unit 3 - energy changes and rates of reaction chem

define the following and give an example:

a) open system

b) closed system

c) isolated system

a) energy and matter may flow in and out of the system (ex: water bottle with cap removed)

b) energy may enter or leave the system, but not matter (ex: sealed water bottle)

c) ideal system where energy nor matter can move out (ex: oven mitts, sealed water bottle with styrofoam all over it)

Define:

a) exothermic

b) endothermic

a) releases heat

b) absorbs heat

Calculate the heat transferred when 15.0 grams of aluminum undergoes a temperature change from 120°C to 30°C

if:

a) ΔH < 0 → _____________

b) ΔH > 0 → _____________

a) exothermic

b) endothermic

During a combustion experiment, 5 grams of methane (CH₄) produces 277.26 kJ of heat. Calculate the molar enthalpy of methane.

Express the combustion of butane in 4 different ways. Assume ΔH for one mole of butane -2871 kJ/mol

A 10g piece of aluminum, initially 96.0°C, is placed into 500g of water. If the initial temperature of the water was 25.0°C, what was the final temperature of the system?

A 0.100 moles of solid ionic compounds is dissolved into 450g of water. If the water’s temperature increased by 15.0°C, what was the molar enthalpy of the solution?

10.0g of a substance is dissolved in water in a calorimeter. The calorimeter is calibrated and its heat capacity is 550 J/°C. If the temperature change was 27.0°C, what amount of heat was evolved

When heating water on the stove, the heat from the element causes the water to become hotter, until it reaches 100°C. What is this called?

• boiling point of water

Calculate the heat required (in Joules) to change 16g of ice at 0°C to liquid water at 25°C

When white phosphorus burns in air, it produces phosphorus(V) oxide:

P_{4 (s)} + 5 O₂ →P₄O_{10 (s)} ΔH = -2940 kJ

What is the ΔH for the following equation:

P₄O_{10 (s)} →P_{4 (s)} + 5 O₂

• 2940 kJ

Carbon disulfide burns in air, producing carbon dioxide and sulphur dioxide:

CS_{2 (l)} + 3 O_{2 (g)} →CO_{2 (g)} + 2 SO_{2 (g)}  

ΔH = -1075

What is the ΔH for the following equation:

½ CS_{2 (l)} + 3/2 O_{2 (g)} → ½ CO_{2 (g)} + SO_{2 (g)}

• -537.5 kJ

Phosphoric acid, H₃PO₄, can be prepared by the reaction of phosphorus(V) oxide, P₄O₁₀, with water.

¼ P₄O_{10 (s)} + 3/2 H₂O _(l) →H₃PO_{4 (aq)} 

ΔH = -113.2kJ

What is the ΔH for the following equation:

P₄O_{10 (s)} + 6 H₂O _(l) →4 H₃PO_{4 (aq)}

• -452.8 kJ

With platinum catalyst, ammonia will burn in oxygen to give nitric oxide, NO:

4NH_{3 (g)}  + 5 O₂→ 4 NO _(g) + 6 H₂O

ΔH = -906 kJ

What is the ΔH for the following equation:

NO _(g) + 3/2 H₂O _(g) →NH_{3 (g)} + 5/4 O_{2 (g)}

• 226.5 kJ

Hydrogen gas is used as a rocket fuel. The hydrogen is burned in oxygen to produce water vapor:
2 H_{2 (g)} + O₂ →2 H₂O _(g)

ΔH = -484 kJ

What is the enthalpy change for 1.00g of hydrogen?

• -1.20 × 10² kJ/g

Colourless nitric oxide, NO, combines with oxygen to form nitrogen dioxide, NO₂, a brown gas:

2 NO _(g) + O_{2 (g)} →2NO_{2 (g)}

ΔH = -114 kJ

What is the enthalpy change per gram of nitric oxide?

• -1.90kJ/g

Ammonia burns in the presence of a copper catalyst to form nitrogen gas:

4 NH_{3 (g)} + 3 O_{2 (g)} →2 N_{2 (g)}+ 6 H₂O_(g)

ΔH = -1267 kJ

What is the enthalpy change to burn 25.6g of ammonia?

