Question

1/ Calculate the volume of 0.280-M NaOH solution needed to completely neutralize 27.4 mL of a 0.560-M solution of the monoprotic acid HBr.

2/ To determine the molar mass of an organic acid, HA, we titrate 1.047 g of HA with standardized NaOH. Calculate the molar mass of HA assuming the acid reacts with 37.17 mL of 0.469 M NaOH according to the equation

HA(aq) + NaOH(aq) → NaA(aq) + H₂O(ℓ)

3/

2 NaBH₄(aq) + H₂SO₄(aq) → 2 H₂(g) + Na₂SO₄(aq) + B₂H₆(g)

What volume, in mL, of a 0.504 M solution of NaBH₄ is required to produce 0.539 g of B₂H₆? H₂SO₄ is present in excess.

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Answer 1

1) calculate mole of HBr

no of mole = molarity volume of solution in liter

no of mole of HBr = 0.560 M 0.0274 L= 0.015344 mole

HBr react with NaaOH in equimolar proportion therefore 0.015344 mole of NaOH required for neutrilization

volume of solution in liter = no. of mole / molarity

volume of NaOH required = 0.015344 / 0.280 =0.0548 L = 54.8 ml

2)

no of mole = molarity volume of solution in liter

no of mole of NaOH = 0.469 M 0.03717 L= 0.01743273 mole

organic acid is HA therefore react with NaOH equimolar proportion than mean 1.047 gm = 0.01743273 mole

then 1 mole = 1 1.047 / 0.01743273 = 60.06 gm

molar mass of organic acid HA = 60.06 gm

3) molar mass of B₂H6 = 27.67 gm/mol then 0.539 gm = 0.539 / 27.67 = 0.0194795808 mole

according to reaction 2 mole of NaBH₄ produce1 mole of B₂H₆ then to produce 0.0194795808 omole of B₂H₆ requ

ired 0.0194795808 2 = 0.0389591616 mole of NaBH₄

volume of NaBH₄  = 0.0389591616/0.504 = 0. 0773 L = 77.3 ml