What is the sign of ΔE_system if energy flows from the surroundings into a chemical system?

A gas absorbs 62 kJ of heat and does 48 kJ of work. Calculate ΔE.

Calculate the change in internal energy of the system if it releases 415 kJ of heat and does 562 kJ of work on the surroundings.

Calculate ΔE for each of the following.

a) q = -62 kJ, w = +59 kJ

b) q = +48 kJ, w = –56 kJ

c) q = -92 kJ, w = 0 kJ

The gas in a piston is heated up by absorbing 984 J of heat and expands performing 541 J of work on the surroundings.

What is the change in internal energy for the system (the gas)?

A pump is held under 1.30 atm external pressure. How much work (in J) is required to expand its volume from 1.80 L to 3.50 L?

A balloon filled with 8.50 moles of nitrogen at 23.0 ^oC expands from 3.54 L to 5.64 L by increasing its temperature to 58.0 ^oC under constant pressure of 1.10 atm. Calculate q, w, and ΔE in kJ for the nitrogen gas in the balloon if its heat capacity is 29.15 J/°C · mol.

How much heat in kJ is required to warm 1.50 L of water from 25.0 ^oC to 100.0 °C? (Assume a density of 1.0 g/mL for the water.)

What is the final temperature when a 40 g sample of water at 90 °C is mixed with a 60 g sample at 25 °C?

How much heat does it take to increase the temperature of a 540.6-g sample of Fe from 20.0 °C to 84.3 °C? The specific heat of iron = 0.450 J/g °C.

Calculate the specific heat capacity of a metal if a 17.0 g sample requires 481 J to change the temperature of the metal from 25.0 °C to 67.0 °C?

Calculate the energy of combustion for one mole of butane if burning a 0.367 g sample of butane (C₄H₁₀) has increased the temperature of a bomb calorimeter by 7.73 °C. The heat capacity of the bomb calorimeter is 2.36 kJ/ °C.

How many joules of energy is required to melt 40.0 g of ice at 0 °C? The heat of fusion (ΔH_fus) for ice is 334.0 J/g.

How many kJ of energy does it take to change 36.0 g of ice at -15.0 °C to water at 0. °C ? The specific heat of ice is 2.10 J/g°C and the heat of fusion (ΔH_fus) for ice is 334.0 J/g. Ignore the significant figures for this problem.

The enthalpy change for the reaction is given below:

2CH₃OH(l) + 3O₂(g) → 4H₂O(l) + 2CO₂(g) ΔH = -1452.8 kJ

a) What quantity of heat is released for each mole of water formed?

b) What quantity of heat is released for each mole of oxygen reacted?

How much heat will be released if 44.8 g of SO₂ is reacted with an excess of oxygen according to the following chemical equation?

2SO2(g) + O₂(g) → 2SO₃(g), ΔH° = –198 kJ

What is ΔH° for the following reaction

2C₆H₆(l) + 15O₂(g) → 12CO₂(g) + 6H₂O(l), ΔH° = ? kJ

if the consumption of 27.3 g of benzene (C₆H₆) produces 1144 kJ of heat?

Based on the heat of reaction for the chlorination of methane, how much heat will be released if 233.6 grams of hydrochloric acid are formed?

CH₄(g) + 3Cl₂(g) → CHCl₃(l) + 3HCl(g), ΔH° = -334 kJ

Calculate how many kJ of heat-energy will be released when 12.65 g of magnesium carbonate reacts with 650. mL of 0.400 M hydrochloric acid?

MgCO₃(s) + 2HCl(aq)  →  MgCl₂(aq) + H₂O(l) + CO₂(g), ΔH° = –112 kJ

Using the standard heats of formation given below, calculate the heat of reaction for the combustion of ammonia:

4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g), ΔH°_rxn = ?

ΔH_f° for NH₃(g) = –46.2 kJ/mol
ΔH_f° for NO(g) = 90.4 kJ/mol
ΔH_f° for H₂O(g) = –241.8 kJ/mol

Combustion of butane (C₄H₁₀) releases 5755 kJ of energy according to the following chemical equation.

2C₄H₁₀(g) + 13O₂(g) → 8CO₂(g) + 10H₂O(l), ΔH°_rxn = -5755 kJ

Calculate the molar enthalpy of formation of butane using the information given below:

ΔH_f° for CO₂(g) = –393.5 kJ/mol
ΔH_f° for H₂O(l) = –285.8 kJ/mol

Zinc is recovered from ZnS by first oxidizing it to ZnO. Calculate the enthalpy of this oxidation reaction using the data given below:

2ZnS(s) + 3O₂(g) → 2ZnO(s) + 2SO₂(g)

ΔH_f° for SO₂(g) = -296.8 kJ/mol
ΔH_f° for ZnS(s) = -206.0 kJ/mol
ΔH_f° for ZnO(s) = -350.5 kJ/mol

Using the standard heats of formation given below, calculate the heat of reaction between barium carbonate (BaCO₃) and sulfuric acid (H₂SO₄).

BaCO₃(s) +  H₂SO₄(aq) → BaSO₄(s) + CO₂(g) + H₂O(l)

ΔH_f° for BaSO₄(s) = -1473.2 kJ/mol
ΔH_f° for CO₂(g) = –393.5 kJ/mol
ΔH_f° for H₂O(l) = –285.8 kJ/mol
ΔH_f° for BaCO₃(s) = -1213.0 kJ/mol
ΔH_f° for H₂SO₄(aq) = -814.0kJ/mol

The heat of reaction for the reaction of nitrogen oxide and chlorine is –76 kJ:

2NO(g) + Cl₂(g) ⇆ 2NOCl(g)

What is the enthalpy change for the following reaction?

