it important that the base should be in excess

Answer 6

so that you dont have any leftover acid in your product

Question 7

why should you heat the solution gently using a bunsen burner

Answer 7

to slowly evaporate off some of the water

Question 8

what should you get when you react copper oxide with sulfuric acid and what is the symbol equation for this

Answer 8

• copper oxide + sulfuric acid = copper sulfate + water
• CuO + H2SO4 = CuSO4 + H2O
• you should get blue crystals of hydrated copper sulfate if you leave the solution to crystallise

Question 9

why cant you tell when a reaction between an acid and a soluble alkali has finished when trying to make a soluble salt

Answer 9

• theres no signal that all the acid has been neutralised
• you cant just add excess alkali to the acid
• because the salt is soluble and would be contaminated with the excess alkali

Question 10

how do you work out when the reaction between an acid and a a soluble alkali is finished

Answer 10

• you need to work out exactly the right amount of alkali to neutralise the acid
• so you need to do a titration using an indicator

Question 11

what is the process of carrying out a titration using an indicator

Answer 11

• measure a set amount of acid into the concial flask using a pippette
• add a few drops of indicator
• slowly add the alkali to the acid using a burette until you reach the end point
• carry out the reaction using exactly the same volumes of alkali and acid nut no indicator
• the solution that remains when the reaction is complete contains only the salt and water
• slowly evaporate off some of the water and leave it to crystallise
• filter off the solid and dry it

Question 12

what is the end point that is reached when you slowly add the alkali to the acid using a burette

Answer 12

• the end point is the point at which the acid has been exactly neutralised
• and the indicator changes colour

Question 13

why shouldnt you add indicator when carrying out the reaction using the exact came volumes of alkali and acid

Answer 13

so the the salt wont be contaminated with the indicator

Question 14

what should you be left with when you filter off the solid and dry it

Answer 14

you will be left with a pure and dry salt

Question 15

what type of indicator should you use for the titration process

Answer 15

• you should use an indicator with a single and clear colour change
• such as phenlphthlein or methyl orange
• universal indicator is no good because its colour change is too gradual