Answer:
640.59 g of NaCl.
Explanation:
Using Boiling point elevation,
ΔTb = kb * i * b
Where,
b = molality
kb = 0.52 °C kg/mole
i = van't koff factor
ΔTb = ΔTsol - ΔTsolv
= 2°C
2 = 0.52 * b
= 3.846 mol/kg.
Mass of water, solvent = 2.85 kg
Molality is the ratio of the number of moles of the solute to the mass of the solvent.
= 3.846 * 2.85
= 10.96 mol.
Mass of NaCl = molar mass * number of moles
= 58.44 * 10.96
= 640.59 g of NaCl.
Let Mass be m
If its doubled then

Hence force also needs to be doubled.
Answer:
The change in height of the mercury is approximately 2.981 cm
Explanation:
Recall that the formula for thermal expansion in volume is:

from which we solved for the change in volume
due to a given change in temperature 
We can estimate the initial volume of the mercury in the spherical bulb of diameter 0.24 cm ( radius R = 0.12 cm) using the formula for the volume of a sphere:

Therefore, the change in volume with a change in temperature of 36°C becomes:

Now, we can use this difference in volume, to estimate the height of the cylinder of mercury with diameter 0.0045 cm (radius r= 0.00225 cm):
