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Qualification => Subject Doubts => GCE O - Level => Sciences => Topic started by: CMayor on April 20, 2011, 05:38:13 am

Title: chemistry
Post by: CMayor on April 20, 2011, 05:38:13 am

 N2O4 is a poisonous gas. It can be disposed of safely by reaction with sodium hydroxide.
N2O4(g) + 2NaOH(aq) ? NaNO3(aq) + NaNO2(aq) + H2O(l)
What is the minimum volume of 0.5 mol dm–3 NaOH(aq) needed to dispose of 0.02 mol of N2O4?
A 8 cm3 B 12.5 cm3 C 40 cm3 D 80 cm

PLEASE HELP

Title: Re: chemistry
Post by: NotAbod on April 20, 2011, 09:16:39 am

N2O4 + 2NaOH
u need to dispose 0.02 mol N2O4
use mole ratio to find moles of sodium hydroxide:
   1N2O4   +   2NaOh
      0.2              x
cross multiply, u need 0.04mol sodium hyrdoxide to dispose 0.02mol N2O4.
calculate the volume of NaOH needed using the formula :  moles / concentration
volume= 0.04/ 0.5(given in the question) = 0.08 dm3
to conver dm3 to cm3 multiply by 1000,
0.08 x 1000= 80 cm3, answer D


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Title: Re: chemistry
Post by: NotAbod on April 20, 2011, 09:37:24 am

solved in a better way  ;)