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The diagrams below show the electron arrangement in two compounds.
(a) In a water molecule, each hydrogen atom is bonded to the oxygen atom by sharing a pair of electrons. Why does an oxygen atom share two pairs of electrons rather than just one pair?
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(b) Describe how a potassium atom becomes a potassium ion.
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(c) Why is there a bond between the ions in potassium chloride?
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(d) Solid potassium chloride is a poor conductor of electricity. When dissolved in water it is a good conductor. Explain.
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Vanadium is a transition element.
(a) An atom of the most common isotope of vanadium can be represented as $^{51}_{23}V$.
Complete the following table to show the number of protons, electrons and neutrons in each particle.
[Table_1]
| particle | number of protons | number of electrons | number of neutrons |
|---|---|---|---|
| $^{51}_{23}V$ | |||
| $^{51}_{23}V^{3+}$ | |||
| $^{50}_{23}V$ |
(b) The major use of vanadium is to make vanadium steel alloys.
(i) Explain the phrase *steel alloys*.
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(ii) State the name and use of another steel alloy.
name .........................................................................................................................
use ...........................................................................................................................[2]
(c) Two of the oxidation states of vanadium are +3 and +4.
(i) Write the formula of vanadium(III) oxide and of vanadium(IV) oxide.
vanadium(III) oxide ..........................................................................................
vanadium(IV) oxide ..........................................................................................[2]
(ii) Vanadium(III) oxide is basic and vanadium(IV) oxide is amphoteric. Describe how you would obtain a sample of vanadium(III) oxide from a mixture of these two oxides.
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(a) To find the order of reactivity of the metals, cobalt, magnesium, silver and tin, the following experiments were carried out.
[Table_1]
(i) Give as far as possible the order of reactivity of these metals. Write the least reactive first.
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(ii) What additional experiment needs to be done to put all four metals in order of reactivity?
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(iii) Write an ionic equation for the reaction between tin atoms and silver(I) ions. Indicate on the equation the change which is oxidation.
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(b) Sodium is a more reactive metal than magnesium. Sodium compounds are more stable than magnesium compounds.
In an experiment, their hydroxides were heated. If the hydroxide did not decompose write 'no reaction' otherwise complete the equation.
NaOH $\rightarrow$ .............................................
Mg(OH)$_2$ $\rightarrow$ ............................................. [2]
(c) A cell consists of two different metal electrodes in an electrolyte. Three possible cells are shown below.
(i) Why is the more reactive metal the negative electrode?
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(ii) How can you deduce that zinc is more reactive than tin?
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(iii) How could you change the zinc/copper cell to have a voltage greater than 1.1 V?
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(iv) Complete the labelling of the zinc/tin cell.
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The electrolysis of concentrated aqueous sodium chloride, between inert electrodes, is used to make four important chemicals.
hydrogen
chlorine
sodium hydroxide
sodium chlorate(I)
(a) The ions present in the electrolyte are $\text{Na}^+$, $\text{H}^+$, $\text{Cl}^-$ and $\text{OH}^-$.
(i) Hydrogen ions are discharged at the negative electrode (cathode). Write an equation for this reaction. [2]
(ii) The hydrogen ions are from the water.
$\text{H}_2\text{O} \rightleftharpoons \text{H}^+ + \text{OH}^- $
Suggest an explanation why the concentration of hydroxide ions increases. [2]
(iii) When a dilute solution of sodium chloride is used, chlorine is not formed at the positive electrode (anode), a different gas is produced. Name this gas. [1]
(iv) State an example of an inert electrode. [1]
(b) (i) State a use of hydrogen. [1]
(ii) Why is chlorine used to treat the water supply? [1]
(c) Sodium chlorate(I) is made by the reaction between chlorine and sodium hydroxide. It is used as bleach but over time it decomposes.
$2\text{NaClO}(aq) \to 2\text{NaCl}(aq) + \text{O}_2(g)$
The rate of decomposition can be studied using the apparatus shown below.
(i) How could you measure the rate of decomposition of sodium chlorate(I)? [1]
(ii) Describe how you could show that the rate of decomposition of sodium chlorate(I) is a photochemical reaction. [2]
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(a) Ethanoic acid is a typical carboxylic acid. It forms ethanoates.
(i) Complete the following equations.
Mg + ...............CH$_3$COOH $\rightarrow$ ................................. + .................................
[2]
sodium + ethanoic $\rightarrow$ ................................ + ................................
hydroxide acid ................................
[1]
(ii) Ethanoic acid reacts with ethanol to form an ester. Give the name of the ester and draw its structural formula. Show all of the bonds.
name ................................................................................................................
structural formula ...........................................................................................
[2]
(b) Maleic acid is an unsaturated acid. 5.8 g of this acid contained 2.4 g of carbon, 0.2 g of hydrogen and 3.2 g of oxygen.
(i) How do you know that the acid contained only carbon, hydrogen and oxygen?
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[1]
(ii) Calculate the empirical formula of maleic acid.
Number of moles of carbon atoms = .................................
Number of moles of hydrogen atoms = .................................
Number of moles of oxygen atoms = .................................
The empirical formula is ....................................................................................
[3]
(iii) The mass of one mole of maleic acid is 116 g. What is its molecular formula?
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[2]
(iv) Maleic acid is dibasic. One mole of acid produces two moles of H$^+$. Deduce its structural formula.
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[2]
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The Kinetic Theory explains the properties of matter in terms of the arrangement and movement of particles.
(a) Nitrogen is a gas at room temperature. Nitrogen molecules, $\text{N}_2$, which are spread far apart move in a random manner at high speed.
(i) Draw a diagram showing the arrangement of the valency electrons in a nitrogen molecule.
Use × to represent an electron from a nitrogen atom. [2]
(ii) How does the movement and arrangement of the molecules in a crystal of nitrogen differ from those in gaseous nitrogen? [3]
(b) Use the ideas of the Kinetic Theory to explain the following.
(i) A sealed container contains nitrogen gas. The pressure of a gas is due to the molecules of the gas hitting the walls of the container.
Explain why the pressure inside the container increases when the temperature is increased. [2]
(ii) The following apparatus can be used to measure the rate of diffusion of a gas.
The following results were obtained. [Table_1]
Explain why nitrogen diffuses faster than chlorine. [2]
Explain why the nitrogen diffuses faster at the higher temperature. [1]
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Synthetic polymers are widely used in the modern world.
(a) Their use has brought considerable advantages to modern life as well as some disadvantages.
(i) Suggest two advantages of a plastic bucket compared to a steel bucket.
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(ii) Name two uses of man-made fibres, such as nylon and Terylene.
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(iii) Describe the pollution caused by synthetic polymers.
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(b) One type of polymer is formed by addition polymerisation.
(i) The structural formula of an addition polymer is given below.
Give the name and structural formula of the monomer.
name of monomer .......................................................... [1]
structural formula of monomer
(ii) Draw the structural formula of the addition polymer formed by the polymerisation of phenylethene. The structural formula of phenylethene is given below.
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(c) Nylon is made by condensation polymerisation. It has the structural formula shown below.
(i) Name the linkage in this polymer.
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(ii) Name the natural macromolecules which have the same linkage.
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(iii) Deduce the formulae of the two monomers which reacted to form the nylon and water.
monomer .......................................................... [2]
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