Calculate the amount in mole

[Voltman]

For a 0.20 M solution of potassium sulfate, K2S04, calculate the amount, in mol, of:

potassium ions, K+

[Sonic]

For a 0.20 M solution of potassium sulfate, K2S04, calculate the amount, in mol, of:

potassium ions, K+

The amount of potassium ions is calculated from the ratio of K+ in the whole molecule. In this case it is 2/(2+1+4) = 2/7 which means that for each mole of K2SO4 there are 2/7 moles of K+

Since no volume is given in the question the number of moles cannot be worked out. As 0.2M = 0.2 moles/dm^3 we can find multiply this by 2/7 as given about to give the concentration of K+ as 2/7 * 0.2 = 2/35 = 0.0571 moles/dm^3 = 2/35 M.

The number of moles of K+ is given by 2/35 * V where V is the volume in dm^3 or Litres. Note that 1dm^3 = 1000cm^3 = 10^-3m^3