• -476 kJ

Hydrogen sulphide, H₂S, is a foul-smelling gas. It burns to form sulphur dioxide:

2 H₂S _(g) + 3 O_{2 (g)} →2 SO_{2 (g)} + 2 H₂O _(g)

ΔH = -1037 kJ

Calculate the enthalpy change to burn 36.9g of hydrogen sulphide

• -561 kJ

A solid substance has a mass of 0.250kg. It is cooled by 25.0°C and loses 4937.50 J of energy. What is its specific heat capacity? What is the substance?

• 790 J/g°C

Calculate the enthalpy change that occurs when a 10.4g iron nail is hammered into wood, as it changes from 22.0°C to 38.5°C

• 76.2 J

If 0.050kg of ethanol at 15°C gains 1050J of energy, what will be its final temperature?

• 24°C

If some wood gained 4200 J and its temperature went from 25°C to 35°C, what is its mass? 

• 0.24 kg

Aluminum reacts with iron (III) oxide to yield aluminum oxide and iron. The temperature of 1.00kg of water in a calorimeter increases by 3.00°C during the reaction. Calculate the energy released in the reaction

• 12.6kJ

In an experiment, dissolving 2.00g of NaOH in water results in an energy change of 110.4 kJ. What is the molar enthalpy for the process?

• 2.21 × 10³ kJ/mol

Burning 1.5g of methanol results in 3.0 × 10 kJ of energy. What is the molar enthalpy of the reaction?

• 6.4 × 10² kJ/mol

If 1.00 moles of benzene is burned, 3.133 × 10³ kJ is produced. If 5.60g of benzene was burned how much energy will be involved?

• 225kJ

A 24.7g sample of metal is heated to 115°C and then placed in a calorimeter containing 120g of water at a temperature of 23.0°C. After the metal cools, the final temperature of the system is 24.83°C. Assuming no energy is lost, calculate the specific heat capacity of the metal.

• 0.413J/g°C

0.180g piece of magnesium ribbon was placed into 100.0g of hydrochloric acid in a calorimeter, and the temperature changed from 11.20°C to 20.00°C. How much energy was released by the reaction? Assume the specific heat capacity of the acid is the same as that for water

• 3.68kJ

When 15.3g of sodium nitrate were dissolved in 256g of water in a calorimeter, the temperature fell from 25.00°C to 21.56°C. What is the enthalpy change for the reaction?

• 3.68 kJ

When 21.5g of KNO₃ were dissolved in water in a calorimeter, the temperature fell from 25.00°C to 14.14°C. The heat capacity of the calorimeter and its contents is 682 J/°C. What was the amount of energy involved in the reaction? 

• 7.41 kJ

When 23.6g of calcium chloride was dissolved in water in a calorimeter, the temperature rose from 25.0°C to 38.7°C. If the heat capacity of the solution and the calorimeter is 1258 J/°C, what is the enthalpy change of the reaction? 

• -17.2 kJ

A 2.84g sample of ethanol was burned completely in a bomb calorimeter (used to measure heat for reactions involving gases). The temperature of the calorimeter rose from 25.0°C to 33.7°C. If the heat capacity of the calorimeter and contents was 9.63 kJ/°C, what is the ΔH value when 1.00 mol of ethanol is burned? Write your answer as a thermochemical equation

The reaction is:
C₂H₅OH _(l) + 3 O_{2 (g)} → 2 CO_{2 (g)} + 3 H₂O _(l)

• ΔH_comb = -1.36 × 10³ kJ

A 3.51g sample of benzene was burned in a bomb calorimeter. The temperature of the calorimeter rose from 25.0°C to 37.2°C. If the heat capacity of the calorimeter and its contents was 12.05 kJ/°C, what is the ΔH for burning 1.00 mol of benzene? Write your answer as a thermochemical equation

• ΔH_comb = -3.27 × 10³ kJ

A 6.48g sample of LiOH was dissolved in water in a calorimeter. The temperature of the calorimeter rose from 25.0°C to 36.7°C. The heat capacity of the calorimeter and its contents is 547 J/°C. What is the ΔH for the solution process if 3.50mol was dissolved?

