CHEMISTRY EXAM QUESTIONS| FIRST TERM EXAMINATION, 2018/2019 SESSION

CHEMISTRY EXAM QUESTIONS| FIRST TERM EXAMINATION, 2018/2019 SESSION

CLASS: SS1       SUBJECT:  CHEMISTRY      TIME: 2 HOURS

SECTION A – OBJECTIVES [50MARKS]

Instructions: Answer all questions

1. Chemistry can be applied in the following fields EXCEPT A. Agriculture Oil and gas  C. Politics  D. Metallurgy
2. Separation of mixtures of solids with various sizes can be done
3. Magnetic separation B. Coarsing C. Sublimation   D. Sieving
4. Which of the following is an example of a chemical change?
5. Dissolution of salt in water B. Rusting of iron C. Melting of ice
6. Separating of mixture by distillation
7. These are basic particles from which matter could be made EXCEPT
8. Salt B. Atoms C. Ions   D. Molecules
9. A molecule of neon is A. Diatomic Ionic  C. Triatomic  D. Minoatomic
10. Which of these requires crystallization most? A. Drug making Cement making  C. Paint making  D. Perfume making
11. Which one is the odd-one out? A. Air Urine  C. Brass  D. Sand
12. Chemical hypothesis is different from chemical law that A. Hypothesis is not reasonable explanation to observation made while law is reasonable Hypothesis is a reasonable explanation to observations while law is a statement from a scientist   C. Hypothesis is a reasonable explanation to observations while law is a statement which confirms the hypothesis after extensive tests  D. None of the above
13. Separating funnel is used for separating a mixture of A. Liquids with different boiling points  Liquids with sediment  C. Liquids with different colour  D. Liquids that are immiscible
14. The simplest unit of water that retains its properties is called? An atom   B. An element  C. An hydroxide   D. A molecule
15. Of the basic particles that make up an atom, the one with the smallest mass is A. A proton A neutron   C. An     D. An electron
16. The atomic mass of an element is mostly due to the mass of A. Electrons and protons Electrons and neutrons  C. Protons and neutrons
17. Positions and neutrons
18. One of the following is NOT a branch of chemistry Analytical chemistry   B. Medicinal chemistry  C. Organic Chemistry  D. Hybrid chemistry
19. One of these professions has no need for chemistry A. Mining
20. Engineering C. Philosophy D. Geology
21. How many molecules are there in 1 mole of chlorine molecules? A. 35.5 molecules 6.02 x 10^-23 molecules  C. 17.0 molecules  D. 6.02 x 23 molecules
22. A heterogeneous mixture can be defined as any mixture A. Whose compositions combine to produce a uniform substance Whose compositions combine to produce a non-uniform substance  C. Formed by solids and liquids  D. Of a solute and a solvent
23. Atomicity of Ozone is A. 1 2    C. 3   D. 4
24. The relative molecular mass of Lead (ii) trioxonitrate (v) is? (Pb = 207,

N = 14, O = 16) A. 170  B. 222   C. 232  D. 132

19. The percentage of oxygen in sulphur(iv) oxide is (S = 32, O=16) A. 5%   50%   C. 500%   D. 25%
20. The empirical formula of C_6­H₆ is CH  B. C₃H₃   C. C₆H₆   D. 3CH
21. Which of the following techniques can be used to obtained ethanol from a mixture of ethanol and water? A. Boiling Chromatography
22. Crystallization D. Distillation
23. What is the relationship between empirical formula and molecular formula? A. Empirical formula = Molecular formula Empirical formula  = n x molecular formula (n=1,2,3…)   C. Molecular formula = n x Empirical  formula (n = 1, 2,3…) D. Molecular formula x Empirical  formula = 1
24. Based on the IUPAC way of representing symbols, the symbol for Iron is A. He   Ir    C. Ion  D. Fe
25. Calculate the percentage by mass of Lead in 1 mole of P_b (NO₃)₂

