Adding salt to water when boiling vegetables or pasta makes the water boil at a higher temperature. how much would the boiling point of water be increased if 49.2 g of nacl is added to 500 ml of water? (remember that the density of water is 1 g/ml and kb for water is 0.51 oc/m)

Adding a non-volatile solute in solvent, increases the boiling point of solvent. This is referred as elevation in boiling point. The increase in boiling point is mathematically expressed as
ΔTb = Kb X m    ....... (1)
where, Kb = molal elevation constant =  0.51 oC/m
m = molality of solution = 

Given: weight of solute = 49.2 g
volume of solution = 500 ml
Density of water = 1 g/ml

∴  weight of solvent = 500 g = 0.5 kg

Also,we know that molecular weight of NaCl = 58.5

∴m = molality of solution = 
                                        =  1.68 m

The molality of solution is 1.68 m      ......  (2)

Substituting 2 in 1 we get 
ΔTb = Kb X m = 0.51 x 1.68 = 0.8568 oC

Thus, increase in boiling point of water is 0.8568 oC
Final boiling point of solution = 100 + 0.8565 = 100.8568 oC

The answer is a) carbon-12