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# What is the total concentration of Na+ ions in the mixture formed? CHEMISTRY help watch

The answer should be in mol dm -3. Also, numbers following should be subscripts! Thanks

A student mixes 100 cm3 of 0.200 mol dm–3 NaCl(aq) with 100 cm3 of 0.200 mol dm–3 Na2CO3(aq).

What is the total concentration of Na+
ions in the mixture formed?
2. Write out the dissociation reactions for each compound
NaCl (aq) --> Na^+ (aq) + Cl^- (aq)
Na2CO3 (aq) --> 2Na^+ (aq) + CO3^2- (aq)

How many moles are there in 100cm^3 of 0.200 moldm^-3 NaCl?
0.1 * 0.200 = 0.02 mol.
The ratio of NaCl to Na+ is 1:1, so there will 0.02mol of Na+ coming from the NaCl

How many moles are there in 100cm^3 of 0.200 moldm^-3 Na3CO3?
0.1 * 0.200 = 0.02 mol.
The ratio of Na2CO3 to Na+ is 1:2 so there will be 2 * 0.02 = 0.04 mol. of Na+ coming from the Na2CO3

Altogether there is 0.04 + 0.02 = 0.06 mol. of Na+ in the solution. There is also 100cm^3 + 100cm^3 = 200cm^3 total volume in the solution.

So the concentration of Na+ ions is 0.06 * (1000/200) = 0.3moldm^-3

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Updated: January 8, 2017
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