14.8 g of a salt (z)dissolved in 250 cm3 of distilled water gives a concentration of 0.80 mol dm-3. Calculate the molar mass of the salt (z).

  • A 13.5 g mol-1
  • B 18.5 g mol-1
  • C 47.4 g mol-1
  • D 74.0 g mol-1
waec 2007chemistry

The correct answer is D. 74.0 g mol-1

250cm3 of distilled water contains 14.8g of salt(z)

1cm3 of distilled water will contain \(\frac{14.8 x 1}{250}\) of salt (z)

:. 1000cm3 of distilled water will contain \(\frac{14.8 x 1 x 1000}{250}\) = 59.2g/dm33 = \(\frac{concentration in g/dm3}{molar mass}

0.80 = \(\frac{59.2}{molar mass}\)

molar mass = \(\frac{59.2}{0.80}\) = 74.0 g/mol

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