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Form 4 Acids, Bases and Salts Topical Questions and Answers

In this session, several questions on acids, bases and salts will be solved. All answers are well explained and in video format. Very ideal for those preparing for KCSE exams.

Lessons (66)

• 1.    In an experiment, soap solution was added to three separate samples of water. The table below shows the volumes of the soap solutions required to form lather with 1000cm3 of each sample of water before and after boiling. (a) Which water sample is likely to be soft? Explain. (b) Name the cause of change in the volume of soap solution used in sample III
  6m 24s

• 2.    The table shows how solubility of some substances in water varies with temperature. Which of the above substances is likely to be a gas? Explain
  2m 54s

• 3.    Explain the following observation. Chloride dissolves in water to form an electrolyte while the same chloride dissolves in methylbenzene to form a non-electrolyte.
  3m 10s

• 4.    The flow chart below show an analysis of a mixture R that contains two salts. Study the analysis and answer the questions that follow. (a)(i) What condition is necessary for the process in step I to take place. (ii) Draw a labeled diagram for the set-up that could be used to separate the mixture formed in step II. (iii) Write an ionic equation for the reaction between the cation in filtrate x and
  20m 13s

• 5.    Study the chart below and answer the questions that follow: (a) Identify: (i) The metal ions in solution K (ii) The white precipitate L (b) What property of the white precipitate L is illustrated by step I and II?
  5m 47s

• 6.    (a) Give the name of each of the processes described below which takes place when salts are exposed to air for sometime. (i) Anhydrous copper sulphate become wet. (ii) Magnesium chloride forms an aqueous solution . (iii) Fresh crystals of sodium carbonate, #Na_2CO_3#.#10H_2O#, become covered with white powder of formula,# Na_2CO_3.H_2O# (b) Write the formula of the complex ion formed in each of
  18m 6s

• 7.    In an equation below, identify the reagent that acts as a base. Give a reason
  4m 9s

• 8.    Study the scheme below and answer the questions that follows. (a) Write the formula of the cation present in solution F. (b) What property of chlorine is shown in step I. (c) Write an equation for the reaction which occur in step III.
  6m 46s

• 9.    90#cm^3# of 0.01M calcium hydroxide were added to a sample of water containing 0.001 moles of calcium hydrogen carbonate. (a) Write an equation for the reaction which took place (b) Calculate the number of moles of calcium ions in 90#cm^3# of 0.01M calcium hydroxide. (c) What would be observed if soap solution was added dropwise to a sample of the water after the addition of the calcium hydroxide
  6m 28s

• 10.    (a) Give the formula of an oxide which reacts with both dilute hydrochloric acid and hot concentrated sodium hydroxide (b) Give the formulae of the products formed when oxide in (a) above reacts with excess hot concentrated sodium hydroxide
  5m 0s

• 11.    Study the information in the table and answer the question below the table. Describe how a solid sample of substance A could be obtained from a solid mixture of A and B
  1m 47s

• 12.    A sample of water drawn from a river passing through an agricultural district was divided into two portions. The first portion gave a white precipitate when acidified barium chloride was added. The second portion when warmed with aqueous sodium hydroxide gave a colourless gas which turned a moist red litmus paper blue. (a) Identify the ions present in the river water. (b) Suggest the possible
  4m 46s

• 13.    Distinguish between a strong and a weak acid. Give an example of each.
  2m 52s

• 14.    The scheme below shows some reaction sequence starting with solid N. (a) Identify solid N (b) Write the formula of the complex ion present in solution Q
  4m 19s

• 15.    A bee-keeper found that when stung by a bee, application of a little solution of sodium hydrogen carbonate helped to relieve the irritation from the affected area. Explain.
  1m 59s

• 16.    (a) The column below was used to soften hard water. (i) Explain how hard water was soften as it passed through the column. (ii) After sometime the material in the column is not able to soften hard water. How can the material be reactivated? (b) Give one advantage of using hard water for domestic purposes.
  3m 51s

• 17.    Study the flow chart below and answer the questions that follow (a) Name (i)the reagent used in step I (ii) Compound A (b) Write an ionic equation for the reaction in step IV
  7m 10s

