A solution of sucrose (molar mass = 342 g mol$$-$$) has been prepared by dissolving 68.5 g of sucrose in 1000 g of water. The freezing point of the solution obtained will be (Kf for water = 1.86 K kg mol$$-$$1)
A
$$-$$ 0.372oC
B
$$-$$ 0.520oC
C
+ 0.372oC
D
$$-$$ 0.570oC
Explanation
Depression in freezing point,
$$\Delta $$Tf
= Kf $$ \times $$ m
m = $${{{w_B}} \over {{M_B}}} \times {{1000} \over {{W_A}}}$$
A 0.0020 m aqueous solution of an ionic compound [Co(NH3)5(NO2)]Cl freezes at $$-$$ 0.00732oC. Number of moles of ions which 1 mol of ionic compound produces on being dissolved in water will be (Kf = $$-$$1.86oC/m)
A
3
B
4
C
1
D
2
Explanation
The number of moles of ions produced
by 1 mol of ionic compound = i
0.5 molal aqueous solution of a weak acid (HX) is 20% ionised. If Kf for water is 1.86 K kg mol$$-$$1, the lowering in freezing point of the solution is
Concentrated aqueous sulphuric acid is 98% H2SO4 by mass and has a density of 1.80 g mL$$-$$1. Volume of acid required to make one litre of 0.1 M H2SO4 solution is