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# Assignment Brief</o:p> This assignment is to be completed independently. You will need a periodic table and a calculator.</o:p> LO1 Understand enthalpy changes associated with exothermic...

Assignment Brief

This assignment is to be completed independently. You will need a periodic table and a calculator.

LO1 Understand enthalpy changes associated with exothermic and endothermic reactions

AC 1.1 Interpret enthalpy profile diagrams for exothermic and endothermic reactions including the concept of activation energy, EA

AC 1.2 Define standard conditions and standard enthalpy changes of combustion, formation and reaction.

AC 1.3 Calculate enthalpy changes of reaction from average bond enthalpy values or experimental data

AC 1.4 State Hess’ Law and use enthalpy cycles to indirectly determine enthalpy changes

1. a) Describe the difference between exothermic and endothermic reactions.

b) Define activation energy.

c) Draw a labelled enthalpy profile diagram for an endothermic reaction.

2. a) State the standard conditions used when considering enthalpy changes.

b) Give the notation for and define the following standard enthalpy changes:

i) the standard enthalpy change of formation

ii) the standard enthalpy change of combustion

iii) the standard enthalpy change of reaction.

c) Write equations for the following enthalpy changes:

i) the standard enthalpy change of formation of propan-1-ol, (C3H7OH)

ii) the standard enthalpy change of combustion of propan-1-ol, (C3H7OH)

iii) the standard enthalpy change of formation of water, (H2O)

iv) the standard enthalpy change of combustion of octane, (C8H18)

3. a) Calculate the enthalpy change of combustion of propane (C3H8) using the bond enthalpies below:

 Bond Bond enthalpy(mean value)kJmol-1 C-C 347 C-H 413 O=O 498 C=O 805 O-H 464

b) Calculate the enthalpy change of formation of ammonia (NH3) using the bond enthalpies below:

 Bond Bond enthalpy(mean value)kJmol-1 N≡N 945 H-H 436 N-H 391

4. a) The enthalpy change of combustion of hexane was measured using a calorimeter containing 200 cm3 of water; 0.5g of hexane (C6H14) was burnt. The temperature of the water increased by 28 K.

Calculate the enthalpy change of combustion of hexane.

b) Suggest why this experimental value is less than the standard enthalpy change of combustion of hexane found in a data book.

5. a) State Hess’ law.

b) Use a Hess cycle to calculate the enthalpy change of formation of butane (C4H10) using the data below:

 substance C(s) H2(g) C4H10(g) ∆cHƟ/kJmol-1 -394 -286 -2877

c) Use a Hess cycle to calculate ∆rHƟ for the following reaction using the data provided:

NH3(g) + HCl(g) NH4Cl(s)

 substance NH3)g) HCl(g) NH4Cl(s) ∆fHƟ/kJmol-1 -46 -93 -314

LO2 Understand the factors that affect the rate of a chemical reaction

AC 2.1 Apply the collision theory to explain the factors that affect the rate of a reaction

AC 2.2 Analyse the Maxwell Boltzmann distribution curve to explain the effect of temperature on the rate of a reaction

1. a) Define the term ‘rate of reaction’

b) Apply your understanding of the collision theory to describe and explain the factors that affect the rate of a chemical reaction.

2. Below is a Maxwell Boltzmann distribution curve for a sample of gas at a fixed temperature. EAis the activation energy for the decomposition of this gas.

No. of molecules

with a given energy

energy EA

(a) Copy this diagram and add the distribution curve for the same sample of gas at a higher temperature.

(b) Use the Maxwell-Boltzmann distribution to explain the effect of increasing temperature on the rate of a chemical reaction.

(c) What does the area under the curve represent?

(d) Use your diagram of the Maxwell-Boltzmann distribution to show and explain the effect of adding a catalyst to the rate of a chemical reaction.

LO3- Apply Le Chatelier’s principle to explain the effects of changes in conditions on a system in dynamic equilibrium

AC 3.1 State Le Chatelier’s principle and apply it to explain the effects of changing conditions on the position of equilibrium.

