Mole ratio

2009-04-08 8:51 am

Mixture of MCO3 and NHCO3 is titrated against H2A.110cm^3 of 0.05M H2A is used for complete reaction. 168cm^3 of CO2 gas is collected. What is the mole ratio of MCO3 to NHCO3?
A.3:5
B.5:3
C.4:3
D.3:4

Please answer in ENGLISH with details.

回答 (1)

老爺子

2009-04-08 9:22 am

✔ 最佳答案

The answer is C.

Assume that the numbers of moles of MCO3 and NHCO3 are h mol and k mol respectively.

MCO3 + H2A → MA + H2O + CO2
No. of moles of MCO3 used = h mol
No. of moles of H2A used = h mol
No. of moles of CO2 formed = h mol

2NHCO3 + H2A → N2A + 2H2O + 2CO2
No. of moles of NHCO3 used = k mol
No. of moles of H2A used = k/2 mol
No. of moles of CO2 formed = k mol

Total no. of moles of H2A used :
h + (k/2) = 0.05 x (110/1000)
h + (k/2) = 0.0055
2h + k = 0.011
14h + 7k = 0.077 ...... (1)

Total no. of CO2 formed：
h + k = 168/24000
h + k = 0.007
11h + 11k = 0.077 ...... (2)

(1) = (2)
14h + 7k = 11h + 11k
3h = 4k
h : k = 4 : 3
=

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