-
- Define the term isotopes [1mk]
- The table below shows the isotopic composition of element Q
Isotope
relative
90.92
X
0.26
- In , what does 21 represent? [1mk]
- Determine value of X [1mk]
- Hence calculate R.A.M of Q [2mks]
-
- State Grahams law of diffusion [1mks]
- 400cm3 of nitrogen gas diffuse through a porous plug in 120 seconds. How long would it take 360cm3of oxygen gas to diffuse under the same conditions?
{N=14, O=16} [3mks]
- Acid rain is formed when rain falls through air polluted with carbon (IV) oxide and Sulphur(IV)oxide. Identify two acids possibly present in such an acid rain [2mks]
- Ca2+ is one of the cations present in hard water that makes water to be hard
- Identify another cation responsible for water hardness [1mk]
- One method of removing permanent hardness in water is by use of ion exchanger
- State two other methods that can be used [2mks]
- After continuous use the ion exchanger column gradually looses the water hardness. How can its ability be recovered? [1mk]
- State one disadvantage of water hardness [1mk]
- The empirical formulae of a compound is given as C2H4O. Given that its R.M.M is 88, find its molecular formulae {C=12, H=1, O=16} [2mks]
- 29 grams of a saturated solution of salt M at 350C yield 8.5 grams of solid when evaporated to dryness. Determine the solubility of the salt at 350C [2mks]
- In an experiment, copper metal was heated in the air to form a black solid T. dilute Sulphuric {VI} acid was then added to solid T resulting to formation of solution W, after which Ammonia was then added to solution W drop wise till excess
- Identify solid T [1mk]
- Write a chemical equation for the reaction leading to formation of solution W [1mk]
- State the observations made when the am monia solution was added to solution W drop wise till excess [2mks]
- What name is given to each of the following?
- Ability of a metal to be beaten/ hammered to a sheet [1mk]
- Force of attraction that holds two molecules together [1mk]
- Draw the structures and name two hydrocarbons with molecular formulae C4H10 [4mks]
- 800cm3 of a gas exert a pressure of 520mmHg at 750C .What pressure would 700cm3 of the same gas exert at 1000C? [2mks]
- Aluminium is one of the metals that is commonly used in making cooking utensils. State two properties of aluminium that makes it suitable for this use [2mks]
- Given the following bond energies in KJmole-1
Bond Energy [KJmole-1]
C –C 348
C – H 414
Cl -Cl 243
C -Cl 432
H – Cl 340- Determine the enthalpy charge in the following reaction
C2H6 [g] + Cl2[g] → CH3CH2Cl[g] + HCl[g] [3mks] - state whether the reaction was exothermic or endothermic [1mk]
- Determine the enthalpy charge in the following reaction
- The grid below shows a section of the periodic table
- Which letter represents the least reactive element? Explain your answer [2mks]
- Which letter represents the most electropositive element? [1mk]
- What name is given to the family into which element X belongs to? [1mk]
- How does the electrical conductivity of element Y and Z compare? Explain [2mks]
- Describe how you can prepare a dry sample of lead (II) carbonate starting with lead (II) nitrate crystals [3mks]
- Explain why the relative molecular mass of NO2 is sometimes 92 instead of 46 [2mks]
- Using dots and crosses, show bonding in the following [3mks]
- H2O
- H2O+
- The diagram below shows part of a set-up used to prepare a solution of hydrogen chloride gas in water
- What property of hydrogen chloride gas makes it necessary to prepare its solution in water as shown on the diagram [1mk]
- Give two reagents that can be used to prepare hydrogen chloride [2mks
- State and explain the effect on red litmus paper when dropped in the resulting solution [2mks]
- When 3.1g of Copper {II} Carbonate were heated in a crucible until no further change in mass, solid L and gas M were formed
- Identify solid L and gas M [2mks]
- Write a chemical equation for the reaction that occurred [1mk]
- Given Cu=64, C=12,O=16, calculate the mass of the solid L that was formed [2mks]
