Asked by mandy
100cm^3 of a sodium hydroxide,NaOH solution contains 4.0g of solid sodium hydroxide,NaOH.40 cm^3 of phosphoric acid,H3PO4 is needed to neutralise 40cm^3 of the alkali.(RAM:H,1;O,16;Na,23;P,31)
(a)Calculate the molarity of the sodium hydroxide,NaOH solution.
(b)Calculate the molarity of the phosphoric acid,H3PO4.
(a)Calculate the molarity of the sodium hydroxide,NaOH solution.
(b)Calculate the molarity of the phosphoric acid,H3PO4.
Answers
Answered by
DrBob222
3NaOH + H3PO4 ==> Na3PO4 + 3H2O
mols NaOH = grams/molar mass = 4.0/40 = 0.1 mol.
a) M NaOH = mols/dm3 = 0.1mol/0.1 dm3 = 1M
b) From the equation, 3 mol NaOH = 1 mol H3PO4; therefore, 40 cc (0.04 dm3) of NaOH x 1 M = 0.04 mols NaOH.
mols H3PO4 = 1/3 of that or 0.04/3 = about 0.0133 mols.
Then M H3PO4 = mols H3PO4/dm3 H3PO4.
mols NaOH = grams/molar mass = 4.0/40 = 0.1 mol.
a) M NaOH = mols/dm3 = 0.1mol/0.1 dm3 = 1M
b) From the equation, 3 mol NaOH = 1 mol H3PO4; therefore, 40 cc (0.04 dm3) of NaOH x 1 M = 0.04 mols NaOH.
mols H3PO4 = 1/3 of that or 0.04/3 = about 0.0133 mols.
Then M H3PO4 = mols H3PO4/dm3 H3PO4.
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