Chemistry Paper 1 Form 3 End Term 2 Exams 2021 with Marking Schemes
Questions
- The diagram below shows Chromatograms for five different dyes.
- Name one condition required to separate the chromatograms present in a dye. (1 mk)
- What is meant by the solvent front? . (1 mk)
- Which chromatograms are present in dye E. (1 mk)
- Name two industrial applications of chromatography. (2 mks)
- An element Y has the electronic configuration 2.8.5
- Identify its period __________ (1mk)
- Write a formula of the most stable anion formed when U ionizes. (1mk)
- Explain the differences between the atomic radius of element Y and its ionic radius. (2mks)
-
- What is meant by allotropy? (1 mark)
- The diagram below shows the structure of one of the allotropes of carbon
- Identify the allotrope (½mk)
- State one property of the above allotrope and explain how it is related to its structure. (1½mk)
- Study the flow chart below and answer the questions that follow.
- Identify the metal oxide. (1mk)
- Write an ionic equation leading to the formation of the white precipitate X. (1mk)
- Give the formula of the ions responsible for the colourless solution Y. (1mk)
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- Apart from their location, state any two differences between a proton and an electron.(2 mks)
- Protons and neutrons are found in the nucleus of an atom. State two important roles played by of neutrons in the nucleus of an atom. (2 mks)
- Give equations to show the reactions that take place when;
- Iron reacts with steam. (1 mark)
- Name and give one industrial use of the gas produced in the reactions in (i) above. (2mks)
Name:
Use:
- 20cm3 of an unknown gas Q takes 12.6 seconds to pass through small orifice.10cm3 of oxygen gas takes 11.2 seconds to diffuse through the same orifice under the same conditions of temperature and pressure. Calculate the molecular mass of unknown gas Q (O=16). (3mks)
- A compound of carbon, hydrogen and oxygen contains 71.12g by mass of oxygen, 2.2g hydrogen and the rest is carbon. It has relative molecular mass of 90.
- Determine the empirical formula of the compound. (3mks)
- Determine the molecular formula of the compound. (2mks)
- Study the information in the table and answer questions that follow:
- Determine the number of neutrons of R1 (1mk)
- Calculate the relative atomic mass of element R. (2mks)
-
- Identify the type of bond formed in (i) and (ii). (1mks)
(I)…………………………………………………..
(II)………………………………………………….. - Use dot (.) and cross (x) diagram to draw the structure of Sulphur (IV) oxide. ( 2marks)
- Identify the type of bond formed in (i) and (ii). (1mks)
- Complete the table below. (3 mks)
-
- State Gay Lussac’s law. (1mk)
- What volume of oxygen will be required for complete combustion of 100cm3 of carbon (II) oxide. What is the volume of the product formed (All volumes at same temperature and pressure). (2mks)
- If 25.0cm3 of 0.1 M H2SO4 solution neutralized a solution containing 1.06g of sodium carbonate in 250cm3 of solution, calculate the molarity and volume of the sodium carbonate solution used. (3mks)
-
- State Charles’ law. (1mk)
- The capacity of a balloon to hold a gas at 5oC is 1dm3 before it bursts due to expansions show whether it will burst or not at 35oC at constant pressure. (2mks)
- What is the colour of the following?
Metal oxide Colour when hot Colour when cold Zinc oxide (i) (ii) Lead (II) oxide (iii) (iv) - Form two students from Anestar Premier High School reacted three elements as shown in the table below
Element Reaction with oxygen Reaction with water X Formed acidic oxide No reaction Y Formed basic oxide Formed soluble hydroxide
Gave off hydrogen gasZ Formed acidic oxide Dissolved to form an acidic solution
Which element (s) is likely to be: (3mks)- Non-metal (s)
- Metal (s)
- Insoluble in water
- State the function of the following parts of a Bunsen burner (3mks)
- Air hole
- Collar
- Base
- Study the flow chart below and answer the questions that follow
- Identify gas X (1mk)
- Write an equation for the reaction between ammonia and gas X (1mk)
- Write an equation to show the formation of G and J (1mk)
- The diagram below shows the effect of sunlight on chlorine water
- Identify gas W (1mk)
- Write an equation to show the formation of gas W (1mk)
- What compounds are present in chlorine water? (1mk)
- Which compound is left in the beaker after complete formation of gas W? (1mk)
- Study the table below and answer the questions that follow
Element Atomic number Atomic radius Ionization energy K 3 0.089 1800 V 11 0.136 1450 T 19 0.174 1150 - Define the term ‘ionization energy’ (1mk)
- Explain the trend in the ionization energy from element K to T (2mks)
- Compare the trend in the melting and boiling points of elements K and T. (2mks)
- Explain using chemical means how you would differentiate between carbon (II) oxide and carbon (IV) oxide. (2mks)
- The following diagram shows the effect of electric current on lead (II) Chloride.