1. a) What does it mean when a system is described as being at dynamic equilibrium?

b) State the conditions needed for a dynamic equilibrium to be established.

c) State Le Chatelier’s Principle

2. The reaction between water and carbon monoxide will reach dynamic equilibrium:

H2O(g) + CO(g) ⇌ H2(g) + CO2(g) ∆H = -42.1 kJ mol-1

Use Le Chatelier’s principle to state and explain the effect on the concentration of hydrogen in the equilibrium mixture if the following changes are made:

i) The concentration of CO(g) is increased

ii) The temperature is decreased

iii) The pressure is increased

3. Use at least one example to explain why, in industrial processes that involve equilibria, a compromise of temperature and pressure conditions is used.

LO4 Understand the theory and reactions of acids and bases

AC 4.1 Define acids and bases using the Bronsted-Lowry theory

AC 4.2 Explain how the pH scale is used to measure acidity and alkalinity

AC 4.3 Explain the reactions of acids with alkalis, a metal and a carbonate

1. a) What are the Bronsted-Lowry definitions of

i) an acid?

ii) a base?

b) What is an alkali?

c) Identify the acids and bases in the following reactions:

i) HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

ii) NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

d) Explain what the pH scale represents and describe how it is used to measure acidity and alkalinity.

e) Use examples to explain the difference between strong and weak acids.

2. Write full chemical equations for the following reactions and describe any changes that you would see:

i) The reaction between nitric acid and aqueous potassium hydroxide.

ii) The reaction between hydrochloric acid and solid calcium carbonate.

iii) The reaction between sulphuric acid and aqueous sodium hydroxide.

iv) The reaction between magnesium and hydrochloric acid.

v) The reaction between hydrochloric acid and ammonia.

vi) The reaction between ethanoic acid and aqueous sodium hydroxide.

vii) The reaction between zinc and nitric acid.

LO5 Understand simple redox processes

AC 5.1 Explain oxidation and reduction in terms of electron transfer and changes in oxidation states.

AC 5.2 Assign oxidation states to atoms in compounds and ions.

1. Define the terms ‘oxidation’ and ‘reduction’ in terms of electron transfer and changes to oxidation states.

2. a) State the oxidation states of all the elements in the following compounds:

i) HCl

ii) H2S

iii) CH4

iv) MgBr2

v) NaClO3

vi) K2SO4

b) State the oxidation states of the elements in the following ions:

i) OH-

ii) CO32-

iii) ClO4-

iv) PO43-

3. a) Define the term ‘redox’

b) Do the following processes involve oxidation, reduction, both oxidation and reduction or

none of these?

i) Mg Mg2+ + 2e-

ii) Zn + Cl2 ZnCl2

iii) Ag+ + Br- AgBr

iv) 2H+ + 2e- H2

4. a) For the following redox reaction identify which element is oxidised, which element is reduced; the oxidising agent and the reducing agent. Include the oxidation states of each atom or ion before and after the reaction.

2Fe + 3Cl2 2FeCl3

b) Balance the two half equations below then combine them to give the overall equation for this reaction, explain why this is a redox reaction.

Zn Zn2+

Cu2+ Cu

Answered 5 days AfterFeb 17, 2022

## Solution

Preeti answered on Feb 22 2022
Assignment Brief
This assignment is to be completed independently. You will need a periodic table and a calculator.
LO1 Understand enthalpy changes associated with exothermic and endothermic reactions
AC 1.1 Interpret enthalpy profile diagrams for exothermic and endothermic reactions including the concept of activation energy, EA
AC 1.2 Define standard conditions and standard enthalpy changes of combustion, formation, and reaction.
AC 1.3 Calculate enthalpy changes of reaction from average bond enthalpy values or experimental data
AC 1.4 State Hess’ Law and use enthalpy cycles to indirectly determine enthalpy changes
1. a) Describe the difference between exothermic and endothermic reactions.

