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# concentration calculation

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1. 3N02 (g) + H2O (l) = 2HNO3 (aq) + NO (g)

calculate the concentration of nitric acid produced when 0.543mol of NO2 is reacted with water and the solution is made up to 250cm3

so I understand the first part:

0.543mol x 2/3 = 0.362mol

but then the mark scheme goes on to say for the second mark:

0.362mol x 1000/250 = 1.45 (moldm-3)

so my issue is; what does the 1000/250 show, what is it an equation for (also units for each) and where did the 1000 come from in the first place?

any help would be appreciated
2. (Original post by BarnabyIJT)
3N02 (g) + H2O (l) = 2HNO3 (aq) + NO (g)

calculate the concentration of nitric acid produced when 0.543mol of NO2 is reacted with water and the solution is made up to 250cm3

so I understand the first part:

0.543mol x 2/3 = 0.362mol

but then the mark scheme goes on to say for the second mark:

0.362mol x 1000/250 = 1.45 (moldm-3)

so my issue is; what does the 1000/250 show, what is it an equation for (also units for each) and where did the 1000 come from in the first place?

any help would be appreciated
1000/250 scales up the moles per 250 ml into moles per litre (1000ml), which is the unit for concentration
3. (Original post by charco)
1000/250 scales up the moles per 250 ml into moles per litre (1000ml), which is the unit for concentration
Aha, I see so it's 1000/250 to give 4 because conc is in moldm-3 and before I only had a 1/4 of that amount (so to multiply 250cm3 by 4 gives me the litre); thank you! it evidently wasn't as complicated as I had envisaged.

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