How much solution could be heated to boiling by the heat evolved by the dissolution of 26.5 g of naoh? (for the solution, assume a heat capacity of 4.0 j/g⋅∘c, an initial temperature of 25.0 ∘c, a boiling point of 100.0 ∘c, and a density of 1.05 g/ml.)

94.642 mL

Explanation:

Given:

Mass of the NaOH,  m = 26.5 g

Heat capacity of the solution, C = 4.0 J/g°C

Initial temperature = 25.0° C

Density = 1.05 g/mL

Now,

Molat mass of NaOH = 40 g/mol

Lattice energy of (NaOH) =  887 kJ/mol

The heat of hydration (NaOH) = 932 kJ/mol.

Thus,

The heat of dissolution of 1 mol of NaOH = 887 kJ/mol - 932 kJ/mol = -45 kJ/mol.

Number of moles of (NaOH), n = (26.5 g) / (40 g/mol) = 0.6625 mol.

Now, the change in temperature, ΔT = 100°C - 25°C = 75°C.

Thus,

the heat of dissolution of 0.6625 mol of NaOH, Q = -45 kJ/mol × 0.6625 mol = - 29.8125 kJ. = - 29812.5 J

Also

Q = m'CΔT

on substituting the values in the above formula, we get

- 29812.5 J = m' × 4 J/g·°C × 75°C.

m' = mass of the solution

or

m' = 99.375 g

m' = 90 g of solution.

Now,

Density = Mass / Volume

on substituting the values, we get

1.05g/mL = 99.375 g / Volume

or

Volume of the solution = 94.642 mL

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e