Exothermic Reaction
Endothermic Reaction
1
Exothermic reactions are those reactions in which heat is released to the su
ounding
Endothermic reactions are those reactions in which heat is abso
ed from the su
ounding
2
With the progression of the reaction, temperature is increased.
With the progression of the reaction, temperature is decreased.
3
Enthalpy change is a negative value
Enthalpy change is a positive value
4
Enthalpy of reaction is higher than the product
Enthalpy of reaction is lower than the product
) Define activation energy.
The amount of energy that is required by the compounds to undergo a chemical reaction is called Activation Energy. The activation energy is required by the compound to reach its transition state, where the formation and dissociation of bonds take place. The activation energy is indirectly proportional to rate of reaction i.e., the higher the activation energy, lesser the time required for the reaction to take place.
c) Draw a labelled enthalpy profile diagram for an endothermic reaction.
Products
Potential Energy
ΔH is +ve,
Energy is abso
ed
Process of Reaction
The orange a
ow denotes the activation energy
2. a) State the standard conditions used when considering enthalpy changes.
Following are the standard conditions for enthalpy change:
a) Pressure of 100 kilo Pascal
) Temperature = 298K
c) Both Reactants and products in physical state
d) Solution concentration = 1 mol dm-3
) Give the notation for and define the following standard enthalpy changes:
i) the standard enthalpy change of formation
The standard enthalpy of formation is defined as the amount of enthalpy change during the formation of 1 mole of substance from its pure element under standard conditions.
The standard enthalpy of formation is denoted by ΔH0f.
ii) the standard enthalpy change of combustion
The standard enthalpy of combustion is defined as the amount of enthalpy change during the combustion (burning in the presence of oxygen) of 1 mole of substance under standard conditions. It is denoted by ∆H0c
iii) the standard enthalpy change of reaction.
The standard enthalpy of reaction is defined as the difference between the molar enthalpies of reactants and products, calculated in their standard states. It is denoted by ΔH°r.
c) Write equations for the following enthalpy changes:
i) the standard enthalpy change of formation of propan-1-ol, (C3H7OH)
6 CO2 (g) + 8H2O (l) 2C3H7OH(l) + 9O2(g)
ΔH0f = f (product) - f (reactant )
ΔH0f = {2 ΔH0f (C3H7OH) + 9 ΔH0f (O2)} – {6 ΔH0f (CO2) + 8 ΔH0f (H2O)}
ii) the standard enthalpy change of combustion of propan-1-ol, (C3H7OH)
2C3H7OH(l) + 9O2(g) 6 CO2 (g) + 8H2O (l)
ΔH0c = -c(product) + c (reactant )
ΔH0c = -{6 ΔH0c (CO2) + 8 ΔH0c (H2O)}+{2 ΔH0c (C3H7OH) + 9 ΔH0c (O2)}
iii) the standard enthalpy change of formation of water, (H2O)
2H2(g)+ O2(g) 2H2O (l)
ΔH0f = f (product) - f (reactant )
ΔH0f = 2 ΔH0f (H2O)– {2ΔH0f (H2) + ΔH0f (O2)}
iv) the standard enthalpy change of combustion of octane, (C8H18)
2C8H18 + 25O2 16CO2 + 18 H2O.
ΔH0c = -c(product) + c (reactant )
ΔH0c = -{16ΔH0c (CO2) + 18ΔH0c (H2O)}+{2 ΔH0c (C8H18) + 25ΔH0c (O2)}
3. a) Calculate the enthalpy change of combustion of propane (C3H8) using the bond enthalpies below:

Bond
Bond enthalpy
(mean value)
kJmol-1
C-C
347
C-H
413
O=O
498
C=O
805
O-H
464

C3H8 + 5O2 ---> 3CO2 + 4 H2O
ΔH0c = -c(product) + c (reactant )
c(product) = 3 (2(C=O)) + 4( 2 O-H)
= 6 x 805 + 8 x 464
= 8542
c (reactant ) = 8 x (C-H) + 2 x (C-C) + 5 x (O=O)
= 8 x 413 + 2 x 347 + 5 x 498
=6488
ΔH0c = -8542 + 6488
= - 2054 kJ mol-1
) Calculate the enthalpy change of formation of ammonia (NH3) using the bond enthalpies below:
Bond
Bond enthalpy
(mean value)
kJmol-1
N≡N
945
H-H
436
N-H
391
N2 + 3H2 2NH3
ΔH0f = -f (product) + f (reactant )
N≡N + H-H N-H
f (product) = 2 x3 x 391
= 2346
f...
SOLUTION.PDF