Thermochem - Hess and dHf

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-PS1-4

Consider the following equations.

Mg_(s) + O_2(g) → MgO_(s) ∆H = –602 kJ

H_2(g) + O_2(g) → H₂O_(g) ∆H = –242 kJ

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

MgO_(s) + H_2(g) → Mg_(s) + H₂O_(g)

• -844

• -360

• +360

• +844

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

In an endothermic reaction the system is releasing energy.

• True
• False
• Sometimes

Use the formation data below to 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

The standard enthalpy changes of formation of carbon dioxide and of methanoic acid are −394 kJ/mol and −409 kJ/mol respectively. Calculate ΔH for the reaction

H_{2 (g)} + CO_{2 (g)} → HCOOH _(l)

• −803 kJ/mol

• −15 kJ/mol

• +803 kJ/mol

• +15 kJ/mol

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Which of these has a ΔH^o_f value that is NOT zero?

• F₂(g)

• Br₂(g)

• I₂(s)

• C(s, graphite)

Tags

NGSS.HS-PS1-4

Which of the following has a ΔH_f^o value of 0?

• Fe₂(g)

• H₂O(g)

• CO(g)

• N₂(g)

If the sum of the enthalpy of formation for products is 400 kJ and reactants is 220 kJ. What is the overall enthalpy of reaction?

• 620 kJ

• 280 kJ

• 180 kJ

• -120 kJ

The ΔH for 2Na + Cl₂ → 2NaCl is -35 kJ. What is ΔH for the reverse reaction?

• - 35 kJ

• 35 kJ

• 70 kJ

• - 70 kJ

Tags

NGSS.HS-PS1-4

Given samples of the same size and same starting temperature, if 100 J of energy is applied, which will have the greatest temperature change?

• Iron

• Aluminum

• Zinc

• Steel

• Tin