chemistry

A solution is made by adding 5.0 g Na2CO3 * 10H2O to enough water to make a 500 mL solution. what is the molarity.
I have: M=mol solute/liter solution = (5/286)/.5 = .035M
286 is what i got for the molar mass of Na2CO3 * 10H2O

Is that correct?? I think it is, but the next problem refers back to that problem and makes me think i did something wrong:

How much of this 500 mL solution should be used and diluted to make 250 mL of a .035 M solution

if the concentration is already .035 shouldnt it just be 250 mL????????

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1. It looks ok to me.

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