# concentration calculation equation?Help?Watch

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#1
Hey.. im working through a sheet from Chemistry and just wanted some help with what equations to use as not back in chemistry till Tuesday -

Q - Calcualte the concentrations of the following solutions -

9.5g of Magnesium Chloride,MgCl2 dissolved in water and made up to 100.cm3?

I think im just having a right thick day.. no chemistry over christmas + a break = forgetfull Katie!!

Thanks!
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6 years ago
#2
Use the equation concentration = moles/(volume (〖dm〗^3))

You have your total volume of 100cm3 for the bottom half of the equation. To convert this to dm3, you have to divide by 1000, which gives 0.1dm3

Next, you need the moles for the top half. Use the equation moles = (mass (g))/Mr. You are given the mass of 9.5g, and can work out the Mr to be 95.3 (24.3+2x35.5). Sub these values into the equation, and this gives you 0.10 to 2 decimal places.

Put these values into your original equation for concentration to get 0.1/0.1 = 1moldm3
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