Hess's Law

Using the equations below:

C_(s) + O_2(g) → CO_2(g) ∆H = –390 kJ
Mn_(s) + O_2(g) → MnO_2(s) ∆H = –520 kJ

what is ∆H (in kJ) for the following reaction?

MnO_2(s) + C_(s) → Mn_(s) + CO_2(g)

• 910

• 130

• -130

• -910

Tags

NGSS.HS-PS3-1

What is the Delta H if you reverse the reaction.

• 86 kJ

• - 86 kJ

• 68 kJ

• -68 kJ

Tags

NGSS.HS-PS1-4

Which statements about Hess's law are correct?

• I and II only

• I, II, and III

• I and III only

• II and III only

Tags

NGSS.HS-PS1-4

The energy cycle shows how Hess's Law can be used to find the standard enthalpy of formation of methane if the enthalpies of combustion of carbon, hydrogen and methane are known. Which expression will give the correct value for the enthalpy of formation of methane?

• ΔH_c^⦵(methane) + ΔH_c^⦵(carbon) + ΔH_c^⦵(hydrogen)

• ΔH_c^⦵ (carbon) + 2ΔH_c^⦵ (hydrogen) − ΔH_c^⦵(methane)

• ΔH_c^⦵(methane) − ΔH_c^⦵(carbon) + 2ΔH_c^⦵(hydrogen)

• ΔH_c^⦵(carbon) + 2ΔH_c^⦵(hydrogen) + ΔH_c^⦵(methane)

Tags

NGSS.HS-PS1-4

The ore magnetite, Fe₃O₄, can be reduced by carbon monoxide

Fe₃O_4(s) + 4CO_(g) → 3Fe_(s) + 4CO_2(g)

The standard enthalpies of formation of magnetite, carbon monoxide, and carbon dioxide are −1118, −110, and −394 kJ mol−1 respectively.

What is the standard enthalpy change for the reduction of magnetite by carbon monoxide?

• + 3134 kJ

• - 18kJ

• +18 kJ

• _3134 kJ

Tags

NGSS.HS-PS1-4

Ethanol can be oxidized to ethanal,

C₂H₅OH_(l) + ½O_2(g) → CH₃CHO_(l) + H₂O_(l) ΔH^⦵ = a

which can then be further oxidized to ethanoic acid.

CH₃CHO_(l) + ½O_2(g) → CH₃COOH_(l) ΔH^⦵ = b

Ethanol can also be oxidized directly to ethanoic acid

C₂H₅OH_(l) + O_2(g) → CH₃COOH_(l) + H₂O_(l) ΔH^⦵ = c

Which is the correct relationship between a, b and c?

• a = b - c

• c = a - b

• b = a - c

• b = c- a

Tags

NGSS.HS-PS3-1

Using the equations below: \( \text{C}_{(s)} + \text{O}_2{(g)} \rightarrow \text{CO}_2{(g)} \) \( \Delta H = -390 \text{kJ} \) \( \text{Mn}_{(s)} + \text{O}_2{(g)} \rightarrow \text{MnO}_2{(s)} \) \( \Delta H = -520 \text{kJ} \) what is \( \Delta H \) (in kJ) for the following reaction? \( \text{MnO}_2{(s)} + \text{C}_{(s)} \rightarrow \text{Mn}_{(s)} + \text{CO}_2{(g)} \)

• 910

• 130

• -130

• -910

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Which statements about Hess's law are correct?

• I and II only

• I, II, and III

• I and III only

• II and III only

Tags

NGSS.HS-PS1-4

The ore magnetite, \( \text{Fe}_3\text{O}_4 \), can be reduced by carbon monoxide \( \text{Fe}_3\text{O}_4{(s)} + 4\text{CO}_{(g)} \rightarrow 3\text{Fe}_{(s)} + 4\text{CO}_2{(g)} \) The standard enthalpies of formation of magnetite, carbon monoxide, and carbon dioxide are \(-1118, -110,\) and \(-394 \text{kJ mol}^{-1}\) respectively. What is the standard enthalpy change for the reduction of magnetite by carbon monoxide?

• + 3134 kJ

• - 18kJ

• +18 kJ

• _3134 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Ethanol can be oxidized to ethanal, \( \text{C}_2\text{H}_5\text{OH}_{(l)} + \frac{1}{2}\text{O}_2{(g)} \rightarrow \text{CH}_3\text{CHO}_{(l)} + \text{H}_2\text{O}_{(l)} \) \( \Delta H^\circ = a \) which can then be further oxidized to ethanoic acid. \( \text{CH}_3\text{CHO}_{(l)} + \frac{1}{2}\text{O}_2{(g)} \rightarrow \text{CH}_3\text{COOH}_{(l)} \) \( \Delta H^\circ = b \) Ethanol can also be oxidized directly to ethanoic acid \( \text{C}_2\text{H}_5\text{OH}_{(l)} + \text{O}_2{(g)} \rightarrow \text{CH}_3\text{COOH}_{(l)} + \text{H}_2\text{O}_{(l)} \) \( \Delta H^\circ = c \) Which is the correct relationship between \( a, b \) and \( c \)?

• a = b - c

• c = a - b

• b = a - c

• b = c- a

Tags

NGSS.HS-PS1-4