MUSINGU HIGH SCHOOL

2017 AUGUST HOLIDAY ASSIGNMENT

CHEMISTRY FORM III

Attempt all questions in this paper

  1. A compound has empirical formula C3H6O and has a relative molecular mass of 116

a) Determine its molecular formula(3mks)

(H =1.0, C =12.0, O =16.0)

b) Calculate the percentage composition of carbon by mass in the molecular compound(3mks)

  1. 4.6g of a compound made up of carbon, Hydrogen and oxygen was completely burnt in oxygen 8.8g of carbon (IV) oxide and 5.4g of water were formed at e end of the experiment. Determine the simplest formula of the compound (C =12 H = 1 O =16 (4mks)
  1. When 1.44g of element X was heated in excess air, 2.08g of the oxide was formed. Determine the molecular formula if its molecular mass is 208 (R.A.M X=72, O =16 ) (3mks)
  1. a) State Graham’s law of diffusion(1mk)

b) Under similar conditions 100cm3 of oxygen diffused in 20 seconds, while 100cm3 of gas X diffused in 5 sec. Calculate the molar mass of gas (X =16.0) (3mks)

  1. 6.5g of calcium carbonate was heated strongly until there was no further change in mass. Calculate the mass of he residue. (Ca = 40, C = 12, O = 16)
  1. Calculate the number of chloride ions present in 25cm3 of chloride ions present in 25cm3 of 0.5M iron (III) chloride. (avogadro’s number 6 x 1023)
  1. 15cm3 of a solution containing 2.88g/dm3 of an alkali XOH completely reacts with 2cm3 of 0.45M Suphuric acid. Calculate the morality and relative atomic mass of X present in the alkali (4mks)
  1. 8g of sodium hydroxide were dissolved in 250cm3 of distilled water. Calculate the concentration of sodium hydroxide solution in moles per litre 923.0, O = 16.0) H = 1.0)

(3mks)

  1. 100cm3 of a mixture of ethane and excess of oxygen were ignited. When the final volume was cooled and bubbled through aqueous sodium hydroxide, it was reduced by 32cm3. calculate the composition of the original mixture and the volume of the residue oxygen at the same temperature and pressure (4mks)

i)Write ionic equations of the following

a) Zn(s) + CuSO4 Cu(s) + ZnSO4(aq)(2mks)

b) 2FeCl2(aq) + Cl2(g) 2FeCl3(aq)(2mks)

c) ZnCo3(s) + 2HCl ZnCl2(aq) + Co2 (g)+ H2O(l)

  1. The empirical formula of a compound is C2H5. When 11.6g of it was allowed to evaporate, if occupied 4.8dm3 at room temperature and pressure. What is its molecular formula (3mks)
  1. Study the table below. The letters do not represent the actual symbols of the element

Element / Atomic Number / Boiling Point
A
B
C
D
E / 3
13
16
18
19 / 1603
2743
718
87
1047

(a)Select the elements which belong to the same

i) Group(1mk)

ii) Period(1mk)

(b) i)Is gaseous state at room temperature. Explain (R tem is 250C)(2mk)

ii) Does not form an oxide(1mk)

c)The formula of the nitrate of element A

i) Equation for the reaction between element B and oxygen gas(2mks)

d) What type pf bond exists in the compound when elements and C react?(1mk)

Give a reason(1mk)

e) Explain why the boiling point of B is greater than that of element E(2mks)

  1. Use dot (.) and cross (x) diagram to show the structure of

a) Ammonia (NH3)(2mks)

b) Ammonium ion(NH4+)(2mks)

  1. When 27.8g of hydrated aluminum oxide (Al2O3.2H2O) was heated to a constant mass, 20.6g of aluminum oxide was obtained. Determine the value of X (H =1 O =16 Al = 27) (4mks)
  1. A compound contains 59% element X and 49% oxygen. Given that the relative formula mass of the compound is 78, determine its molecular formula (X = 23, O =16) (4mks)
  1. 25cm3 of a solution of 0.05m Suphuric acid require 35cm3 of a solution of potassium hydroxide. Determine the

a) concentration of the alkali in g/l.(3mks)

b) morality of the alkali in mol/dm3(1mk)