- When the circuit was completed no current flowed. Explain why. (1mk)
- When lead (II) Chloride was heated to about 3000C, it melted and there was light on the bulb. State and explain the observation made at the anode. (2mks)
- The set-up below shows the products formed when solid lead (ii) nitrate is heated.
- Identify:
- Liquid X …………………………………………………………… (1 mark)
- Gas Y…………………………………………………………… ( 1 mark)
- When lead (ii) Nitrate crystals are heated, they decrepitate and decompose, what is meant by the term decrepitating? (1 mark)
- Identify:
- Calculate the number of Al3+ ions released when 30cm3 of 0.1M of Aluminium Sulphate is dissolved in water. (L = 6.024 x 1023). (3mks)
Marking Scheme
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- – The chromatogram must have different solubility rate. (1 mk)
- The dyes must have different adsorption on the filter paper. (1 mk) - – It is the furthest distance reached by the solvent on the adsorbent material (or filter paper). (1 mk)
- It is indicated as H on the diagram. (1 mk) - Red, blue and green. (1 mk) (if only two are correct)
- D and A
- – Detecting and identifying poisonous substances present in food substances. (1 mk)
- Separation of dyes into pure colours. (1 mk)
- – The chromatogram must have different solubility rate. (1 mk)
-
- Period 3
- Y3-
- Ionic radius is large because incoming electrons repelled by energy levels.
-
- Existence of a substance in two or more forms without a change of state (1 mk)
-
- Graphite(½ mk)
- Conducts electricity, (1 mk) contains delocalised electrons. (½ mk) OR soft and slippery (1 mk) Hexagonal layer are held together by weak van der waals forces(½mk)(total 3 marks)
-
- Zinc oxide
- Zn2+(aq) + 2OH-(aq) → Zn(OH)2(s)
- Zn(NH3)42+
-
- Apart from their location, state any two differences between a proton and an electron. (2 marks)
- A proton is positively charged whereas an electron is negatively charged.
The mass of a proton is/atomic mass units whereas that of an electron is a.m.u
- A proton is positively charged whereas an electron is negatively charged.
- Protons and neutrons are found in the nucleus of an atom. State two important roles played by of neutrons in the nucleus of an atom. (2 mks)
- Prevent repulsion between the positively charged protons.
- Provide weight hence stability of the atom
- Apart from their location, state any two differences between a proton and an electron. (2 marks)
- Give equations to show the reactions that take place when;
- iron reacts with steam. (1 mark)
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g) - Name and give one industrial use of the gas produced in the reactions in (i) above. (1mk
- Hydrogen.
Uses: (Any one ) - Industrial manufacture of hydrochloric acid
- Industrial manufacture of Ammonia
- Used in weather balloons
- Hydrogen.
- iron reacts with steam. (1 mark)
-
Elements
C
H
O
% mass
No. of moles
Ratio of moles
No. of atoms
26.7
26.7/12 = 2.225
2.225/2.2 =1
1
2.2
2.2/1 = 2.2
2.2/2.2 = 1
1
71.1
71.1/16 = 4.44375
4.44375/2.2 = 2
2
Empirical formula CHO2
Molecular formula = (CHO2) n = 90
= (12+1+32) n =90
= (45) n = 90
45 45
= n=2
= C2H2O4 -
- 69 -31 = 38
- R.A.M of R = (61.3 x 69) + (38.7 x 71)
100
= 69.774
-
-
- Dative covalent bond
- Covalent bond
-
- – Lead; Pb;
- Cuprum;
- Kalium;
- Sternum -
- State Gay Lussac’s law. (1mk)
- When gases combine they do so in volumes that bears simple ratio to one another and to the product if it is gaseous.