2NOCl(g) ⇆ 2NO(g) + Cl₂(g)

The heat of reaction for the oxidation of hydrogen sulfide to sulfur dioxide accord according to the following equation is -1036 kJ:

2H₂S(g) + 3O₂(g) → 2SO₂(g) + 2H₂O(g)

What is the enthalpy change for the following reaction?

H₂S(g) + 1.5O₂(g) → SO₂(g) + H₂O(g)

Consider the thermochemical equation for the combustion of nitromethane (CH₃NO₂):

2CH₃NO₂(l) + 3/2O₂(g) → 2CO₂(g) + 3H₂O(l) + N₂(g), ΔH °_rxn = -1418 kJ

 What is the enthalpy change for this reaction represented by the following equation?

 4CH₃NO₂(l) + 3O₂(g) → 4CO₂(g) + 6H₂O(l) + N₂(g), ΔH °_rxn = ?

Using the Hess’s law, calculate ΔH^o for the reaction:

2NO₂ + Cl₂(g) → 2NOCl(g) + O₂(g), ΔH^o = ?

Use the following reactions and given ΔH’s:

1) 2NO(g) + Cl₂(g) → 2NOCl(g), ΔH^o = -76 kJ

2) 2NO(g) + O₂(g) → 2NO₂(g), ΔH^o = -114 kJ

Calculate the enthalpy for the oxidation of CO to CO₂ using the enthalpy of reaction for the combustion of C to CO (ΔH = -221.0 kJ) and the enthalpy for the combustion of C to CO₂ (ΔH = -393.5 kJ).

2CO(g) + O₂(g)  →  2CO₂(g)  ΔH = ?

1) C(s) + O₂(g)  →  CO₂(g)  ΔH = -393.5 kJ

2) 2C(s) + O₂(g)  →  2CO(g)  ΔH = -221.0 kJ

Calculate the enthalpy for the combustion reaction of sulfur to sulfur trioxide using the enthalpies of the two reactions shown below:

2S(s) + 3O₂(g)  →  2SO₃(g)  ΔH = ?

1) S(s) + O₂(g)  →  SO₂(g)  ΔH = -297 kJ

2) 2SO₃(g)  → 2SO₂(g) + O₂(g)  ΔH = 198 kJ

Using the Hess’s law, calculate ΔH^o for the combustion reaction of butene:

C₄H₈(g) + 6O₂(g) → 4CO₂(g) + 4H₂O(l), ΔH^o = ?

Use the following reactions and given ΔH’s:

1) 2H₂(g) + O₂(g) → 2H₂O(g), ΔH^o = -571 kJ

2) C₄H₈(g) + H₂(g) → C₄H₁₀(g), ΔH^o = -126 kJ

3) 2C₄H₁₀(g) + 13O₂(g) → 8CO₂(g) + 10H₂O(l), ΔH^o = -5754 kJ

Using the Hess’s law and the enthalpies of the three combustion reactions below, calculate the enthalpy of the reaction producing methanol (CH₃OH) from carbon monoxide and hydrogen gas.

CO(g) + 2H₂(g) → CH₃OH(g), ΔH = ?

1) 2CO(g) + O₂(g) → 2CO₂(g), ΔH = -566 kJ

2) 2H₂(g) + O₂(g) → 2H₂O(g), ΔH^o = -571 kJ

3) 2CH₃OH(g) + 3O₂(g) → 2CO₂(g) + 4H₂O(g), ΔH^o = −1430 kJ

Using the Hess’s law and the enthalpies of the given reactions, calculate the enthalpy of the combustion reaction of CH₃Cl:

CH₃Cl(g) + O₂(g) → CO(g) + HCl(g) + H₂O(l), ΔH = ?

1) CO(g) + 2H₂(g) → CH₃OH(g), ΔH^o = -139 kJ

2) 2H₂(g) + O₂(g) → 2H₂O(g), ΔH^o = -571 kJ

3) CH₃OH(g) + HCl(aq) → CH₃Cl(g) + H₂O(l), ΔH^o = -28 kJ

Using the Hess’s law and the enthalpies of the given reactions, calculate the enthalpy of the following oxidation reaction of ammonia:

4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g), ΔH = ?

1) N₂(g) + 3H₂(g) → 2NH₃(g), ΔH = -92 kJ

2) 2H₂(g) + O₂(g) → 2H₂O(g), ΔH = -484 kJ

3) N₂(g) + O₂(g) → 2NO(g), ΔH = 181 kJ

Using the Hess’s law and the enthalpies of the given reactions, calculate the enthalpy of the following oxidation reaction between CuO and HCl:

2CuO(s) + 4HCl(g) → 2CuCl(s) + Cl₂(g) + 2H₂O(g), ΔH = ?

1) CuO(s) + H₂(g) → Cu(s) + H₂O(g), ΔH = -85 kJ

2) 2Cu(s) + Cl₂(g) → 2CuCl(s), ΔH = -274 kJ

3) H₂(g) + Cl₂(g) → 2HCl(g), ΔH = -184 kJ