Chemistry moles help?

2016-07-12 5:19 pm

1.20 dm^3 of hydrogen chloride gas was dissolved in 100 cm^3 of water.
i) how many moles of hydrogen chloride gas are present?
ii) what was the concentration of the hydrochloric acid formed?

25.0cm^3 of the acid was titrated against NaOH of concentration 0.200 mol/dm^3 to form NaCl and water
i) how many moles of acid were used?
ii) calculate the volume of NaOH used

回答 (1)

胡雪8°

2016-07-12 5:28 pm

1.
(i)
At RTP, 1 mole of gas occupies a volume of 24 dm³.
No. of moles of HCl gas = (1.20 dm³) / (24 dm³/mol) = 0.0500 mol

(ii)
Concentration of the HCl(aq) formed = (0.0500 mol) / (100/1000 dm³) = 0.500 M

2.
(i)
No. of moles of HCl(aq) used = (0.500 mol/L) × (25.0/1000) = 0.0125 mol

(ii)
HCl + NaOH → NaCl + H₂O
OR: Mole ratio HCl : NaOH = 1 : 1

No. of moles of HCl(aq) used = 0.0125 mol
No. of moles of NaOH(aq) used = 0.0125 mol
Volume of NaOH(aq) used = (0.0125 mol) / (0.200 mol/dm³) = 0.0625 dm³ = 62.5 cm³

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