Topic 2 - Quantitative Analysis

Question 1

Moles formula of solids

Answer 1

Moles = Mass/Mr

Question 2

Moles formula of solutions

Answer 2

moles = concentration x volume

Question 3

What is hard water?

Answer 3

Hard water contains Ca2+ andMg2+ ions because the water flows over rocks containing magnesium sulfate or calcium carbonate. It wont easily form a lather with soap and makes scum instead.

Question 4

What is temporary hardness caused by

Answer 4

Calcium hydrogencarbonate (Ca(HCO3)2)

Question 5

What is permanent hardness caused by

Answer 5

Dissolved calcium sulphate

Question 6

How do you remove temporary hardness

Answer 6

Boil it and the calcium hydrogencarbonate decomposes to from insoluble CaCO3.

Question 7

How do you remove permanent hardness

Answer 7

Ion exchange resin. Contains lots of sodium or hydrogen ions and ‘exchanges’ them for calcium or magnesium ions in the water.

Question 8

Word equation for removing temporary hardness

Answer 8

Calcium hydrocarbonate -> calcium carbonate + water + carbon dioxide.

Question 9

symbol equation for removing temporary hardness

Answer 9

Ca(HCO3)2 (aq) -> CaCO3 (s) + H2O (l) + CO2 (g)

Question 10

Symbol equation for removing permanent hardness

Answer 10

Na2Resin(s) + Ca2 (aq) -> CaResin (s) + 2Na+ (aq)

Question 11

What are titrations used for

Answer 11

to find concentration

Question 12

what type of reaction is a titration

Answer 12

neutralisation

Question 13

What is the ionic equation for a titration

Answer 13

H+ (aq) + OH- (aq) -> H2O(l)

Question 14

*How do you do a titration

Answer 14

wash burette and fill with acid
use pipette to put 25cm of alkali into conical flask
add suitable indicator
add acid slowly to alkali, near end point drop by drop, until indicator changes colour
repeat until you get concordant results

Question 15

*What indicators are used in titrations

Answer 15

Phenolphthalein Pink - clear

Methyl Orange yellow - red

Question 16

How do you make a soluble salt using an acid and an insoluble reactant (base)

Answer 16

add base to acid, solid will dissolve.
Filter excess solid to get solution
Heat to slowly evaporate water and crystallize salt

Question 17

How do you make a soluble salt using an acid and a soluble reactant

Answer 17

have to put exact amount in to neutralise, can’t put in too much and filter out whats left because reactants are soluble.
Do titration to find out how much alkali is needed to neutralise.
Then carry out experiment without indicator so it is not contaminated.
The solution that remains contains only salt and water so evaporate off the water and you will be left with a pure dry salt.

Question 18

Equation of copper oxide and hydrochloric acid

Answer 18

CuO + 2HCl -> CuCl2 + H2O

Question 19

equation of sulphuric acid and sodium hydroxide

Answer 19

H2SO4 + 2NaOH -> Na2SO4 + H2O