Question

A 0.1375-g sample of solid magnesium is burned in

aconstant-volume bomb calorimeter that has a heat capacity of
3,024J/oC. The temperature incresases by
1.126oC.Calculate the heat given off by the burning Mg,
in KJ/g and inKJ/mol.

Answer 1

a) Q = 0.025 KJ/g

b) Q = 0.602 KJ/mol

Step-by-step explanation:

ΔU = Q + W.....first law

∴ a constant volume: ΔV = 0

⇒ W = 0

⇒ ΔU = Q = CvΔT

∴ Cv = 3.024 J/°C

∴ ΔT = 1.126 °C

⇒ Q = (3.024 J/°C)×(1.126 °C ) = 3.405 J

⇒ Q = 3.405 E-3 KJ

a) Q [=] KJ/g

⇒ Q = (3.405 E-3 KJ) / (0.1375 g) = 0.025 KJ/g

b) Q [=] KJ/mol

∴ Mw Mg = 24.305 g/mol

⇒ Q = (0.025 KJ/g)×(24.305 g/mol) = 0.602 KJ/mol