What mass of K2CrO4 is required to prepare 250cm3 of 0.020 mol dm3 solution? [K2CrO4...

Chemistry

JAMB 2003

What mass of K₂CrO₄ is required to prepare 250cm³ of 0.020 mol dm³ solution?
[K₂CrO₄ = 194.2g mol^-1]

A. 0.97g
B. 9.70g
C. 19.42g
D. 97.10g

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Correct Answer: Option A

Explanation

1 mole m^-3 K₂CrO₄ contains 194.2g mol^-1 in 1000cm³
1 mole m^-3 K₂CrO₄ contains 92.2g mol^-1 in 500cm³
1 mole m^-3 K₂CrO₄ contains 48.55g mol^-1 in 250cm³
If n molm^-3 K₂CrO₄ contain 48.55
0.02 molm^-3 will contain (0.02/1) * (48.55/1) = 0.97g

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