- In terms of structure and bonding explain why silicon (IV) oxide has a higher melting point than phosphorous (IV) oxide [2mks]
- Briefly describe two experiments that can be used to distinguish nitrogen (I) oxide and Nitrogen (II) oxide [4mks]
- Manganese (IV) oxide is a common reagent used in the preparation of chloride gas using concentrated hydrochloric acid and preparation of oxygen gas using hydrogen peroxide
- State the role of manganese(IV) oxide in the preparation of;
- Chlorine gas [1mk]
- Oxygen gas [1mk]
- State two physical properties of chlorine gas [2mks]
- State the role of manganese(IV) oxide in the preparation of;
- Give two reasons why air is considered a mixture and not a compound [2mks]
- Sulphur has two allotropic forms
- Identify the two allotropic forms [2mks]
- Which of the allotropes is most stable at temperatures below 960C [1mk]
- Rusting is a common chemical process that occurs on the surface of materials made of iron
- What is the chemical name of rust [1mk]
- Identify two conditions that accelerate the rusting process [2mks]
MARKING SCHEME
-
- Isotopes are atoms of the same element with same atomic number but different mass number. √1
-
- Mass number √1
-
-
- Grahams law states that under the same conditions of temperature and pressure, the rate of diffusionof a gas is inversely proportional to the squireroot of its density. √1
-
- Carbonic acid √1
Sulphuric (IV) acid √1
-
- Mg2+ √1
-
- distillation√1
Precipitation by sodium carbonate √1 - by flashing it with brine/ concentrated sodium chloride√1
- distillation√1
- waste soap √1
Stains white clothes.
(Any one correct)
- Molecular mass=( E.F)n
- Mass of the solvent. 29.0- 8.5= 20.5
-
- copper (ii) oxide/ CuO√1
- CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l) √1
- pale blue ppt formed, which dissolves√ in excess ammonia solution to form deep blue solution.√
-
- malleable √1
- vandarwaals forces √1
- Alluminium is a good conductor of electricity √1
It is not easlycorroded √1
-
-
- Exothermic √1
-
-
- X, √1 has maximum number of electrons√1 in the outer most energy level hence has least tendency to loose or gain electrons.
- B √1
- Noble gases√1
- Z has more electrical conductivity because it has more delocalized electrons. √1
- Add lead (ii) nitrate to a beaker with distilled water and stir. √
filter√ to obtain a solution of lead (II) nitrate.
Add a solution of sodium carbonate √ (any soluble carbonate) to lead (ii) nitrate solution.
Filter √the mixture to obtain the insoluble lead (ii) carbonate as the residue
Rinse the residue with distilled water √
Dry it between filter papers√
- NO2 forms a dimer which is N2O4√1 hence the mass number doubles √1
-
- its highly soluble in water √1
- concentratedsulphuric(vi) acid and rock salt/ sodium chloride
- it remains red because the solution is acidic.
-
- Solid L- nCopper (ii) oxide √1
Gas M- carbon (iv) oxide√1 - CuCO3(s) → CuO +CO2(g)
- CuCO3(s) →CuO +CO2(g)
mm-124 82 44
given mass 3.1
- Solid L- nCopper (ii) oxide √1
- Silicon (iv) oxide√has a giant atomic√ structure with strong covalent bond while phosphorous (v) oxide has molecular √structure with weak van der waals forces of attraction. √
- Lower a glowing splint into a sample of each in gas jar. √1 nitrogen (i) oxide relights the glowing splint while nitrogen (ii) oxides does not. √1
Pass air through a sample of each in the gas jar nitrogen (ii) oxide is oxidized to brown nitrogen (iv) oxide while nitrogen (i) oxide does not react with air.
-
-
- acts as an oxidizing agent √1
- acts as a catalyst √1
- soluble in water √1
Green yellow gas √1
Its denser than air √1 - Any two correct
-
- Components of air are not chemically combined√1
Components of air can be separated by physical means√1
Each of the components of air retains its physical and chemical properties√1
Any two correct
-
- Rhombic sulphur√1
Monoclinic sulphur√1 - Rhombic sulphur√1
- Rhombic sulphur√1
-
- hydrated iron (iii) oxide √1
- salty condition √1
Acidic condition √1
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