(P_b = 207; N = 14, 0 = 16) A. 76.9%   b. 62.5%   C. 77.5%   D. 87.3%

25. How many moles of magnesium atoms are present in 0.80g of magnesium? (Mg = 24) A. 0.003mole 0.30mole  C. 0.33mole
26. 0.03mole
27. Modern standard element with which chemists define relative atomic mass  is A. ¹²C    ¹³C    C. ³H   D. ¹⁴C
28. Which of the following are mixtures? (i) Petroleum (ii) Rubber latx  (iii) Vulcanizers solution (iv) carbon (ii) sulphur  i, ii and iii   B. i, ii and iv   C. i  and iii only  D. i  and iv
29. Which of the following substances is NOT a homogenous mixture?
30. Filtered seawater B. Soft drink c. Flood water   D. writing ink
31. Fractional crystallization is a method of separating A. Crude oil
32. Liquid-liquid mixture C. coal D. solids of different solubilities in a liquid
33. There are three main states of matter; liquid, solid, and gas. All have different properties. Which statement describes the physical state of a solid but not a liquid or gas? A. It has its own shape It does not have its own shape  C. It takes the shape of its container   D. It changes shape with temperature
34. Which of the following is a property of both liquids and gases, but not solids? A. Can flow Can be compressed  C. Has a definite shape
35. Has a definite texture
36. Chemical symbol represents A. Chemical formula Molecular formula  C. Structural formula  D. Atomic formula
37. A modern model of an atom show that electrons are present outside the nucleus in region of highest A. Probability Velocity  C. Speed
38. Energy level
39. Smaller particles in an atom are called A. Atomic particles Subatomic particles  C. Smaller particles  D. Neutral particles
40. At room temperature, helium does Not have a definite shape or volume. Which state is it in? A. Gas  Solid  C. Water  D. Liquid
41. Which property determines whether one substance will sink or float in another substance? A. Texture Density  C. Volume   D. Temperature
42. The water supply system in your town is contamin with salt water. Drinking water can be obtained from the contaminated water by A. Filtration Evaporation  C. Crystallization  D. Distillation
43. Which of the following methods would you recommend to recover Iron pieces from a garbage dump containing dry leaves, papers and broken glass? A. Burning of leaves and paper  Filtration  C. Hand picking of iron pieces  D. Magnetic separation
44. The criteria to verify the purity of a solid substance are I. Boiling point Melting paint  III. Density  IV. Refractive Index  A. I, II   B. II, III  C. I, II, III  D. I, IV
45. Valency is the combining power of an element. The valency of Nitrogen is A. 1 2     C.3   D. 2 or 3
46. What is the mass in grammes of 0.50mole of oxygen atoms? (O= 16)
47. 0.50g B. 2.0g   C. 5.0g   D. 8.0g
48. The mass spectrometer is used to measure A. The number of protons in the nucleus of atom  The number of electrons in an atom  C. The relative molecular mass of an atom  D. Quantity of mass
49. A molecule of neon is A. N N₂  C. N_e  D. N_ez
50. One mole of oxygen atoms A. Has a molar mass of 32g Has 6.02 x 10²³ molecules  C. Can be represented as O₂   D. Contains Avogadro’s number of atoms
51. The constituents of a leaf pigment can be separated by
52. Chromatography B. Filtration C. Fractional crystallization
53. Fractional distillation
54. An element X with relative atomic mass 16.2 contains two isotopes with relative abundance of 90% and  with relative abundance of 10%. The value of m is A. 14   12   C. 18    D.16
55. What is the percentage of mass of sodium in sodium hydroxide (Na = 23, O = 16, H =1) A. 40.4%   42.5%  C. 57.2%  D. 73.0%
56. Neutral atoms of neon with atomic number 10 have the same number of electrons as A. 0^2- C_a²⁺   C. K⁺   D. S^2-
57. The modern way of representing symbols was developed in 1818 by
58. Einstein B. Berzelius C. Dalton   D. Rutherford
59. In countries where temperatures are most times far below zero, why is common salt sprinkled on the icy-roads? A. To remove impurities  To lower the melting point of the ice

SECTION B – THEORY

Instruction: This section is divided into two parts. Attempt only ONE question in part I and any THREE (3) questions in Part II

PART I [40MARKS]

1. Using a neat diagram, explain how a mixture of two immiscible liquids of your choice can be separated.

2a.     Define the terms (i) mixture  (ii)compound. Give three differences between them

1. Classify the following substances as an element, a mixture or a compound (i) Limestone (ii) Diamond  (iii) Sand (iv) Soil (v) Urine (vi) Bronze  (vii) Sugar (viii) Gold   (ix) Clay  (x) Urea  (xi) Antimony   (xii) Soap (xiii) Milk  (xiv) Air  (xv) Neon  (xvi) Iron
2. Why is sodium chloride solution regarded as a mixture?
3. How would you separate the components of the following mixtures?

(i) A mixture of sodium chloride and ammonium chloride  (ii) A mixture of Iron dust and zinc dust  (iii)A mixture of water and sugar

(iv) A mixture of two solids which have widely different solubilitus in water  (v) A pure solid from a concentrated solution of its salt.

PART II  [ 60 MARKS]

 State Dalton’s atomic theory and its corresponding modification

4a.     How is a Homogenous mixture different from a Heterogeneous mixture?

1. Classify each of the following changes as either a physical change or a chemical change

(i)       The addition of water to quicklime

(ii)      The melting of candle ware

(iii)     The change in colour of zinc oxide from white to yellow when

Heated

(iv)     The hardening of cement by the absorption of carbon(iv) oxide

(v)      The addition of a base to an acid to form salt and water only

5a.     Define the relative atomic mass of an element

1. Calculate the relative molecular mass of;
2. Slaked lime, Ca(OH)₂
3. Sodium trioxonitrate(v), N_a­NO­₃

iii.      Hydrated copper(ii) tetraoxosulphate(vi), CuSO₄ – 5H₂O

1. What do you understand by the atomicity of an element?

(Ca = 40; O = 16;  H=1; Na = 23; N = 28; S = 32; Cu = 64)

6. Find the empirical formula of a compound which on analysis yields the following as the reacting masses. Carbon = 2.0g, hydrogen = 0.34g, Oxygen = 2.67g. from your result, find the molecular formula of the compound, if its relative molecular mass is 60.

7a.     Define the following

(i) Mole   (ii) Molecule   (iii) Iron   (iv) atom

1. How many moles are there in 20g of CaCO₃?
2. Calculate the percentage by mass of nitrogen in trioxonitrate(v) acid