• ΔH = -82.8 kJ

Given the following two equations:

2 Al_(s) + 3/2 O_{2 (g)} → Al₂O₃   ΔH= -1676 kJ

Mn _(s) + O_{2 (g)} → MnO_{2 (s)}   ΔH= -521

Calculate ΔH for the reaction:

4 Al _(s) + 3 MnO_{2 (s)} →2 Al₂O_{3 (s)} + 3 Mn _(s)

ΔH = -1789 kJ

Given the following two equations:

H₂O_{2 (l)} →H₂O + ½ O₂ ΔH= -98.0 kJ

2 H_{2 (g)} + O₂ →2 H₂O   ΔH= -571.6 kJ

Calculate the ΔH for the reaction:

H₂ + O₂ → H₂O₂ 

ΔH = -187.8 kJ

Given the following equations:

N₂H₄ + O₂ → N₂ + 2 H₂O  ΔH= -622.2 kJ

H₂ + ½ O₂ → H₂O              ΔH= -285.8 kJ

Calculate ΔH for the reaction:

N₂ + 2 H₂ → N₂H₄

ΔH = 50.6 kJ

Given the following three equations:

2 W + 3 O₂ →2 WO₃  ΔH= -1680.6 kJ

C + O₂ →CO₂            ΔH= -393.5 kJ

2 WC + 5 O₂ →2 WO₃ + 2 CO₂ ΔH= -2391.6 kJ

Calculate ΔH for the reaction:

W + C → WC   

ΔH = -38.0 kJ

Given the following three equations:

2 NH₃ →N₂ + 3 H₂ ΔH = 46.0 kJ

2 NO₂ + 7 H₂ → 2 NH₃ + 4 H₂O ΔH= 57.0kJ

2 NO₂ → N₂ + 2 O₂ ΔH = 16.5 kJ

Calculate ΔH for the reaction:

H₂ + ½ O₂ → H₂O

ΔH= 21.625 kJ

Given the following three equations:

CO₂ →C + O₂ ΔH= 295.1 kJ

H₂O → H₂ + ½ O₂ ΔH= 214.3 kJ

CH₄ → C + 2 H₂ ΔH= 56.1 kJ

Calculate ΔH for the reaction:

CO₂ + 2 H₂O →CH₄ + 2 O₂

ΔH = 667.6 kJ

Find the enthalpy change for the formation of 1 mole of butane. You are given the following information:

(I) 2 C₄H₁₀ + 13 O₂ → 8 CO₂ + 10 H₂O

ΔH = -5314.8 kJ

(II) C + O₂ → CO₂ ΔH = -393.5 kJ

(III) 2 H₂ + O₂ → 2 H₂O ΔH = -483.6 kJ

In other words, find ΔH using Hess’s Law when butane is formed from its elements

What process is it

• 4 C + 5 H₂ →C₄H₁₀

• ΔH = -125.6 kJ

• exothermic

Calculate the amount of heat needed to just melt 40.0g of ice at 0°C

• 13.4kJ

How much heat is required to change 50.0g of water at 100°C to steam at 100°C?

• 113 kJ

Calculate the enthalpy change when 500g of steam at 100°C condenses and cools to 25.0°C

• -1.29 × 10³ kJ

Calculate the amount of heat needed to change 0.20kg of ice at -10.0°C to water at 20.0°C

• 88 kJ

Calculate the amount of heat needed to convert 0.100kg of ice at -5.00°C to steam at 110.0°C

• 305 kJ

Using bond energies, calculate ΔH for each chemical reaction. Watch out for multiple bonds. Show ur work

2 CH₃OH + 3 O₂ → 2 CO₂ + 4 H₂O

• -1286 kJ

Using bond energies, calculate ΔH for each chemical reaction. Watch out for multiple bonds. Show ur work

C₂H₅OH + 3 O₂ → 2 CO₂ + 3 H₂O

• -1250 kJ

Using bond energies, calculate ΔH for each chemical reaction. Watch out for multiple bonds. Show ur work

C₂H₄ + HBr →C₂H₅Br

• -56 kJ

Using bond energies, calculate ΔH for each chemical reaction. Watch out for multiple bonds. Show ur work

