For which of these processes is the value of ΔH expected to be negative?

1. The temperature increases when calcium chloride dissolves in water.

2. Steam condenses to liquid water

3. Water boils

4. Dry ice sublimates

What factors determine the spontaneity of a reaction?

When liquid condenses, what are the signs for Δ H and Δ S ?

What signs of Δ H and Δ S will always yield a reaction that is non-spontaneous ? (Think of the equation for ΔG°!!)

Predict the signs of Δ H , Δ S and Δ G for the reaction:

Mg(s) → Mg(g)

Calculate ΔH° for the combustion of methane.

CH₄ (g) + 2 O₂ (g) → CO₂ (g) + 2 H₂O (g)

Given the enthalpies of formation below.

CH₄ (g): -50.8 kJ/mol

O₂ (g): 0 kJ/mol

CO₂ (g): -394.4 kJ/mol

H₂O (g): -228.57 kJ/mol

A reaction has a negative ΔH and a positive ΔS. Which of the following is true?

The formation ½ A2 + 2 B2 + C --> CAB4 has an enthalpy of formation of -104 kJ and a change in entropy of -60.8 J/K at 30 °C. What is the free energy and spontaneity of the reaction?

At what temperature will a reaction become spontaneous is the change in enthalpy is -192 KJ/mol and the change in entropy is -562 J/mol?

Calculate the entropy change for the reaction

C₃H₈(g) + 5O₂(g)=> 3CO₂(g) +4H₂O(g)

Given the entropies below

C₃H₈(g) =270J/mol.K

O₂(g)= 205 J/mol.K

CO₂(g)=214 J/mol.K

H₂O(g)=70 J/mol.K

The standard enthalpy changes of formation of iron(II) oxide, FeO(s), and aluminium oxide, Al₂O₃(s), are –266 kJ mol^–1and –1676 kJ mol^–1 respectively.

What is the enthalpy change under standard conditions for the following reaction?

3FeO(s) + 2Al (s)  -> 3Fe(s) + Al₂O₃(s)

The enthalpies of combustion of C(s), H2(g) and C4H9OH(l) (in kJmol^-1) are as follows

C(s) + O₂(g) -> CO₂(g) ∆H=-393kJ/mol

H₂(g) + ½O₂(g) -> H₂O(l) ∆H=-286kJ/mol

C₄H₉OH(l) + 6O₂(g) -> 4CO₂(g) + 5H₂O(l) ∆H=-1371kJ/mol

What is the enthalpy change for the reaction shown below?

4C(g) + 5H₂(l) + ½O₂(g) -> C₄H₉OH(l)

What is the relationship between enthalpies p, q, r and s?

S(s) + H₂(g) -> H₂S(g) ∆H=p

H₂(g) + ½O₂(g) -> H₂O(l) ∆H=q

S(s) + O₂(g) -> SO₂(g) ∆H=r

H₂S(g) + 1½O₂(g) -> H₂O(l) + SO₂(g) ∆H=s

The enthalpy change for the reaction

C(s, graphite) + 1⁄2O₂(g) --> CO(g) cannot be measured directly since some carbon dioxide is always formed in the reaction.

It can be calculated using Hess’s Law and the enthalpy changes of combustion of graphite and of carbon monoxide.

C(s, graphite) + O₂(g) --> CO₂ ΔH=-394 kJmol^–1

CO(g) + 1⁄2O₂(g) --> CO₂ ΔH=-283 kJmol^–1

The enthalpy change for the reaction of graphite with oxygen to give carbon monoxide is

The average bond enthalpies for O-O and O=O are 146kJ/mol and 496kJ/mol respectively. Calculate the enthalpy change for the reaction shown.

H-O-O-H =H20 +1/2O2

The average bond enthalpies for O-O and O=O are 146kJ/mol and 496kJ/mol respectively. Calculate the enthalpy change for the reaction shown.

H-O-O-H =H20 +1/2O2

1. The enthalpy change for the reaction, ∆H_r , is equal to

The average bond enthalpy for the C-H bond is 412kJ/mol. which process has an enthalpy change closest to this value?

Given the following data: ΔH^○_f[FeO(s)] = –270kJmol^–1

ΔH^○_f [Fe₂O₃(s)] = –820 kJ mol^–1

Select the expression which gives the enthalpy change, in kJ mol^–1, for the reaction:

2FeO(s) + 1⁄2O₂(g) → Fe₂O₃(s)

MgCl₂(s) ---> Mg²⁺(g) + 2Cl^-(g)

This equation represents