Question

Can anyone help explain the reasoning behind the answers?

I kept getting a different solution for part b and c

Answer 1

As Wikipedia says
"The limiting reagent (or limiting reactant) in a chemical reaction is the substance that is totally consumed when the chemical reaction is complete. The amount of product formed is limited by this reagent, since the reaction cannot continue without it. If one or more other reagents are present in excess of the quantities required to react with the limiting reagent, they are described as excess reagents or excess reactants."

The balanced equation of the reaction

`3CH_3COOH+Al(OH)_3->(CH_3COO)_3Al+3H_2O`

`"Molar mass of "CH_3COOH`
`=2*12+4*1+2*16=60g/"mol"`

`"Molar mass of "Al(OH)_3`
`=27+3*1+3*16=78g/"mol"`

`"Molar mass of "(CH_3COO)_3Al`
`=27+3*59=204g/"mol"`

a) By the above balanced equation the mole ratio of reactants

`CH_3COOH:Al(OH)_3=3:1`

So mass ratio should be `3xx60:1xx78=30:13`

But the ratio taken`CH_3COOH:Al(OH)_3=125:275=5:11`

As per balanced reaction 12 5g `CH_3COOH` requires
`13/30xx125g~~54g Al(OH)_3`

But `Al(OH)_3` taken is 225g. Hence `CH_3COOH` will be fully consumed but `Al(OH)_3` will be excess.

So `CH_3COOH->` limiting reagent

b) Excess `Al(OH)_3->225-54=221g`

c) By the above balanced equation the mole ratio of reactants

`CH_3COOH:(CH_3COO)_3Al=3:1`
so mass ratio should be `3xx60:1xx204=15:17`

As per balanced reaction 12 5g `CH_3COOH` produces
`17/15xx125g~~141g (CH_3COO)_3Al`

Decimal place not considered in calculation