• 18.    The table below shows the solubility of a salt at various temperatures What would happen if a sample of a saturated solution of the salt at #40^0C# is heated to# 80^0C#? Explain
  2m 18s

• 19.    State and explain one disadvantage of using hard water in boilers.
  1m 6s

• 20.    When solid magnesium carbonate was added to a solution of hydrogen chloride in methylbenzene, there was no apparent reaction. On addition of water to the resulting mixture, there was vigorous effervescence. Explain these observations.
  2m 56s

• 21.    The table below shows the PH values of solutions I, II, III and IV. (i) Which solution is likely to be that of calcium hydroxide? (ii) Select the solution in which a sample of aluminium oxide is likely to dissolve. Give a reason for your answer.
  2m 34s

• 22.    Study the solubility curves below and answer the question that follows. What happen when a solution containing 40g of potassium chlorate and 40g of potassium nitrate in 100g of water at #90^0C# is cooled at #40^0C#? Explain.
  2m 41s

• 23.    The table below shows the tests carried out on separate samples of water drawn from a well and the results obtained. (a) Identify the cation and the anion present in the water. (b) Write an ionic equation for the reaction which takes place in test (iii)
  2m 7s

• 24.    (a) A student was supplied with colourless liquid suspected to be water. (i) Describe two chemical test that could have been used to show that liquid was water. (ii) How could it have been shown that liquid was pure water? (b) The flow chart below shows the various stages of water treatment. Study it and answer the questions that follow. (i) Which substances are likely to be removed in filtration
  7m 53s

• 25.    Sample solutions of salts were labeled as I, II, III and IV. The actual solutions, not in that order , are lead nitrate, zinc sulphate, potassium chloride and calcium chloride. (a) When aqueous sodium carbonate was added to each sample separately, a white precipitate was formed in I, III and IV only. Identify solution II. (b) When excess aqueous sodium was added to each sample separately, a white
  11m 30s

• 26.    a) State one cause of temporary hardness in water. (b) How does distillation remove hardness from water.?
  1m 8s

• 27.    (a) Study the information in the table below and answer the questions that follow. (the letter do not represent the actual symbols of the elements) (i) What is the general name to the group in which elements P,Q, and R belong? (ii) What is meant by ionization energy? (iii) Explain why element P have the highest ionization energy. (iv) When a piece of element Q is placed on water it melts and a
  8m 57s

• 28.    The following tests were carried out on three separate portions of a colourless solution R. (a) From the information in test (i), name a cation which is not present in solution (b) Identify a cation, which is likely to be present in solution S (c) Write an ionic equation for the reaction which takes place in test(ii)
  3m 44s

• 29.    (a) What method can be used to separate a mixture of ethanol and propanol? (b) (i) Explain how a solid mixture of sulphur and sodium chloride can be separated into solid sulphur and solid sodium chloride. (ii) How can one determine if the solid sulphur is pure? (c) The table below give the solubilities of potassium bromide and potassium sulphate at #0^0C# and #40^0C# When an aqueous mixture
  7m 32s

• 30.    In an experiment equal amounts of magnesium powder were placed into a test-tube 1 and 2 as shown below Explain why the amount of hydrogen gas liberated in test-tube 2 is greater than in test-tube 1 before the reaction is complete.
  0m 44s

• 31.    The table below shows the tests carried out on a sample of water and the results obtained. (a) Identify the anion present in the water. (b) Write an ionic equation for the reaction in III. (c) Write the formula of the complex ion formed in II.
  1m 43s

• 32.    Starting with aluminium sulphate, describe how solid sample of aluminium hydroxide could be prepared.
  0m 31s

• 33.    In an experiment, a student put equal volumes of mixtures of ethanoic acid in water and ethanoic acid in hexane in two test-tubes as shown below. In each test-tube, equal amounts of solid sodium hydrogen carbonate were added. (a) State the observation which was made in each test-tube. (b) Explain the observation in (a) above.
  1m 26s

