Eduqas A-Level Chemistry A410QS
Formulae and Equations
Basic Ideas About Atoms
Chemical Calculations
Bonding
Solid Structures
The Periodic Table
Simple Equilibria and Acid-Base Reactions
Thermochemistry
Rates of Reaction
The Wider Impact of Chemistry
Organic Compounds
Hydrocarbons
Halogenoalkanes
Alcohols and Carboxylic Acids
Instrumental Analysis
Redox and Standard Electrode Potential
Redox Reactions
Chemistry of the P-Block
Chemistry of the D-Block Transition Metals
Chemical Kinetics
Enthalpy Changes for Solids and Solutions
Entropy and Feasibility of Reactions
Equilibrium Constants
Acid-Base Equilibria
Stereoisomerism
Aromaticity
Alcohols and Phenols
Aldehydes and Ketones
Carboxylic Acids and Their Derivatives
Amines
Amino Acids, Peptides and Proteins
Organic Synthesis and Analysis
Specified Practical Work
Practical Skills and Techniques
Mathematical Skills in Chemistry
Thermochemistry
Calculating enthalpy changes from experimental data
- 3 things to know
- Components 1 and 2
Overview
Recall questions on q = mcΔT and what each symbol means, which mass is used in a solution reaction, converting the heat change to a molar enthalpy change, the sign convention, and worked combustion, neutralisation and dissolving calculations checked in both directions.
What you need to know
Answer each one before you reveal it.
State the value of the specific heat capacity of water normally used in calorimetry calculations, with its units
Why can a temperature change be substituted in either degrees Celsius or kelvin?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Give the relationship used to calculate the heat energy transferred to a measured mass of water.
Model answer
The heat transferred is q = mcΔT, where m is the mass of water, c is its specific heat capacity and ΔT is the temperature change.
- 2
What is meant by the specific heat capacity of a substance?
Model answer
It is the energy needed to raise the temperature of one gram of the substance by one kelvin.
- 3
State the value of the specific heat capacity of water normally used in these calculations, with its units.
Model answer
The value used is 4.18 J g⁻¹ K⁻¹.
- 4
Why can a temperature change be substituted in either degrees Celsius or kelvin?
Model answer
The two scales have divisions of the same size, so a difference of one degree Celsius equals a difference of one kelvin.
- 5
How is an enthalpy change per mole obtained from a measured heat energy?
Model answer
The heat energy in kilojoules is divided by the number of moles of the substance that reacted, and a negative sign is added if the temperature rose.
- 6
Burning 0.92 g of ethanol raised the temperature of 100 g of water by 30.0 °C. Calculate the heat energy transferred to the water.
Model answer
q = 100 × 4.18 × 30.0 = 12540 J, which is 12.5 kJ.
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