KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
What type of bond is formed when lithium and Fluorine react? Explain
(Atomic numbers: Li = 3 and F = 9)
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a) the schematic diagram shows part of the Solvay process used for the manufacture of sodium carbonate.
i) Explain how the sodium chloride required for this process is obtained from sea water.
ii) Two main reactions take place in UNIT I . The first one is the formation of ammonium hydrogen carbonate. I. Write an equation for this reaction II. Write an equation for the second reaction iii) State how the following are carried out: I Process I II) Process II iv)In an experiment to determine the percentage purity of the sample of sodium carbonate produced in the Solvay process, 2.15 g of the sample reacted completely with 40.0cm3 of 0.5 M sulphuric acid. I calculate the number of moles of sodium carbonate that reacted. II Determine the percentage of sodium carbonate in the sample. (Na= 23.0, C= 12.0, O = 16.0) b) Name two industrial uses of sodium carbonate
Study the information given in the table below and answer the questions that follow. The letters do not represents the actual symbols of the elements
(a) Select the elements which belong to the same
(e) The aqueous sulphate of element W was electrolyzed using inert electrodes Name the products formed at the:
The set – up below was used to prepare anhydrous chlorides of a number of elements in a laboratory where no fine cupboard was available. The chlorides were to be collected in flask
The following table shows the melting and boiling points of the chlorides that were prepared.
More Quiz
(a) The table below gives the solubilities of hydrated copper (II) sulphate in mol dm3 at different temperatures (i) On the grid provided, plot a graph of solubility of copper (II) sulphate (vertical axis) against temperature. (ii) From the graph, determine the mass of copper (II) sulphate deposited when solution is cooled from 700C to 400C. (Molar mass of hydrated copper (II) sulphate = 250g) (b) In an experiment to determine the solubility of sodium chloride, 5.0cm3 of a saturate solution of sodium chloride weighing 5.35g were placed volumetric and diluted to a total volume of 250cm3. 25.0cm3 of the dilute solution chloride completely reacted with 24cm3 of 0.1M silver nitrate solution. AgNO3(aq) + NaCI(aq) → AgCl(s) + NaNO3(aq) Calculate: (i) Moles of silver nitrate in 24cm3 of solution (ii) Moles of sodium chloride in 25.0cm3 of sodium (iii) Moles of sodium chloride in 250cm3 of solution (iv) Mass of sodium chloride in 5.0cm3 of saturated sodium chloride Solution (Na = 23.0, CI = 35.5) (v) Mass of water in 5.0cm3 of saturated solution of sodium chloride (vi) The solubility of sodium chloride in g/100 water
ANSWERS
(a) SiH4 it has a higher boiling point
(b) No hydrogen bonding in CH4 and SiH4 while the hydrogen bond in H2O is stronger than that in H2S
Give the name of the product formed when magnesium reacts with phosphorus.
ANSWERS
ANSWERS
The table below gives the energy required to remove the outermost electron for some group I elements
Arrange the elements in order of their reactivity starting with the most reactive
Expected Response
Starting with 50 cm3 of 2.8M sodium hydroxide, describe how a sample of pure sodium sulphate crystals can be prepared.
Using dots (.) and crosses (x) , show bonding in:
a) The compound formed when nitrogen reacts with fluorine (Atomic numbers F=9, N=7); b) Sodium oxide.(Atomic numbers Na= 11, 0 = 8)
An isotope of element E has 34 neutrons and its mass number is 64. E forms a cation with 28 electrons. Write the formula of the cation with 28 electrons. Write the formula of the cation indicating the mass and atomic numbers.
In terms of structure and bonding, explain why the melting point of oxygen is much lower than that of sodium.
ANSWER
ANSWERS
(i) 2.8.8 (ii) 2.8.2
Describe how a solid sample of lead (II) Chloride can be prepared using the following reagents, dilute nitric acid, dilute hydrochloric acid and lead carbonate.
Expected Response
ANSWERS
(a) Energy required to remove 1 mole of electrons from 1 mole of gaseous atoms
(b) B 418??? It loses electrons most readily Reject lowest i.e. Mg (HCO3) 2 aq →MgCS O3 + H2O + CO2 (g)
a) Write an equation to show the effect of heat on the nitrate of:
(i) Potassium b) The table below gives information about elements A1,A2,A3, and A4
(i) In which period of the periodic table is element A2? Give a reason
(ii) Explain why the atomic radius of: I A1 is greater than that of A2; II A4 is smaller than its ionic radius (iii) Select the element which s in the same group as A3 (iv) Using dots (.) and crosses(x) to represent outermost electrons. Draw a diagram to show the bonding in the compound formed when A1 reacts with A4
ANSWERS
(a) Neutralization
(b)(i)Calcium hydrogen carbonate (ii)Drying agent Extraction of sodium metal
When solid B1 was heated, a gas which formed a white precipitate when passed through lime water was produced. The residue was dissolved in dilute nitric (V) acid to form a colourless solution B2. when dilute hydrochloric acid was added to solution B2 a white precipitate which dissolved on warning was formed.
a) Write the formula of the; I Cation in solid B1 II anion in solid B1 b) Write an ionic equation for the reaction between the resdue and dilute nitric (V) acid.
Diamond and graphite are allotropes of carbon. In terms of structure and bonding explain the following.
The grid below is part of the periodic table. Use it to answer the questions that follow, (the letters are not the actual symbols of the elements).
a) Indicate on the grid the position of an element represented by letter V whose atomic number is 14.
b) Select a letter which reaction between Q and T.
Starting with copper metal, describe how a sample of crystals of copper (II) chloride may be prepared in the laboratory.
The table below gives atomic numbers of elements represented b the letters A, B, C and D.
Use the information to answer the questions that follow.
a) Name the type of bonding that exists in the compound formed when A and D react b) Select the letter which represents the best oxidizing agent. Give a reason for your answer.
ANSWERS
(a)Ionic/ electrovalent
(b)Has 7 electrons in its outermost energy level and hence easily gains an electron to complete the octet or it is most electronegative.
ANSWERS
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