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31/12/2021 4:27 pm
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Calculate the molarity of each of the following solutions:
(a) 30 g of Co(NO3)2.6H2O in 4.3 L of solution
(b) 30 mL of 0.5 M H2SO4 diluted to 500 mL.
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31/12/2021 4:35 pm
Molarity is given by
Molarity = \(\frac{Moles\;of\;solute}{Volume\;of\;solution\;in\;litre}\)
(a) Molar mass of Co(NO3)2.6H2O
= 59 + 2 (14 + 3 × 16) + 6 × 18
= 291 g mol-1
∴ Moles of Co(NO3)2.6H2O = \(\frac{30}{291}\)mol
= 0.103 mol
Therefore, molarity = \(\frac{0.103mol}{4.3L}\)
= 0.023 M
(b) Number of moles present in 1000 mL of 0.5 M H2SO4 = 0.5 mol
∴ Number of moles present in 30 mL of 0.5 M H2SO4 = \(\frac{0.5 \times 30}{1000}\)mol
= 0.015 mol
Therefore, molarity = \(\frac{0.015}{0.5L}\)mol
= 0.03 M