Gaseous diborane reacts according to the balanced equation. When 7.73 mol of O 2

Question

Gaseous diborane reacts according to the balanced equation. When 7.73 mol of O2 is reacted, calculate the sign and magnitude (kJ) of the heat produced.
Express your answer in scientific notation.

B2H6(g) + 3 O2(g) ? B2O3(s) + 3 H2O(g) .

Gaseous diborane reacts according to the balanced equation. When 7.73 mol of O2 is reacted, calculate the sign and magnitude (kJ) of the heat produced.
Express your answer in scientific notation.

B2H6(g) + 3 O2(g) ? B2O3(s) + 3 H2O(g) .

Enthalpy (kJ) ?H = -2165.9 Molar Mass B2H6 27.670 O2 31.999 B2O3 69.620 H2O 18.015

Explanation / Answer

Find the number of moles of H2O

#moles = mass / molar mass
= 7.73g / 18.015g/mole = 0.4291 moles

according to the coefficients of the balanced equation
3 moles H2O are produced from 1 mole B2H6

therefore
moles B2H6 = moles H2O / 3
= 0.4291 moles / 3 = 0.143 moles

combustion of 1 moles of B2H6 produces 2165.9KJ
therefore
heat produced = 0.143 moles * 2165.9KJ / 1 mole
=

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