i) An element is a substance which cannot be split into any simpler substance by any chemical process
ii) Atomic number is the number of protons in an atom
johnmulu answered the question on February 2, 2017 at 07:27
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What are isotopes?
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What are isotopes?
Date posted:
February 2, 2017
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Why is calcium more reactive than beryllium?
(Solved)
Why is calcium more reactive than beryllium?
Date posted:
February 2, 2017
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Write the electronic configuration of calcium (atomic number 20) and beryllium (atomic number 4)
(Solved)
Write the electronic configuration of calcium (atomic number 20) and beryllium (atomic number 4).
Date posted:
February 2, 2017
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With reference to atomic number of one, explain why hydrogen can be placed in either group I and VII of the periodic table
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With reference to atomic number of one, explain why hydrogen can be placed in either group I and VII of the periodic table.
Date posted:
February 2, 2017
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The electron arrangement of ions X3+ and Y2- are 2,8 and 2,8,8 respectively
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The electron arrangement of ions X3+ and Y2- are 2,8 and 2,8,8 respectively
a) Write the electronic arrangement of the elements X and Y
b) Write the formula of the compound that would be formed between X and Y
Date posted:
February 2, 2017
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Answers (1)
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When a candle was burnt completely, the total mass of products was found to be greater than the original mass of the candle. Explain
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When a candle was burnt completely, the total mass of products was found to be greater than the original mass of the candle. Explain
Date posted:
February 2, 2017
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Answers (1)
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A candle wax is mainly a compound consisting of two elements. Name the two elements
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A candle wax is mainly a compound consisting of two elements. Name the two elements
Date posted:
February 2, 2017
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Answers (1)
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In an experiment, a piece of magnesium ribbon was cleaned with steel wool. 2.4 g of the clean magnesium ribbon was placed in a crucible and completely burnt in oxygen
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In an experiment, a piece of magnesium ribbon was cleaned with steel wool. 2.4 g of the clean magnesium ribbon was placed in a crucible and completely burnt in oxygen. After cooling, the product weighed 4.0 g
a) Explain why it was necessary to clean the magnesium ribbon
b) What observation was made in the magnesium ribbon
c) Why was there an increase in mass
Date posted:
February 2, 2017
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Answers (1)
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When wood is burnt, a grey powder called ash remains. The ash is stirred with water and filtered a colourless solution is obtained
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When wood is burnt, a grey powder called ash remains. The ash is stirred with water and filtered a colourless solution is obtained
a) What is the main component of the colourless solution
b) Explain your answer in (a) above
c) State the observation that would be made if methyl orange indicator was passed through the solution of ash.
Date posted:
February 2, 2017
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Answers (1)
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Name another gas which used together with oxygen in welding
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Name another gas which used together with oxygen in welding
Date posted:
February 2, 2017
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When magnesium metal is burnt in air, it reacts with both oxygen and nitrogen gases giving a white ash
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When magnesium metal is burnt in air, it reacts with both oxygen and nitrogen gases giving a white ash. Write two equations for the reactions that take place
Date posted:
February 2, 2017
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Explain how you would separate a mixture of nitrogen and oxygen gases given that their boiling points are
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Explain how you would separate a mixture of nitrogen and oxygen gases given that their boiling points are - 196o C and - 183o C
Date posted:
February 2, 2017
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(a) Name a suitable solvent for extracting an indicator from flowers (b) Give a reason why the solvent named in (a) above is used
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a) Name a suitable solvent for extracting an indicator from flowers
b) Give a reason why the solvent named in (a) above is used
Date posted:
February 2, 2017
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Answers (1)
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Describe how pH of anti-acid (Actal) powder can be determined in the laboratory
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Describe how pH of anti-acid (Actal) powder can be determined in the laboratory
Date posted:
February 2, 2017
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Starting with red roses, describe how (i) a solution containing the red pigment may be prepared
(Solved)
Starting with red roses, describe how;
i) a solution containing the red pigment may be prepared
ii) The solution can be shown to be an indicator
Date posted:
February 2, 2017
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When a student was stung by a nettle plant, a teacher applied an aqueous solution of ammonia to the affected area
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When a student was stung by a nettle plant, a teacher applied an aqueous solution of ammonia to the affected area of the skin and the student was relieved of pain. Explain
Date posted:
February 2, 2017
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Answers (1)
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The pH of a sample of soil was found to be 5.0. An agricultural officer recommended the addition of calcium oxide in the soil
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The pH of a sample of soil was found to be 5.0. An agricultural officer recommended the addition of calcium oxide in the soil. State two functions of the calcium oxide in the soil
Date posted:
February 2, 2017
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10g of sodium hydrogen carbonate were dissolved in 20 cm3 of water in a boiling tube. Lemon juice was then added dropwise with shaking unit there was no further observable change
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10g of sodium hydrogen carbonate were dissolved in 20 cm3 of water in a boiling tube. Lemon juice was then added dropwise with shaking unit there was no further observable change
a) Explain the observation which was made in boiling tube when the reaction was in progress
b) What observation would have been made if the lemon juice had been added to copper turning in a boiling tube? Give a reason
Date posted:
February 2, 2017
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Answers (1)
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A mixture contains ammonium chloride, copper (II) oxide and sodium chloride. Describe how each of the substances can be obtained from the mixture
(Solved)
A mixture contains ammonium chloride, copper (II) oxide and sodium chloride. Describe how each of the substances can be obtained from the mixture
Date posted:
February 2, 2017
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Answers (1)
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Iron (III) oxide was found to be contaminated with copper (II) sulphate. Describe how a pure sample of iron (III) oxide can be obtained
(Solved)
Iron (III) oxide was found to be contaminated with copper (II) sulphate. Describe how a pure sample of iron (III) oxide can be obtained.
Date posted:
February 2, 2017
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Answers (1)