Hess's Law and Q Practice

Calculate the standard molar enthalpy of combustion for ethane, C₂H₄,

C₂H_{4 (g)} + 3 O_2(g) --> 2 CO_2(g) + 2 H₂O_(g)

H_f, C₂H_{4 (g)} = +52 kJ/mol

H_f, CO_2(g) = -394 kJ/mol

H_f, H₂O_(g) = -242 kJ/mol

• -204 kJ

• -584 kJ

• -679 kJ

• -1324 kJ

Tags

NGSS.HS-PS1-4

Calculate the standard enthalpy of combustion for the reaction

SiH_{4 (g)} + 2 O_2(g) --> SiO_2(g) + 2 H₂O_(g)

H_f, SiH_{4 (g)} = +34 kJ/mol

H_f, SiO_2(g) = -911 kJ/mol

H_f, H₂O_(g) = -242 kJ/mol

• -1187 kJ

• -1429 kJ

• -1360 kJ

• -2219 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Calculate the standard molar enthalpy of combustion for the reaction

2 NO_{2 (g)} + 7 H_2(g) --> 2 NH_3(g) + 4 H₂O_(g)

H_f, NO_{2 (g)} = +33 kJ/mol

H_f, NH_3(g) = -42 kJ/mol

H_f, H₂O_(g) = -242 kJ/mol

• -1118 kJ

• -255 kJ

• -808 kJ

• -993 kJ

Tags

NGSS.HS-PS1-4

What is the sign of the enthalpy change for an endothermic reaction?

• Positive

• Cannot be determined

• negative

• Depends on the pressure

Tags

NGSS.HS-PS1-4

What is the unit for specific heat capacity?

• J

• kg

• K

• J/(g ˑ^oC)

What is the unit for Q in the equation Q = m·Cˑ∆T?

• J

• kg

• K

• J/(g ˑ^oC)

Tags

NGSS.HS-PS3-1

Calculate the standard molar enthalpy of combustion for sucrose, C₁₂H₂₂O₁₁,

C₁₂H₂₂O_{11 (s)} + 6 O_2(g) --> 6 CO_2(g) + 11 H₂O_(g)

H_f, C₁₂H₂₂O_{11 (s)} = -2222 kJ/mol

H_f, CO_2(g) = -394 kJ/mol

H_f, H₂O_(g) = -242 kJ/mol

• -2804 kJ

• -5840 kJ

• -6790 kJ

• -1324 kJ

Tags

NGSS.HS-PS1-4

Calculate the amount of heat required to heat 357 g of ethylene glycol (antifreeze) from 0^oC to 110^oC. The specific heat of ethylene glycol is 2.42 J/(gˑK).

• 16.2 kJ

• 71.5 kJ

• 39.3 kJ

• 95.0 kJ

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-2

Calculate the specific heat of Freon-12 if it requires 29.3 joules of heat to raise the temperature of 89.1 g of this gas by 55.0^oC.

• 0.000900 J/(g·K)

• 0.00598 J/(g·K)

• 1.67 J/(g·K)

• 2.83 J/(g·K)

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

If the specific heat of a substance is low, this means that _____.

• It heats up and cools down fast.

• All answers are correct.

• Has no effect.

• It takes longer to heat up and cool down.

Tags

NGSS.MS-PS3-4

NGSS.MS-PS1-4