Question

CH₆N_{2 (l)} + 5 O_{2 (g)} → + 2 N_{2 (g)} + 2 CO_{2 (g)} + 6 H₂O _(l) ΔH = -2600 kJ

What is the Molar Mass H₂O (2 decimal places Minimum)? In the last conversion factor what is the ratio of Heat ÷ moles H₂O from the balanced equation (4 SF Minimum) - Is the sign + or -? ΔH (in kJ) - Is the sign + or -?

The specific heat of ethanol is 2.46 J/g^oC. When 2555 J of heat are added to 32.8 g ethanol, a final temperature of 77.5^oC is reached. What was the initial temperature of the ethanol?

When a 4.00 g sample of solid ammonium nitrate dissolves in 60.0 g of water in a coffee cup calorimeter the temperature drops from 25.7 to 15.0 ^oC. Calculate the ΔH in kJ/mol for the dissolving of NH₄NO₃ in water. Assume that the specific heat of the solution is the same as that of pure water.

Heat Gained By Water			=	- Heat Lost By Solute Hydration
Mass of Solution	×	Specific Heat of Water	×	Tf - Ti (or ΔT)	=	- ΔH Hydration
______ g	×	4.184 Jg oC (or K)	×	_____ oC (or K)	=	_____J

Answer 1

CH₆N_{2 (l)} + 5 O_{2 (g)} → + 2 N_{2 (g)} + 2 CO_{2 (g)} + 6 H₂O _(l) ΔH = -2600 kJ

Molar Mass H₂O = 18 g/mol

ΔH = - Heat ÷ moles H₂O

        = - (- 2600 / 6 )

ΔH = 433.3 kJ/mol

The specific heat of ethanol is 2.46 J/g^oC. When 2555 J of heat are added to 32.8 g ethanol, a final temperature of 77.5^oC is reached. What was the initial temperature of the ethanol?

Q = m Cp ΔT

2555 = 32.8 x 2.46 x (77.5 - Ti)

Ti = 45.8

initial temperature = 45.8 ^oC