hess's law

Using the equations below:

C(s) + O₂(g) → CO₂(g) ∆H = –390 kJ

Mn(s) + O₂(g) → MnO₂(s) ∆H = –520 kJ

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

MnO₂(s) + C(s) → Mn_(s) + CO₂(g)

• 910

• 130

• -130

• -910

Using the equations below

Cu(s) + ¹/₂O₂(g) → CuO(s) ∆H = –156 kJ

2Cu(s) + O₂(g) → Cu₂O(s) ∆H = –170 kJ

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

2CuO(s) → Cu₂O(s) + ¹/₂O₂(g)

• 142

• 15

• -15

• -142

Consider the following equations.

Mg(s) + O₂(g) → MgO(s) ∆H = –602 kJ

H₂(g) + O₂(g) → H₂O(g) ∆H = –242 kJ

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

MgO(s) + H₂(g₎ → Mg(s) + H₂O(g)

• -844

• -360

• +360

• +844

The following equations show the oxidation of carbon and carbon monoxide to carbon dioxide.

C(s) +O₂(g) → CO₂(g) ΔH = –x kJ mol^–1

CO(g) + O₂(g) → CO₂(g) ΔH = –y kJ mol^–1

What is the enthalpy change, in kJ mol^–1, for the oxidation of carbon to carbon monoxide?

C(s) + O₂(g) → CO(g)

• x + y

• -x - y

• y - x

• x - y

The standard enthalpy change of formation values of two oxides of phosphorus are:

P₄(s) + 3O₂(g₎ → P₄O₆(s) ΔH_f = –1600 kJ mol^–1

P₄(s) + 5O₂(g) → P₄O₁₀(s) ΔH_f = –3000 kJ mol^–1

What is the enthalpy change, in kJ mol^–1, for the reaction below?

P₄O_6(s) + 2O₂(g) → P₄O₁₀(s)

• +4600

• +1400

• –1400

• –4600

In an endothermic reaction the system is releasing energy.

• True
• False
• Sometimes

In an exothermic reaction, heat is ...

• taken in
• given out
• nothing happens
• it gets colder

A chemical reaction that requires energy is a(n)

• exothermic reaction 
• endothermic reaction 
• over reaction 
• redox reaction

• 86 kJ

• - 86 kJ

• 68 kJ

• -68 kJ

• -233
• -11.3
• -805
• -226