1) A solution contains 3.5g of potassium hydroxide in 250cm³. Calculate its molarity. [K=39.0, O=16.0, H=1.0]
a) Moles per litre
Step I
Work out for RFM of potassium hydroxide (KOH)
1 x K = 39 x 1 = 39
1 x O = 16 x 1 = 16 + 1 x H = 1 x 1 = 1
=56

Step II
Remember one mole is equal to the RFM of a compound.
1 mole(KOH) = 56
P moles(KOH) = 3.5g
Step III
Solve for p moles