• 34.    Zinc oxide reacts with acids and alkalis. (a) Write the equation for the reaction between zinc oxide and: (i) Dilute sulphuric (VI) acid (ii) Sodium hydroxide solution (b) What property of zinc oxide is shown by the reaction in (a) above?
  1m 5s

• 35.    Equal volumesof 1M monobasic acids L and M were each reacted with excess magnesium turnings. The table below shows the volumes of the gas produced after one minute. Explain the differences in the volumes of the gas produced.
  1m 11s

• 36.    (a) Water from a town in Kenya is suspected to contain chloride ions but not sulphate ions. Describe how presence of the chloride ions in the water can be shown. (b) State one advantage of drinking hard water rather than soft water.
  0m 47s

• 37.    Besides is a list of oxides. #Mgo,N_2O, K_2O, CaO and Al_2O_3#. Select: (a) a neutral oxide (b) a highly water soluble basic oxide. (c) An oxide which can react with both sodium hydroxide solution and dilute hydrochloric acid
  1m 4s

• 38.    (a) Starting from solid magnesium oxide, describe how a solid sample of magnesium hydroxide can be prepared. (b) Give one use of magnesium hydroxide.
  0m 54s

• 39.    (a)Complete the table below to show the colour of the given indicator in an acidic and basic solutions. (b) How does the PH value of 0.1 M potassium hydroxide solution compare with that of 0.1 M aqueous ammonia? Explain.
  1m 38s

• 40.    (a) Explain why permanent hardness in water cannot be removed by boiling. (b) Name two methods that can be used to remove permanent hardness from water.
  0m 42s

• 41.    The table below shows the tests that were carried out on solid N and the observations made. Write a formula of the anion in; (a) Solid N (b) The colourless solution formed in test III.
  1m 13s

• 42.    (a) The elements nitrogen, phosphorous and potassium are essential for plant growth. (i) Potassium in fertilizers may be in the form of potassium nitrate. Describe how a sample of a fertilizer may be tested to find out if it contained nitrate ions. (ii) Calculate the mass of nitrogen present if a 25kg bag containing pure ammonium phosphate , #(NH_4)_2HPO_4#. (N= 14.0, H=1.0, P=31.0,O=16.0)
  4m 17s

• 43.    The table below gives the solubilities of substances J, K and L at different temperatures. Select the substances which, when dissolved in water, heat is given out. Give a reason.
  0m 55s

• 44.    A compound whose general formula is M(OH) reacts as shown by the equation below. #M(OH)_3(s) + OH^(-) (aq) to M(OH)_4(aq)# #M(OH)_3(s) + 3H^(+) (aq) to M^(3+) (aq) +3H_2O(l)# (a) What name is given to compounds which behave like M(OH)3 in the two reactions. (b) Name two elements whose hydroxides behave like that of M.
  0m 35s

• 45.    Hardness of water may be removed by either boiling or addition of chemicals. (a)Write an equation to show how boiling removes hardness of water. (b)Name two chemicals that are used to remove hardness of water.
  0m 39s

• 46.    The solubility curve of potassium nitrate is shown below. (a) Determine the solubility of potassium nitrate at #50^0C# (b) Determine the molar concentration of saturated potassium nitrate at #50^0C# (K=39.0;O=16.0; N= 14.0 and density of water #1 gcm^(-3)#)..
  2m 55s

• 47.    Use the flow chart below to answer the questions that follow. (a) What observation would be made in step I? (b) Name another substance that could be used in step 2. (c) Give the name of substance H.
  1m 51s

• 48.    For each of the following reactions, state the observation and write The formula of the compound responsible for the observation: (a) Bromine water is added to aqueous potassium iodide; (b) Excess aqueous ammonia is added to copper (II) hydroxide.
  1m 3s

• 49.    The curves below show how the electrical conductivity of hydrochloric and ethanoic acids vary with concentration. Explain why the electrical conductivity of 0.1M hydrochloric acid is higher than that of 0.01M ethanoic acid.
  0m 45s

• 50.    A sample of river water was divided into three portions. The table below shows the tests carried out on the portions and the observations made. Complete the table by filling in the inferences.
  2m 31s

