The most exothermic 'ordinary' chemical reaction for a given mass of reactants is 2H(g) → H 2 (g); Δ E = 103 kcal. The theoretical decrease in mass on combination of 2.0 moles of hydrogen at

Question

The most exothermic 'ordinary' chemical reaction for a given mass of reactants is 2H(g) → H 2 (g); Δ E = 103 kcal. The theoretical decrease in mass on combination of 2.0 moles of hydrogen atoms to form 1.0 mole of hydrogen molecules, assuming that the energy is released only due to decrease in mass of the system, is

TestHub · Accepted Answer

The energy released is 103 kcal = 103 × 4.184 × 10³ J = 4.31 × 10⁵ J.

Using Einstein's mass-energy equivalence formula, E = Δ m c², where c = 3 × 10⁸ m/s:

Δ m = E/c2

Δ m = (4.31 × 105 J)/((3 × 108 m/s)2)

Δ m = (4.31 × 105)/(9 × 1016) kg

Δ m = 4.8 × 10^-12 kg

This corresponds to option (a).

Chemistry - Thermochemistry Question with Solution | TestHub

Options:

Doubts & Discussion