C₂H₄ + H₂O → C₂H₅OH

• -41 kJ

Using bond energies, calculate ΔH for each chemical reaction. Watch out for multiple bonds. Show ur work

H₂ + O₂ → H₂O₂

• -134 kJ

Using bond energies, calculate ΔH for each chemical reaction. Watch out for multiple bonds. Show ur work

2 H₂ + N₂ → N₂H₄

• 95 kJ

Using bond energies, calculate ΔH for each chemical reaction. Watch out for multiple bonds. Show ur work

N₂F₂ + F₂ → N₂F₄

• -160 kJ

Using bond energies, calculate ΔH for each chemical reaction. Watch out for multiple bonds. Show ur work

HCN + 2 H₂ →CH₃NH₂

• -148 kJ

What is the standard heat of reaction when carbon tetrachloride, CCl₄, condenses

• -43 kJ

Calculate the standard heat of reaction as methanol evaporates

• 38.1 kJ

Calculate the standard heat of reaction for the following reaction:

2 H₂S_(g) + 3 O_2(g) →2 H₂O_(l) + 2 SO_2(g)

• -1124 kJ

Carbon disulfide is a colourless liquid. When pure, it is nearly oudourless, but the commercial product smells vile. Carbon disulfide is used in the manufacture of rayon and cellophane:

CS_2(l) + 3 O_2(g) → CO_2(g) + 2 SO_2(g)

• -1076.1 kJ

The first step in the preparation of lead from its ore consists of resting the ore:

2 PbS_(s) + 3 O_2(g) → 2 SO_2(g) + 2 PbO_(s)

calculate the standard heat of reaction

• -835 kJ

Iron is obtained from iron ore by reduction with carbon monoxide:

Fe₂O_3(s) + 3 CO_(g) → 2 Fe_(s) + 3 CO_2(g)

Calculate the standard enthalpy change for the reaction

• -24.8 kJ

why is water a good cooking substance in related to specific heat capacity?

• takes longer to get rid of heat since it takes long to boil

Why does pavement (concrete) heat up fast and cool down fast

• its specific heat capacity is low so it heats up faster and cools down faster

what are the types of chemical systems

• open

• closed

• isolated

what are the types of thermal energy

• endothermic → absorbsheat (+)

• exothermic → releases heat (-)

• -5.17 × 10^-6 mol/L.s

• -1.13 × 10^-4 mol/L.s

• a) -0.0227 mol/L.hr

• b) 0.0453 mol/L.hr

• a) -2.370 × 10^-3 mol/L.min

• b) 1.185 × 10^-3 mol/L.min

- State the rate law and state the reaction order for each reactant

- calculate the rate constant (include units)

- finish with a statement

- State the rate law and state the reaction order for each reactant

- calculate the rate constant (include units)

- finish with a statement

- State the rate law and state the reaction order for each reactant

- calculate the rate constant (include units)

- finish with a statement

- State the rate law and state the reaction order for each reactant

- calculate the rate constant (include units)

- finish with a statement

- State the rate law and state the reaction order for each reactant

- calculate the rate constant (include units)

- finish with a statement

What does the first law of thermodynamics state

• total energy of the universe is constant

• energy cannot be created or destroyed

• energy can only be transferred into different forms

what is the second law of thermodynamics state

• also known as law of entropy →chaos/disorder

• all changes, whether it be direct or indirect, increases the entropy of the universe

What are the five ways that a system will experience an increase in entropy

• increase in volume of a gaseous system

• increase of temp of a  system

• when there is a state change from solid to liquid to gas

• when there are more moles of products then of reactants in a system

• complex molecules break down into simpler ones

What are the ways we can determine if a reaction is spontaneous or not

• ΔH < 0 and ΔS > 0 it is spontaneous

• ΔH > 0 and ΔS < 0 it is not spontaneous

• if ΔH < 0 and ΔS < 0 then it depends on temp

• if ΔH > 0 and ΔS > 0 then it depends on temp

  • ΔG = ΔH - TΔS

  • If ΔG = 0 =, it is at equilibrium (phase change)

  • if ΔG < 0, it is spontaneous towards the forward reaction

  • if ΔG > 0, it is not spontaneous, or it is spontaneous towards the reverse reaction