Energy of sublimation of na(s) = 97 kj/mol bond energy of hbr = 363 kj/mol ionization energy of na(g) = 496 kj/mol electron affinity of br(g) = –324 kj/mol lattice energy of nabr(s) = –781 kj/mol bond energy of h2 = 432 kj/mol calculate the net change in energy for the following reaction: 2na(s) + 2hbr(g) → 2nabr(s) + h2(g)

Answer : The concentration can be expressed as, 1.99 M, or 15.1(m/m)%, or 18(m/v)%

Solution : Given,

Volume of solution = 0.5 L = 500 ml        (1 L = 1000 ml)

Mass of solution = 596 g

Mass of oxalic acid, (solute) = 90 g

Molar mass of oxalic acid = 90.03 g/mole

First we have to calculate the concentration in terms of M(molarity).

Molarity : Molarity is defined as the number of moles of solute present in one liter of solution.

Formula used :

where,

M = molarity of solution

= mass of solute(oxalic acid)

= molar mass of solute(oxalic acid)

= volume of solution(in liters)

Now put all the given values in this formula, we get

Now we have to calculate the concentration in terms of (m/m)%

(m/m)% : It is defined as the mass of solute present in mass of solution in grams.

Formula used :

where,

= mass of solution

Now we have to calculate the concentration in terms of (m/v)%

(m/v)% : It is defined as the mass of solute present in one milliliter of solution.

Formula used :

where,

= mass of solution