Thermochemistry Assessment

The first law of thermodynamics explains that the change in internal energy (ΔE) of a system is equal to the amount of thermal energy transferred (q) plus the amount of work involved (w)

ΔE = q + w

If a system's internal energy increases by 250 kJ after the addition of 375 kJ of energy as heat, what was the value of the work in the process?

• -625 kJ

• -125 kJ

• 125 kJ

• 625 kJ

Endothermic processes (a)   energy, where exothermic processes (b)   energy.

• absorb
• release

Tags

NGSS.HS-PS1-4

Which of the following is an endothermic reaction?

(A) Ca + H₂O → Ca(OH)₂ + H₂ ΔH = -64.8 kJ/mol

(B) Mg(s) + 1/2 O₂(g) → MgO(s) ΔH = -601.6 kJ/mol

(C) CH₃COOH + NaHCO₃ + 44.4 kJ → CH₃COONa + H₂CO₃

(D) HCl + NaOH → NaCl + H₂O + 55.4 kJ

• A

• B

• C

• D

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

Which of the following is an exothermic process?

• freezing snow

• melting an ice cube

• boiling of water

• a reaction which causes the temperature to decrease

Which of the following absorbs energy during the process/reaction?

• Burning natural gas in a furnace

• Condensing of water vapor to form liquid water

• Liquid water evaporating to form water vapor

• Freezing water on the surface of a lake.

Tags

NGSS.HS-PS3-4

Which of the following has the greatest specific heat?

• iron

• copper

• water

• hydrogen gas

How many kJ of energy are released when 50.0 g of CH₄ combust, given the ΔH_combustion = -891 kJ/mol?

(molar mass of CH₄ = 16.0 g/mol

• 2,780 kJ

• 44,550 kJ

• 2.775 kJ

• 44.550 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

When a 45.0 g sample of an alloy at 100.0^oC is dropped into 100.0 g of water at 25.0^oC, the final temperature is 37.0^oC. What is the specific heat of the alloy?

• 0.423 J⋅g^-1⋅^oC^-1

• 1.77 J⋅g^-1⋅^oC^-1

• 9.88 J⋅g^-1⋅^oC^-1

• 48.8 J⋅g^-1⋅^oC^-1

Tags

NGSS.HS-PS3-4

When a cold block of aluminum at 0^oC is placed in room temperature water at 21^oC in an insulated cup, the water and the aluminum end up at a final temperature of 19^oC. Assuming there was no heat loss to the surroundings, which statement best describes the energy exchanged in this process?

• The block of aluminum released the energy that the water absorbed.

• The block of aluminum absorbed the energy that the water released.

• The block of aluminum absorbed less energy compared to the energy released by the water.

• The block of aluminum absorbed more energy compared to the energy released by the water.

Tags

NGSS.HS-PS3-4

The standard enthalpy of formation, ΔH_f^o, for NO₂(g) is the enthalpy change for which reaction?

(A) N(g) + 2 O(g) → NO₂(g)

(B) 1/2 N₂(g) + O₂(g) → NO₂(g)

(C) 1/2 N₂O₄(g) → NO₂(g)

(D) NO(g) + 1/2 O₂(g) → NO₂(g)

• A

• B

• C

• D

Tags

NGSS.HS-PS1-4