• 51.    (a) What is meant by a strong acid? (b) In an experiment, 40 #cm^3# of 0.5 M hydrochloric acid was reacted with excess sodium carbonate and the volume of carbon (IV) oxide produced recorded with time. In another experiment, the same volume and concentration of ethanoic acid was alsoreacted with excess sodium carbonate and the volume of carbon (IV) oxide produced recorded with time.
  1m 53s

• 52.    Soap dissolves in water according to the equation below; #NaSt(aq) to Na^(+) (aq) + St^(-)# where #St^(–)# is the stearate ion. (a) Write the formula of the scum formed when soap is used in hard water. (b) Write the ionic equation for the reaction that occurs when sodium carbonate is used to remove hardness in water.
  0m 54s

• 53.    A sample of a river water is suspected to contain zinc and sulphate ions. Describe how the presence of zinc ions and sulphate ions can be established.
  0m 47s

• 54.    Study the information in the table below and answer the questions that follow. A mixture containing 35g of #CuSO_4# and 78g of #Pb(NO_3)_2# in 100g of water at #60^0C# was cooled to #40^0C#. (a) Which salt crystallized out? Give a reason. (b) Calculate the mass of salt that crystallised out.
  1m 5s

• 55.    (a) Name two cations that are present in hard (b) Explain how the ion exchange resin softens hard water.water.
  0m 33s

• 56.    The flow chart below shows a sequence of reactions involving a mixture of two salts, mixture M. study it and answer the questions that follow. (a)Write a formular of the following: (i)anion in solid Q. (ii)the two salts present in mixture M. (b) write the ionic equation for the reaction in step (VI). (c) state and explain the observations made in step (V)
  3m 51s

• 57.    Aqueous hydrogen chloride reacts with potassium manganite (VII) to produce chlorine gas, while a solution of hydrogen chloride in methylbenzene has no effect on potassium manganite (VII).Explain this observation.
  0m 31s

• 58.    The table below gives the solubilities of substances T and U at #10^oC# and #40^oC# When aqueous mixture containing 55g of T and 12g of U at #80^oC# was cooled to #10^oC#, crystals formed. (a) Identify the crystals formed. (b) Determine the mass of the crystals formed. (c) Name the method used to obtain the crystals.
  1m 21s

• 59.    Starting with zinc sulphate solution, describe how sample of zinc oxide can be obtained.
  0m 42s

• 60.    (a) Naturally occurring magnesium consists of three isotopes. 78.6% #\ ^24Mg#;10% #\ ^25Mg# and #\ ^26Mg#.Calculate to one decimal place, the relative atomic mass of magnesium. (b) Wen magnesium burns in air, it forms a white solid and grey- green solid. When a few drops of water re added to the mixture, a gas that turns red litmus paper blue is evolved. Identify the: (i) White solid
  2m 44s

• 61.    A compound whose general formula is #M(OH)_3# reacts as sown by the equation below. (a) What name is given to compounds which behave like #M(OH)_3# in the two reactions. (b) Name two elements whose hydroxides behave like that of M.
  0m 36s

• 62.    W is a colourles aqueous solution with the following properties: I it turns blue litmus paper red. II On addition of cleansed magnesium ribbon, it gives off a gas that burns with a pop sound. III On addition of powdered sodium carbonate, it gives off a gas which forms a white precipitate with calcium hydroxide solution. IV When warmed with copper (II) oxide powder, a blue solution is obtained but
  2m 46s

• 63.    (a) Define a soluble base. (b) Aqueous solutions of 2M ethanoic acid and 2M nitric(V) acid were tested for electrical conductivity. Which solution is a better conductor of electricity? Explain.
  0m 43s

• 64.    Explain why a solution of sodium chloride conducts electricity while that of sugar does not.
  0m 21s

• 65.    (a) Complete the following table. (b) Explain why a solution of ammonia in methylbenzene has no effects on red litmus paper while in aqueous ammonia red litmus paper turns blue.
  1m 27s

• 66.    Chemical tests were carried out on separate samples of water drawn from the same source. The observations made were recorded as shown in Table 4. State the inferences made in reactions: (i)........................... (ii)............................. (iii)..............................
  2m 14s