Thermo Review

A sample of iron receives 50.J of heat energy that raises the temperature of the iron by 25.0°C. If iron has a specific heat of 0.10 J/g°C, what is the mass of the iron sample?

• 25g

• 30g

• 20g

• 50g

Tags

NGSS.HS-PS3-4

Calculate the enthalpy of reaction (ΔH). 4CO_{2 (g)} + 6H₂O _(g) → 2C₂H_{6 (g)} + 7O_{2 (g)} ΔH_f^o [CO_2(g)] = -393.5 kJ ΔH_f^o [H₂O_(g)] = -241.8 kJ ΔH_f^o [C₂H_6(g)] = -84.7 kJ

• 550.647 KJ/mol

• 2855.584 KJ/mol

• -550.647 KJ/mol

• -2855.584 KJ/mol

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

4 NH₃ (g) + 5 O₂ (g) ⟶ 4 NO (g) + 6 H₂O (g)

Using the following information, calculate ΔH for the reaction shown above:

N₂ (g) + O₂ (g) ⟶ 2 NO (g) ΔH = -180.5 kJ

N₂ (g) + 3 H₂ (g) ⟶ 2 NH₃ (g) ΔH = -91.8 kJ

2 H₂ (g) + O₂ (g) ⟶ 2 H₂O (g) ΔH = -483.6 kJ

• 256.0 kJ

• -1628.2 kJ

• -6387 kJ

• None of these

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

A piece of metal with a mass of 32.8 g is heated to 100.5°C and dropped into 138.2 g of water at 20.0°C.  The final temperature of the system is 30.2°C.  What is the specific heat capacity of the metal? (show your work)

• 2.56 J/g°C

• 0.391 J/g°C

• 5.29 J/g°C

• 3.50 J/g°C

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

How much energy must be used to produce 4.75 mol of gaseous water?

H₂O (l) + 44.0 kJ --> H₂O (g)

(Remember, coefficient of 1 = 1 mole)

• 207 kJ

• 9.36 kJ

• 206.8 kJ

• 9.362 kJ

Tags

NGSS.HS-PS1-4

300 mL of water at 95 ºC are added to 700 mL of water at 62.8 ºC. What is the final temperature of the full liter of water?

• 50 ºC

• 85.6 ºC

• 72.5 ºC

• 94.2 ºC

Tags

NGSS.HS-PS3-4

What mass of P₄ must be reacted to produce 5905 kJ of energy?
P₄ + 6Cl₂ --> 4PCl₃ + 2439 kJ

• 25.43 g

• 563.0 g

• 2.421 g

• 300.0 g

Tags

NGSS.HS-PS1-4

An ideal Otto cycle running with air rejects 327 kJ/kg of waste heat each cycle. What is the temperature of the gas before heat rejection if at the end of the heat rejection process the gas is 27C and 95 kPa. Props: Cp=1.005 [kJ/kg K], Cv=0.718 [kJ/kg K], K=1.4, R= 0.287 [kJ/kg K]

• 482 C

• 27 C

• 352 C

• 1461 C

Answer explanation

q = Cv*ΔT allows you to calculate the change in temperature during constant volume heat rejection.

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

750 kJ/kg of heat (q_in) is added to an ideal Otto Cycle after the compression process to the compressed gas (at 689 K, 1745 kPa). What's the temperature of the gas after the heat addition?

Props: Cp=1.005 [kJ/kg K], Cv=0.718 [kJ/kg K], K=1.4, R= 0.287 [kJ/kg K]

• 1435 K

• 1734 K

• 755 K

• 1745 K

Answer explanation

q = Cv ΔT allows you to calculate a temperature change during this constant volume heat addition process.

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

An ideal Otto Cycle with a compression ratio r=8 has 750 kJ/kg of heat addition. What's the net specific work done per cycle?

Props: Cp=1.005 [kJ/kg K], Cv=0.718 [kJ/kg K], K=1.4, R= 0.287 [kJ/kg K]

• 423 kJ/kg

• 41 kJ/kg

• 709 kJ/kg

• 287 kJ/kg

Answer explanation

You can use the compression ratio to calculate the cycle efficiency. From there, q_in * eff_cycle gives you the net work done by the cycle.

Tags

NGSS.HS-PS3-4