Why must an air bubble be removed from the burette tip before the titration begins?

If the bubble escapes during the titration, the volume recorded is larger than the volume actually delivered.

Explain why the conical flask is rinsed with distilled water rather than with the alkali.

Rinsing with alkali would add extra moles of alkali and make the titre too large, while water does not change the amount present.

Name a suitable indicator for an acid-alkali titration and give its colour change as acid is added.

Phenolphthalein changes from pink to colourless.

Edexcel GCSE Chemistry 1CH0

Key Concepts in Chemistry

Topic overview Formulae, word equations and balanced equations Hazard symbols and assessing risk The changing model of the atom Protons, neutrons and electrons The nucleus, mass number and atomic mass Elements and isotopes Calculating particle numbers and relative atomic mass Mendeleev's periodic table How the modern periodic table is arranged Electronic configuration and the periodic table How ionic bonds form Ions in ionic compounds Formulae of ionic compounds and ionic equations Naming compounds and the ionic lattice Covalent bonds and molecules Dot and cross diagrams for simple molecules Classifying substances and the properties of ionic compounds Properties of simple molecular substances, and forms of carbon Graphite and diamond Fullerenes and graphene Polymers and models of bonding The properties of metals Relative formula mass and percentage composition Empirical and molecular formulae Conservation of mass in closed and open systems Reacting masses from balanced equations Concentration in grams per cubic decimetre Moles and the Avogadro constant Limiting reactants and stoichiometry

States of Matter and Mixtures

Topic overview The three states of matter and changes of state Energy changes during changes of state, and predicting state Pure substances and melting point data Choosing a separation technique Separating a mixture in practice Paper chromatography and interpreting a chromatogram Investigating inks by distillation and chromatography Making water potable

Chemical Changes

Topic overview Acids, alkalis and the pH scale Indicators: litmus, methyl orange and phenolphthalein Hydrogen ion concentration and the pH scale Investigating pH change when neutralising an acid Dilute and concentrated, weak and strong acids Bases and alkalis Reactions of acids, and testing for hydrogen and carbon dioxide Neutralisation and its ionic equation Preparing soluble salts from insoluble and soluble reactants Preparing pure, dry copper sulfate crystals Carrying out an acid-alkali titration Solubility rules Predicting precipitates and preparing an insoluble salt Electrolytes and what electrolysis is Movement of ions and predicting the products of molten electrolysis Electrolysis with inert electrodes Writing half equations Oxidation and reduction at the electrodes Electrolysis of copper sulfate solution Investigating the electrolysis of copper sulfate

Extracting Metals and Equilibria

Topic overview Investigating the reactivity of metals Displacement reactions as redox reactions The reactivity series Ores, oxidation and reduction Choosing a method to extract a metal Biological methods of metal extraction Corrosion resistance and recycling metals Life cycle assessment Reversible reactions and dynamic equilibrium The Haber process and its conditions Changing the position of an equilibrium

Transition Metals, Quantitative Chemistry and Industrial Processes

Topic overview Transition metals and their properties Corrosion and electroplating Preventing rusting Alloys and alloy steels How the uses of metals relate to their properties Concentration in mol dm-3 and titration calculations Carrying out an accurate titration Percentage yield Atom economy and choosing a reaction pathway Molar volume of a gas Avogadro's law and gas volumes The Haber process Conditions used in industrial reactions Fertilisers and ammonium salts Preparing ammonium sulfate in the lab and in industry Chemical cells and fuel cells Evaluating fuel cells

Groups in the Periodic Table

Topic overview The groups of the periodic table, and the alkali metals Reactions of the alkali metals with water The pattern in alkali metal reactivity and why it happens Physical properties of the halogens The test for chlorine, and halogens reacting with metals Hydrogen halides, and explaining halogen reactivity Displacement reactions of the halogens Group 0: the noble gases

Rates of Reaction and Energy Changes

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Fuels and Earth Science

Topic overview Hydrocarbons and crude oil Fractional distillation and the fractions Properties of the fractions and homologous series Complete and incomplete combustion Carbon monoxide and soot Pollutants and acid rain Hydrogen and fossil fuels compared Cracking and why it is necessary The Earth's early atmosphere How the oceans formed and how oxygen appeared The test for oxygen and the greenhouse gases Today's atmosphere and evidence for climate change

Chemical Analysis, Organic Chemistry and Materials

Topic overview Why an ion test must be unique, and flame tests Tests for metal ions and for ammonia Tests for carbonate, sulfate and halide ions Identifying the ions in an unknown salt Instrumental methods and flame photometry Alkanes and why they are saturated Alkenes and why they are unsaturated Reactions of alkenes, and combustion What a polymer is, and how poly(ethene) forms Other addition polymers, and monomers from polymers Uses of polymers, and natural polymers including DNA Polyesters and condensation polymerisation Problems with polymers and recycling Alcohols and the -OH functional group Comparing the energy released by alcohol fuels Making ethanol by fermentation and distillation Carboxylic acids and the -COOH functional group Oxidising alcohols to carboxylic acids, and homologous series The size of nanoparticles Uses and risks of nanoparticles Choosing a material for a use

Transition Metals, Quantitative Chemistry and Industrial Processes

Carrying out an accurate titration

3 things to know
Paper 1

Overview

The pipette, burette and conical flask and how each is rinsed, removing air bubbles, suitable indicators and their colour changes, reaching the end point accurately, reading the burette, and concordant titres and the mean titre.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Which piece of apparatus is used to transfer an accurate fixed volume of alkali into the conical flask?

Key term

Which piece of apparatus holds the acid so that the exact volume added can be measured?

Key term

Why is the burette rinsed with the acid before it is filled?

Questions from this subtopic

Each one with the model answer underneath.

1
Which piece of apparatus is used to transfer an accurate fixed volume of alkali into the conical flask?
Model answer
A pipette, used with a pipette filler.
2
Which piece of apparatus holds the acid so that the exact volume added can be measured?
Model answer
A burette holds the acid.
3
Why is the burette rinsed with the acid before it is filled?
Model answer
Rinsing removes water that would otherwise dilute the acid and make the titre too large.
4
Why must an air bubble be removed from the burette tip before the titration begins?
Model answer
If the bubble escapes during the titration, the volume recorded is larger than the volume actually delivered.
5
Explain why the conical flask is rinsed with distilled water rather than with the alkali.
Model answer
Rinsing with alkali would add extra moles of alkali and make the titre too large, while water does not change the amount present.
6
Name a suitable indicator for an acid-alkali titration and give its colour change as acid is added.
Model answer
Phenolphthalein changes from pink to colourless.

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Key Concepts in Chemistry

States of Matter and Mixtures

Chemical Changes

Extracting Metals and Equilibria

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