Explain why commercial indicators are preferred to flower exacts as acid-base indicators.
Explain why it is important to put off a non-luminous flame immediately after use.
You are provided with the following: thermometer, boiling tube, beaker, Bunsen burner, pure substance X whose boiling point is about 80°C, water and any other apparatus that may be required. Draw a labelled diagram of the set-up that can be used to determine the melting point of X.
Study the set-up in Figure 6 and answer the questions that follow.
(a) Name the substance that was collected in tube p.
(b) Write an equation for the reaction which occurs in tube Q in the first few minutes of the experiment.
(c) Give a suitable Conclusion for the experiment in the set-up.
Using iron filings, describe an experiment that can be conducted to show that oxygen is present in air.
An experiment was Carried out to determine the presence of Substances P, Q, R and S in mixture T. The results obtained are shown in Figure 2.
(a) Ne the method of separation illustrated in Figure 2.
(i) one Substance Which Contains a Component not present in T.
(ii) a substance which is least Soluble in the solvent used.
Describe an experiment to show that group one elements react with cold water to form alkaline Solutions
(a) A student used Figure 2 to investigate the action of dilute sulphuric(VI) acid on some metals. Beaker I and II contained equal volumes of dilute sulphuric(VI) acid. To beaker I, a clean iron rod was dipped and to beaker II, a clean copper rod was dipped.
(i) Why was it necessary to clean the metal rods?
(ii) Describe the observations made in each beaker.
(iii) Explain the observations in (a) (ii).
(b) Figure 3 shows the apparatus used to burn hydrogen in air. Use it to answer the questions that follow.
(i)State the role of substance X.
(ii) Give the name of the substance that could be used as X.
(iii) State the role of the suction pump.
(iv) Name the product Y formed.
(v) Give a simple physical test to prove the identity of Y.
vi) State the difference between 'dry' and 'anhydrous'.
(a) (i) To remove oxide layer on the metal.
(ii) Beaker I :
. Bubbles of a colourless gas / effervescence ;
. Solution turns green;
. the size of iron rod decreases
. The solution remained colourless.
. No bubbles/effervescence
Iron is more reactive than hydrogen hence it reacts with sulphuric(VI) acid to
produce hydrogen gas and iron(III) sulphate which is green.
Copper is below hydrogen hence no reaction will take place.
(b) (i) To dry hydrogen gas.
(ii) Calcium oxide /anhydrous calcium chloride /silica gel.
Explain how a student can establish whether a liquid sample extracted from a plant is pure.
The flow chart in Figure 3 shows the process of obtaining a sample of nitrogen gas. Study it and answer the questions that follow.
(a) Identify X
(b) Write an equation for the reaction with heated copper turnings.
(c) Name an impurity in the sample of nitrogen gas.
Using the elements chlorine, calcium and phosphorus:
(a) Select elements that will form an oxide whose aqueous solution has a pH less than 7.
(b) Write an equation for the reaction between calcium oxide and dilute hydrochloric acid.
(c) Give one use of calcium oxide.
Potassium nitrate liberates oxygen gas when heated. Draw a diagram of a set-up that shows heating of potassium nitrate and collection of oxygen gas.
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.
Describe an experimental procedure that can be used to extract oil from nut seeds.
Crush grind using a pestle and mortar, add suitable solvent of propanone ethanol alcohol and stir to dissolve oil. Filter the mixture to obtain a solution of the oil. Leave the solution in the sun for propanone to evaporate leaving the oil.
Given the following substances: wood ash, lemon juice and sodium chloride.
(a) Name one commercial indicator that can be used to show whether wood ash, lemon juice and sodium chloride are acidic, basic or neutral.
(b) Classify the substances in 15(a) above as acids, bases or neutral.
(b) Wood ash- Basic
Lemon Juice - acidic
Sodium Chloride- neutral
Maurice Atika is a teacher and a netprenuer.