User:Geraldndongawachira/sandbox

1. Give two reasons why Helium is preferred to hydrogen in raising weather balloons. (2mks) 2. Describe how the mixture of sodium chloride, iodine and copper (II) oxide can be separated . (3mks) 3. The set up below was used to investigate two properties of hydrogen gas. a) State and explain two observations made in the combustion tube (1mk) b) Explain why i) The combustion tube is placed in a slanting position. (1mk) ii) Unreacted hydrogen gas is burnt at tube K. (1mk) iii) A stream of hydrogen gas is passed through the combustion tube before heating copper (II) (1mk) 4. Describe how oxygen gas is obtained from air. (4mks) 5a) What is a flame (1mk) b) Explain why i) Non luminous is hooter than luminous flame. (1mk) ii) Luminous flame produce soot and light. (1mk) 6a) What is meant by the term i) Atomic number (1mk) ii) An element. (1mk) b) An ion of magnesium is represented as 24 12 Mg2+. How many protons, neutrons and electrons does the ion have. (3mks) 7a) What is neutralization? b) Give two reasons why calcium oxide is added to acidic soils. c) Describe how the PH of actal can be determined in the laboratory. (3mks) 8. Write and complete the following word equations. a) Magnesium and dilute hydrochloric acid. (1mk) b) Phosphorous and scarce oxygen gas. 9. An element X has two isotopes X and X. The two isotopes occur in the ratio of 3:1 respectively. (1mk) a) What are isotopes. (1mk) b) Calculate the relative atomic mass of X. (2mks) 10a) Oxygen gas is prepared by reacting manganese (iv) oxide with liquid L. a) Name liquid L. (1mk) b) Write the word equation for the reaction that occurs. (1mk) c) Describe the chemical test for oxygen gas. (1mk) 11a) State the kinetic theory of matter. b) State two criterion of purity. 12a) Distinguish between rusting and corrosion. b) State two factors that accelerate rusting. 13. The set up below was used to separate two immiscible liquids A and B. Density of A is 1.0g/cm3 while that of B is 0.85g/cm3 a) Which liquid is collected first. Explain (2mks) b) Name apparatus C. (1mk) c) Give two properties that enables the liquid to be separated. (2mks) 14a) What is an alkali? b) Write a word equation for the reaction between. i) Sodium hydroxide and dilute sulphuric VI acid. ii) Magnesium and Nitrogen.