IGCSE Chemistry 0620 Paper 41, Oct/Nov 2024

happens when an acid reacts with an alkali

reaches a position of equilibrium

involves particles changing from fixed positions to being mobile, but still touching

are physical changes ................................................................... and ...................................................................

is caused by gas particles colliding with each other.

Define the term nucleon number.

State the connection between the number of occupied electron shells in an atom and the period number of that element.

Write the electronic configuration of the following atom and ion. ${}_{14}^{28}\mathrm{S}\mathrm{i}$ ............................................... ${}_{17}^{37}{\mathrm{C}\mathrm{l}}^{-}$ .............................................

Complete Table 2.1. Table 2.1

A sample of thallium, $\mathrm{T}\mathrm{l}$, contains two isotopes, ${}^{203}\mathrm{T}\mathrm{l}$ and ${}^{205}\mathrm{T}\mathrm{l}$. Define the term isotopes.

The relative abundance of ${}^{203}\mathrm{T}\mathrm{l}{:}^{205}\mathrm{T}\mathrm{l}$ is in the ratio $3:7$. Calculate the relative atomic mass of thallium in the sample to one decimal place. relative atomic mass = ..............................

Suggest why these two isotopes have identical chemical properties.

Complete the symbol equation for this reaction. Include state symbols. $\mathrm{C}\mathrm{u}\mathrm{O}(\text{..........})+{\mathrm{H}}_2{\mathrm{S}\mathrm{O}}_4(\text{..........})\to {\mathrm{C}\mathrm{u}\mathrm{S}\mathrm{O}}_4(\text{..........})+\text{...........................}(\mathrm{l})$

State one observation which shows that copper(II) oxide is added in excess.

Describe how aqueous copper(II) sulfate can be separated from the reaction mixture.

Crystals of hydrated copper(II) sulfate can be obtained from aqueous copper(II) sulfate by crystallisation. State what is meant by the term hydrated.

Write the formula of hydrated copper(II) sulfate.

Describe how this crystallisation is done.

Aqueous copper(II) sulfate undergoes electrolysis using graphite electrodes. State why aqueous copper(II) sulfate conducts electricity.

Give two reasons why the electrodes are made of graphite. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Describe how the appearance of the electrolyte changes during the electrolysis of aqueous copper(II) sulfate.

Describe what is seen at the cathode during the electrolysis of aqueous copper(II) sulfate.

Write the ionic half-equation for the reaction at the anode.

State two differences seen if the electrolysis is repeated using copper electrodes instead of graphite electrodes. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

The equation for this reaction is shown. $$2{\mathrm{M}\mathrm{g}(\mathrm{N}\mathrm{O}}_3{)}_2\to 2\mathrm{M}\mathrm{g}\mathrm{O}+4{\mathrm{N}\mathrm{O}}_2+{\mathrm{O}}_2$$ State the change in oxidation number of nitrogen, $\mathrm{N}$, in this reaction. from ............................ to ............................

Identify the element which is oxidised in this reaction.

Calculate the volume of ${\mathrm{N}\mathrm{O}}_2$ gas, at r.t.p., formed when $7.40\mathrm{g}$ of ${\mathrm{M}\mathrm{g}(\mathrm{N}\mathrm{O}}_3{)}_2$ is heated. Use the following steps. ● Calculate the $M_r$ of ${\mathrm{M}\mathrm{g}(\mathrm{N}\mathrm{O}}_3{)}_2$. .............................. ● Calculate the number of moles of ${\mathrm{M}\mathrm{g}(\mathrm{N}\mathrm{O}}_3{)}_2$ used. .............................. mol ● Determine the number of moles of ${\mathrm{N}\mathrm{O}}_2$ formed. .............................. mol ● Calculate the volume of ${\mathrm{N}\mathrm{O}}_2$ gas, in ${\mathrm{c}\mathrm{m}}^3$, at r.t.p. .............................. ${\mathrm{c}\mathrm{m}}^3$

Magnesium oxide, $\mathrm{M}\mathrm{g}\mathrm{O}$, is an ionic compound. Complete the dot-and-cross diagram in Fig. 4.1 of the ions in magnesium oxide. Give the charges on each of the ions.

Oxygen is a covalent molecule. Complete the dot-and-cross diagram in Fig. 4.2 of a molecule of oxygen. The inner shells have been drawn.

Hydrogen is used in fuel cells to produce electricity in vehicles. Name the substance which combines with hydrogen in a fuel cell.

Give one advantage and one disadvantage of using fuel cells instead of gasoline in vehicle engines. advantage ........................................................................................................................... disadvantage ......................................................................................................................

Hydrogen gas can be made from petroleum by a two-step procedure. step 1 Petroleum is separated into different components. step 2 Large molecules obtained in step 1 are converted into smaller molecules including hydrogen gas. Name the process used in step 1.

Name the process used in step 2.

Organic compounds contain hydrogen atoms. Calculate the number of hydrogen atoms in $44.0\mathrm{g}$ of the ester methyl propanoate, ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{C}\mathrm{H}}_3$. One mole of ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{C}\mathrm{H}}_3$ contains $6.02\times {10}^{23}$ molecules. Give your answer in standard form. number of hydrogen atoms = ..................................................

For each of the homologous series shown, name a member that contains six hydrogen atoms. ● alkanes ............................................................ ● alkenes ............................................................ ● alcohols ........................................................... ● carboxylic acids ...............................................

Unsaturated alkenes are converted into saturated alkanes by reaction with hydrogen gas. State why alkenes and alkanes are hydrocarbons.

State why alkenes are unsaturated.

Name the catalyst needed to convert alkenes into alkanes.

Explain why the conversion of alkenes into alkanes is an addition reaction.

State the type of polymerisation reaction that occurs when natural polyamides form.

State the term given to natural polyamides.

An amino acid is represented as shown in Fig. 6.1. Complete Fig. 6.2 to show the general structure of an amino acid. Show all of the atoms and all of the bonds in the functional groups.

Three different amino acids are represented as shown in Fig. 6.3. Complete the diagram in Fig. 6.4 to show the part of the structure of the natural polyamide that forms when the three amino acids, A, B and C, combine. Show all of the atoms and all of the bonds in the linkages.

A mixture of the three amino acids, A, B and C, can be separated and the amino acids identified using paper chromatography. Complete the equation for $R_{\mathrm{f}}$. $R_{\mathrm{f}}=$

A sample of the mixture of the three amino acids, A, B and C, is placed onto the baseline and a chromatogram is allowed to develop as shown in Fig. 6.5. The finished chromatogram is shown in Fig. 6.6. The amino acids, A, B and C, are colourless. Water is used as the solvent. Explain why the baseline is drawn in pencil.

State the type of substance used to make the colourless amino acids visible on the chromatogram in Fig. 6.6.

Explain why in Fig. 6.6 only two spots are seen from the mixture of three amino acids.

Suggest how the experiment can be changed to separate all three amino acids.