What mass of K2CrO4 is required to prepare 250cm3 of 0.020 mol dm3 solution?
[K2CrO4 = 194.2g mol-1]
Answer Details
The problem is asking for the mass of K2CrO4 needed to make a 0.020 mol dm^-3 solution with a volume of 250 cm^3. To solve the problem, we need to use the formula:
mass = moles x molar mass
First, we need to calculate the number of moles of K2CrO4 needed. We can do this using the formula:
moles = concentration x volume
Substituting the given values, we get:
moles = 0.020 mol dm^-3 x 0.250 dm^3
moles = 0.005 mol
Next, we need to find the molar mass of K2CrO4, which is given as 194.2 g mol^-1.
Finally, we can calculate the mass of K2CrO4 needed using the formula:
mass = moles x molar mass
mass = 0.005 mol x 194.2 g mol^-1
mass = 0.971 g
Therefore, the mass of K2CrO4 needed to prepare 250 cm^3 of 0.020 mol dm^-3 solution is 0.97 g.
Option A, 0.97g, is the correct answer.