Question

4. Rank the following solutions by increasing boiling point (or decreasing freezing point). Note: Some solutions may have the same boiling points. Indicate when boiling points are the same 1.0 M NaCl, 1.0 M CH20., 1.0 M NaNO3, 1.0M CaCl, 10 M Ca(NO3)2, 2.0 M C6H12O6, 2.0 M NaCl, 2.0 M CaCl2

Answer 1

4) elevation in boiling point is a colligative property which depends on solute concentration. More number of solute particles means more increase in boiling point ( or lesser freezing point ) . Effective concentration is calculated by multiplying van’ t Hoff factor ( i ) with concentration c.

Van’t Hoff factor is number of particles after dissociation or association for eg vant Hoff factor (i ) for NaCl = 2

( a ) 1 M NaCl

i = 2 & c = 1

i x c = 2

( b ) 1M C6H12O6 ( it is non electrolyte )

i = 1 & c = 1

i x c = 1

( c ) 1 M NaNO3

i = 2 & c = 1

i x c = 2

( d ) 1 M CaCl2

i = 3 & c = 1

i x c = 3

( e ) 1 M Ca( NO3 )2

i = 3 & c= 1

i x c = 3

( f ) 2 M C6H12O6

i x c = 2

( g ) 2 M NaCl

i x c = 2 x 2 = 4

( h ) 2 M CaCl2

i x c = 3 x 2 = 6

boiling point order

1M C6H12O6 < 2 M C6H12O6 = 1 M NaCl = 1 M NaNO3 < 1 M CaCl2 < 1M Ca( NO3 )₂ < 2M NaCl < 2MCaCl_{2 ( reverse order for freezing point )}