Calculating % of Calcium Carbonate in Limestone

[Trail_Builder]

I thought I knew moles inside out, but I havnt quite been told how to factor in what happens when you dissolve something in something.

Homework Statement

1.500g of a sample of limestone was dissolved in 50cm^3 of a 1.00 mol/dm^3 of hydrochloric acid solution. The resulting solution was made up to 250cm^3 precisely with distilled water. 25.0cm^3 of this solution required 21.05cm^3 of 0.100 mol/dm^3 of sodium hydroxide for neutralisation.

Calculate the % of rock which is calcium carbonate.

Homework Equations

The Attempt at a Solution

mol of HCL:

mol = (vol/1000)*conc
50cm^3 is 1 mol/dm^3, so added with water up to 250cm^3 will be 0.2 mol/dm^3

mol(HCl) = 0.250*0.2
mol(HCl) = 0.05

but then we only take 25cm^3, so...

mol(HCl) = 0.005

mol of NaOH:

mol(NaOH) = (vol/1000)*conc
mol(NaOH) = (21.05/1000)*0.1

mol(NaOH) = 0.002105


Now I get stuff, I am not sure what the effect of dissolving 1.5g of limestone will even have, so I am stuck :S.


Hope you can help.


Thanks

 

[mgb_phys]

1.500g of a sample of limestone was dissolved in 50cm^3 of a 1.00 mol/dm^3 of hydrochloric acid solution. The resulting solution was made up to 250cm^3 precisely with distilled water. 25.0cm^3 of this solution required 21.05cm^3 of 0.100 mol/dm^3 of sodium hydroxide for neutralisation.

The NaOH is needed to neutralise any HCl that wasn't 'used up' by the limestone - you just have to work backwards.

1, Work out many moles of NaOH
2, How many moles of HCl would this react with
3, How much HCl was made up originally.
4, - subtract (2)
5, how much CaCO3 would this HCl react with?

 

[Trail_Builder]

so for 1) I have 0.002105
for 2) 0.002105 (because 1:1 ratio)
3) 0.005
4) 0.002895
5) 0.0014475 mol of CaC03 right? (because the equation would be CaCO3 + 2HCl goes to CaCl2 + H2O + CO2, so 1:2 ratio)

just checking lol.

thanks for your help :D