(A) Mixture A: (NaOH+Na2CO3)
pmEqqmEq–––––––––––––
100 mL
With phenolphthalein: (NaOH reacts completely and 1/2mEq of Na2CO3 reacts)
p+q2=a×1 ....(i)
with methyl orange (both react completely):
p+q=b×1 ....(ii)
Solve: q2=(b−a),q=2(b−q)
mmoles of Na2CO3(q)=2(b−a)
mmoles of Na2CO3(q)=2(b−q)2=(b−a)mmol
(B) Mixture B: (NaHCO3+Na2CO3)
rmEqsmEq–––––––––––––
100 mL
With phenolphthalein: (NaHCO3 does not react)Na2CO3 react half)
∴s2=x×1mEq of Na2CO3
s=2xmEq of Na2CO3=2x2
=xmmol of Na2CO3
With methyl orange (both reacts completely):
r+s=y×1 mEq
r+2x=y
(D)r=(y-2x) mEq =mmolesofNaHCO_{3}(C)NaOH$ in Mixture A:
Solve equations (i) and (ii)
2p+32q=a+b
Substitute the value of q=2(b−a)
2p+3/2×/2(b−a)=a+b
2p=a+b−3b+3a=4a−2b
p=(2a−b)MEq= mmoles of NaOH