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15 mL 1 N H_(2) SO_(4), 25 mL of 4 N HNO_(3), and 20 mL of X M HCl were mixed and made up to 1000 mL. Prepared by dissolving 4.725 g of pure Ba(OH)_(2). 8H_(2) O in water made up to 0.25 litre. What is the molarity of HCl solution (i.e. find X)

Answer»

Solution :`15 mL` of `1 M H_(2) SO_(4) + 25 mL of 4 M HNO_(3) + 20 mL of X M HCL`
`:. N_(1) V_(1) + N_(2) + V_(2) + N_(3) V_(3) = N_(4) V_(4)``(V_(4) = 1000 mL)`
`15 xx 2 + 25 xx 4 + 20 X = N_(4) xx 1000`
`:. N_(4) = ((130 + 20 X)/(1000))`
mEq of mixture of acid = mEq of `Ba(OH)_(2)`
`Mw of Ba (OH)_(2). 8H_(2) O = 137.4 + 34 + 18 xx 8 = 315.4`
`Ew = (315)/(2) = 157.7 g`
`N of Ba(OH)_(2) .8H_(2) O = (W_(2) xx 1000)/(Ew_(2) xx V_(SOL) ("in" mL))`
`= (4.725 xx 1000)/(157.7 xx 250)`
`0.1198 N ~~ 0.12 N`
mEq of acid mix = mEq of `Ba(OH)_(2)`
`20 xx N_(4) = 26 xx 0.12`
`N_(4) = (26 xx 0.12)/(20) = 0.156 N`
`implies (130 + 20 X)/(1000) = 0.156`
`:. X = (0.156 xx 1000 - 130)/(20) = 1.3`
`N` or `M HCl = 1.3`


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