In: Chemistry
N2H4(l) + O2(g) --> N2(g) + 2H2O (l); ΔH= -285.8 kJ
How many kJ of heat will be released when 35.7 g water is generated?
FW: N = 14; H = 1; O = 16.
Given: Heat
released for the reaction ∆H = -285.8 kJ
Mass of water, H2O generated = 35.7 g
N2H4 (l) + O2 (g) → N2 (g) + 2 H2O (l)
Molar mass of water, H2O = 2 x Mass of H + Mass of
O
= 2 x 1 + 16 = 18g
Number of moles of water, H2O generated = Given mass of
water, H2O / Molar mass of water, H2O
= 35.7 / 18 = 1.98 mol
As is clear from the chemical equation and the given data, for 2
mol of water, H2O generated 285.8 kJ of heat is
released
⇒ For 1 mol of water, H2O generated (285.8 / 2) kJ of
heat is released
⇒ For 1.98 mol of water, H2O generated (285.8 / 2) x
1.98 kJ of heat is released
⇒ For 1.98 mol of water, H2O generated 283.42 kJ of heat
is released
Therefore heat released, ∆H = -283.42 kJ