- What volume of oxygen will be required for complete combustion of 100cm3 of carbon (II) oxide. What is the volume of the product formed ( All volumes at same temperature and pressure) (2mks)
2CO(g) + O2(g) → 2CO2(g) (1 mk)
100 50 100 volume of product = 100 cm3 (1 mk)
- State Gay Lussac’s law. (1mk)
- Moles of acid = 25 x 0.1
1000 = 0.0025.
Moles of Na2CO3 = 0.0025 mol since mole ratio = 1:1
Moles of Na2CO3 in 1000 cm3 = 1.06 x 1000 = 4.24g
250
Molarity = 4.24 = 0.04
106
Ma x va = mol of a
Mb x Vb mol of b
Vb = 0.1 x 25
0.04
62.5cm3 -
- the volume of a given mass of gas is directly proportional to its absolute temperature at constant pressure.
- V1= V2
T1 T2
V2 = 1 x 308 = 1.108dm3
278
The balloon will burst; at 35oC since volume is more than 1 dm3.;
-
- Yellow;
- White;
- Red-brown;
- Yellow;
-
- Z or X
- Y
- X
-
- To allow air to pass through;
- To regulate the amount of water entering through the air hole;
- To support the Bunsen burner;
-
- Oxygen;
- 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
- 2NO2(g) + H2O(l) → HNO2(aq) + HNO3(aq)
-
- Oxygen
- 2HOCl(l) → 2HCl(aq) + O2(g)
- Chloric (I) acid and hydrochloric acid
- hydrochloric acid
-
- Ionization energy is the minimum amount of energy required to remove an electron from the last energy level of an isolated neutral atom form a positively charged ion in gaseous state.
- The ionization energy decreases from K to T; this is because of the addition of an extra energy level from K to T which decreases the nuclear attraction hence easy to remove an electron from the outermost energy level;
- Group I; they all have one electron in their outermost energy level;
- Both K and T have giant metallic structures. K has smaller atomic/ionic size with strong metallic bonds that require higher amount of energy to break hence high melting and boiling point compared to T.
- Pass both gases through lime water; carbon (IV) oxide forms a white precipitate while carbon (II) oxide does not;
- The following diagram shows the effect of electric current on lead (II) Chloride.
- When the circuit was completed no current flowed. Explain why. (1mk)
- Solid lead (ii) chloride does not conduct electricity for there are no mobile ions
- When lead (II) Chloride was heated to about 3000C, it melted and there was light on the bulb. State and explain the observation made. (2mks)
- Bubbles (1 mk) of yellow green –chloride ions(1 mk) migrate to the anode and are discharged to form chlorine gas.
- On the diagram, indicate the anode and the cathode. (1mk)
- When the circuit was completed no current flowed. Explain why. (1mk)
- The set-up below shows the products formed when solid lead (ii) nitrate is heated.
- Identify:
- Liquid X
- Dinitrogen tetra – oxide (1 mark)
- Gas Y
- Oxygen … ( 1 mark)
- Liquid X
- When lead (ii) Nitrate crystals are heated, they decrepitate and decompose, what is meant by the term decrepitating? (1 mark
- Production of cracking noise when heated
- Identify:
- Calculate the number of Al3+ ions released when 30cm3 of 0.1M of Aluminium Sulphate is dissolved in water. (L = 6.024 x 1023). (3mks)
Al2(SO4)3(aq) → 2Al3+(aq) + 3SO42-(aq)
Moles of Al2(SO4)3
0.1 moles → 1000 cm3
? = 30 cm3
0.1 × 30 = 0.003 moles
1000
From mole ratio
Moles of Al3+ = 0.003 x 2
= 0.006 moles ✓ ½
No. of ions = 0.006 x 6.024 x 1023
= 3.6144 x 1021 ✓ ions
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