(K39, O =16, H =1)

  1. Determine the volume of carbon (IV) oxide formed when 6.25g of zinc carbonate is strongly heated to constant mass at room temperature and pressure. (Zn 65, C =12, O = 16 , molar gas volume at r.t.p = 24dm3.) (3mks)
  1. 0.2 moles of a metallic salt X2CO3 combined with 36g of water to form a hydrated salt X2CO.Hn2O. Determine the value of n in the above formula. (2mks)
  1. A piece of potassium metal was placed in a large beaker containing distilled water. The potassium reacted violently and finally disappeared, forming hydrogen gas and potassium hydroxide solution. This solution was diluted to one litre. On titration, 25.0cm3 of the resulting solution required 25.0cm3 0.01M Suphuric acid for complete neutralization. (K =39, O =16,H =H1.)

i) Write a balanced chemical equation for the reaction of potassium with water.(1mk)

ii) What is the concentration in moles per litre of the potassium hydroxide used in the titration? (2mks)

iii) Determine the mass of potassium placed in the beaker?(1mk)

  1. Calculate the volume of 0.1M sodium carbonate solution required to neutralize 25cm3 of 0.2M Suphuric acid. (2mks)
  1. 22.5cm3 of a solution of hydrochloric acid reacted with 25.0cm3 of 0.9M sodium hydroxide solution. Calculate the concentration of the acid in mol-1 and g-1 (H =1, Cl = 35.3) (4mks)
  1. a) Crystalline barium chloride,BaCl2.xH2O decomposes when heated according to the following equation:

Bacl2.xH2O Bacl2 + xH2O

If the percentage of water of crystallization was found to be 14.75%, calculate the value of x in the compound. (2mks)

(Ba =137, Cl =35.5 O =16.0,H = 1.0)

b)From the equation, C(s) + 2H2So4(l) Co2(g) + 2H2O(l) 2SO2(s)

calculate:

i) the mass of carbon oxidized by the action of 19.6g of Suphuric acid.(2mks)

ii)The volume of sulphur (IV) oxide measured at s.t.p, liberated in 100ml of hydrochloric acid. When there was no more reaction taking place, the crystals were washed and dried and found to weigh 1.87g.

calculate:

a) the morality of the acid(2mks)

b)the volume at s.t.p of carbon (IV) oxide liberated

(H = 1, C =12, O =16, Cl = 35.5, Ca = 40, molar gas volume = 22.4dm3)(2mks)

  1. A sample of hydrogen chloride gas was dissolved in water to make 25cm3 of the solution required 46cm3 of 11.0M sodium hydroxide

a) Calculate the number of moles of hydrochloric acid in 25cm3 of solution.(2mks)

b) Determine the mass of hydrogen chloride that was dissolved to make 250cm3 of solution.(Cl =35.5, H =1.0.) (2mks)

  1. A gaseous hydrocarbon of empirical formula CH2 occupies a volume of 6000cm3 at room temperature and pressure and weighs 7g (1mol of a gas occupies 24000cm3).

a) Calculate the number of moles of the hydrocarbon in 6000cm3 of the gas.(2mks)

b) Determine the molar mass(mass of one mole) of the gas(1mk)

c) Find the molecular formula of the gas.(2mks)

  1. Determine the mass of copper that contains as many atoms as there are molecules in 4g of oxygen gas(CU =64, O =16). (3mks)

(d) When vaporized, 0.1g of Q occupies 25cm3 at s.t.p (i) Calculate the relative molecular mass of Q (2mks)

(ii) Determine the molecular formula of Q(2mks)

  1. How many grams of magnesium would react with excess aqueous hydrochloric acid to produce 1.2 litres of hydrogen gas at room temperature? (2mks)
  1. The average concentration of potassium ions (K+) in blood serum is 0.195g/1. What is the concentration in moles per litre (2mks)

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