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.(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

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.

2. Relevant equations

3. 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, Im not sure what the effect of dissolving 1.5g of limestone will even have, so Im stuck :S.

Hope you can help.

Thanks

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# Homework Help: Confused with moles

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