moles and concentrations

[mollykins]

I have two questions i hope someone will check, to see if i'm doing them right, please;

1)what volume of 0.1m of sulfuric acid contains 0.002 moles

would the answer be, 98 (the relative molecular mass) x 0.002 , then either divided or multiplied by 0.1?

2) 4.24g of Na2CO3 is dissolved in water and the solution is made up to 250ml. what is the concentration of the solution in mol dm^-3 ?

would you, say there's 106g in 1dm^-3 (or 1 mol), then divide that by 4.24 to get 25 mol dm^-3, then divide that by 40 to find the mol dm^-3 ? which I make to be 0.625 mol dm^-3 ????????????????????

[jomifl]

assuming you are referring to Q2. If you divide the weight of sodium carbonate by the molecular weight that gives you the number of moles, if this was dissolved in 1litre it would be the same as the molar strength of the solution. You are dissolving it in only 0.25 litres so it will be proportionately stronger, you can do the calculations.
to summarise;
weight of NaCO3/molecular weight X 1000ml/250ml