Using dots (•) and cross (x) show the formation of Carbon (II) oxide gas (1mk)
Name two types of bonds present in the molecule in ‘a’ above (2mks)
(a) In Kenya, sodium carbonate is extracted from trona at Lake Magacli.
(i) Give the formula of trona.
(ii) Name the process of extracting sodium carbonate from trona.
(b) The flow chart in Figure 5 summarises the steps involved in the production of sodium carbonate.
Use it to answer the questions that follow.
(i) Name the process illustrated in Figure 5.
(ii) Identify the starting raw materials required in the production of sodium carbonate.
(iii) Write equations for the two reactions that occur in the carbonator.
(iv) Name two substances that are recycled.
(vi) Write an equation for the reaction that produces solution Z.
(vii) Apart from softening hard water, state two other uses of sodium carbonate.
Figure 2 is a section of the periodic table. Study it and answer the questions that follow. The letters do not represent the actual symbols of elements.
(a) (i) Select elements which belong to the same chemical family.
(ii) Write the formulae of ions for elements in the same period.
(b) The hrst ionisation energies of two elements K and M at random are 577 kJ/mol and 494 kJ/mol
(i) Write equations for the 1ˢᵗ ionisation energies for elements K and M and indicate their energies.
(iii) Write the formula of the compound formed when L and I react.
(iv) Give one use of elemcnt V.
(c) (i) State anothcr group that G can be placcd in Figure 1. Explain.
(ii) How do the reactivity of elements J and K compare? Explain.
(d) (i) Elements L and M form chlorides.
Complete the following table by writing the formulae of each chloride and state the nature of the solutions.
(ii) The chloride of element M vapourises easily while its oxide has a high melting point. Explain.
Explain why a solution of sodium chloride Conducts electricity while that of sugar does not.
Figure 5 represents a grid that is part of the periodic table. Study it and answer the questions that follow. The letters are not the actual symbols of the elements.
(a) Write the electron arrangement of element C.
(b) On the grid provided, show with a tick (✓) the position of element D whose atomic number is 18.
(c) Element E is more reactive than A. Explain.
(b) period 3, group 8
(c) E has a bigger atomic radius than A / the valence electrons of element E are further from the nucleus, hence loosely held by the positive nucleus and requires less energy to be removed during reaction.
A has a smaller atomic radius than E / the valence electrons of element
A are closer to the nucleus, hence strongly held by the positive nucleus and requires more energy to be removed during a reaction.
You are provided with solid potassium hydrogen carbonate. Describe how a solid sample of potassium nitrate can be prepared.
Measure a certain volume of dilute nitric(V) acid and place it in a beaker;
Add potassium hydrogen carbonate little by little as the mixture is stirred until effervescence stops;
Evaporate the solution to saturation and allow to cool for crystals to form;
Dry the crystals in between filter papers.
(a) Element U has atomic number 12 while element V has atomic number 16. How do the melting points of their oxides compare? Explain.
(a) Explain why it is not advisable to prepare a sample of carbon(IV) oxide using barium carbonate and dilute sulphuric(VI) acid.
(b) State a method that can be used to collect dry carbon(IV) oxide gas. Give a reason.
(a)The reaction starts but soon stops.
This is because the insoluble barium sulphate produced forms a coating on the surface of the barium carbonate preventing further reaction and evolution of carbon(IV) oxide gas.
(b) Downward delivery.
Carbon(TV) oxide is denser than air.
W is a colourless aqueous solution with the following properties:
(ii) Give the identity of W.
(iii) Name the colourless solution formed in (II) and (III).
(iv) Write an ionic equation for the reaction indicated in (V).
(b) Element V conducts electricity and melts at 933K. When chlorine gas is passed over heated V, it forms a vapour that solidifies on cooling. The solid chloride dissolves in water to form an acidic
solution. The chloride vapour has a relative molecular mass of 267 and contains 19.75% of V. At a higher temperature, it dissociates to a compound of relative molecular mass 133.5. When aqueous
sodium hydroxide is added to the aqueous solution of the chloride, a white precipitate is formed which dissolves in excess alkali. (V = 27.0 ; CI = 35.5)
(i) Determine the:
(iii) Write an equation for the reaction that form a white precipitate with sodium hydroxide.
In terms of structure and bonding, explain why graphite is used as a lubricant in machines.
Figure 6 shows part of the periodic table. The letters are not the actual symbols of the elements. Stud it and answer the questions that follow.
(a) Write an equation for the reaction between M and K.
(b) Select the element which can form an ion with a charge of +3.
(c) An element J has atomic number 15. Indicate with a tick (✓), on the part of the periodic table the position of J.
The atomic numbers of some elements P, Q, R and S are 6, 8, 12 and 17 respectively.
(a) Draw the dot (•) and cross (X) diagrams for the compounds formed when:
(i) R and Q react
(ii) P and S react.
(b) Explain why the melting point of the compound formed by P and S is lower than that formed by R and Q.
Starting with copper, describe how a pure sample of copper(II) carbonate can be prepared.
An oxide of element K has the formula K2O5.
(a) Determine the oxidation number of K.
(b) To which group of the periodic table does K belong?
Table 1 shows the atomic numbers and the first ionisation energies of three elements. The letters are not actual symbols of the elements. Use it to answer the questions that follow.
(a) Explain the trend in first ionisation energy from A to C.
(b) Write the electronic configuration for the ion of C.
(a) Ionisation energy decreases down the group 1 elements.
This is because atomic radii increases from A to C (down the group) /outermost electron is far from nucleus hence requires less energy to be lost during reaction.
(b)Electron configuration of ion of C- 2.8.8
Maurice Atika is a teacher and a netprenuer.