Hess’ law also known as Hess’s law of constant heat summation states, “at constant temperature, heat energy changes ( ∆ H r ) accompanying a chemical reaction will remain constant, irrespective of the way the reactants react to form product”. The first law of thermodynamics states that the total energy of the substances before and after any (physical or chemical) change should be equal. According to the law, the total energy of the reactant should be equal to the total energy of the product. Any difference in the energy between the reactants and products is also fixed at a particular temperature and will not change with the path followed by the reactants to form products. Hence, heat energy also can be considered as a reactant or product of the reaction and included in the reaction. Hence, exothermic reactions can be written as: A + B → C + D + ∆ H Similarly, endothermic reactions become: A + B + ∆ H → C + D

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>BEFORE YOU START

Lawrie Ryan and Roger Norris Solutions for Chapter: Lattice Energy, Exercise 1: BEFORE YOU START

Author:Lawrie Ryan & Roger Norris

Lawrie Ryan Chemistry Solutions for Exercise - Lawrie Ryan and Roger Norris Solutions for Chapter: Lattice Energy, Exercise 1: BEFORE YOU START

Attempt the free practice questions on Chapter 19: Lattice Energy, Exercise 1: BEFORE YOU START with hints and solutions to strengthen your understanding. Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years) solutions are prepared by Experienced Embibe Experts.

Questions from Lawrie Ryan and Roger Norris Solutions for Chapter: Lattice Energy, Exercise 1: BEFORE YOU START with Hints & Solutions

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>BEFORE YOU START>Q 1

Draw a fully labelled reaction pathway diagram (energy profile diagram) for an endothermic reaction. Explain, how this diagram shows that the reaction is endothermic?

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>BEFORE YOU START>Q 3

Define the terms crystal lattice, bond energy, enthalpy change, activation energy, standard conditions, standard enthalpy change of formation.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>BEFORE YOU START>Q 4

Write the equation which represents the enthalpy change of formation of calcium carbonate.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>BEFORE YOU START>Q 4

Write the equation which represents the enthalpy change of combustion of ethane.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>BEFORE YOU START>Q 4

Write the equation which represents the enthalpy change of neutralisation of sulphuric acid by sodium hydroxide.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>BEFORE YOU START>Q 5

Write the precise definitions of the enthalpy changes that are represented by the symbols $∆ {H_{r}}^{\circ}, ∆ {H_{f}}^{\circ}, ∆ {H_{neut}}^{\circ}$ and $∆ {H_{c}}^{\circ}$ .