0.50g of an organic compound was kjeldahlised and the NH3 evolved was absorbed in a certain volume of 0.5M H2SO4. The residual acid required 60cm3 of M/2 NaOH. If the percentage of N is 56, then the volume of 0.5M H2SO4 taken was:
A
30 ml
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B
40 ml
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C
50 ml
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D
60 ml
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Solution
The correct option is C 50 ml from kjeldahlised method: %N2=1.4×meq.ofH2so4usedtoneutralizeNH3massofcorpd =1.4×2M(v−v12)m Val of H2so4ofMalarity≠M[or(2M)narmality]=Vml. Val.ofNaoHofMolarityM(or(M)normally)=V1ml. used for titration cocess of H2so4 m.q of excers H2so4=mer.qNaoH=MV1mer. Total meq.ofH2so4taken=2MV meqofH2so4used=2MV−MV1=meqofNH3 ∴56=1.4××2×0.5(v−602)0.50=28(V−30)⇒20=v−30 V=50ml.