CHM 191 TMA SOLUTIONS

CHM191 TMA Question and answer

Q1 In redox titration involving potassium permanganate, if the contents of the conical flask turn brown, it means _____was added...

 Insufficient acid catalyst
 Insufficient base catalyst
 Insufficient catalyst
 all of the above

Q2 Potassium permanganate is a self-indicating reagent because of its different characteristic _______ in either the acidic or basic medium
 Colour change
 Colour stability
 solubility
 oxidation state

Q3 Potassium permanganate can be used to estimate the ________of a substance
 Valency
 water of hydration
 reactivity
 percentage purity

Q4 IO$${_3}{^2-}$$ + SO$${_3}{^2+}$$ ­­→ I +SO$${_4}{^2-}$$ The oxidation state of oxygen in the product’s equation is______
 +3
 +6
 -3
 +6

Q5 IO$${_3}{^2-}$$ + SO{_3}{^2}$$+ the oxidation state of oxygen in the equation is ______
 -2
 -4
 +4
 +2

Q6 A substance which loses water of hydration upon exposure to atmosphere is called?
 Deliquescent substance
 Efflorescence substance
 Anhydrous substance
 Hygroscopic substance

Q7 Volumetric analysis involving iodine are usually referred to as___________
 iodotitration
 iodine acid titration
 halogenmetry
 iodometry

Q8 In the _____, standard solutions of iodine are used to estimate directly the concentrations of some oxidizable species.
 Direct method
 indirect method
 standard method
 calibrated method

Q9 Of all the oxidizable species available for use, iodine titration are usually used with the___
 sulphate ions
 Thiopsulphate
 hydrogensulphate
 thioesters

Q10 The colour changes accompanying the varying change in oxidation states of iodine and its ion can be used to indicate the________
 Iodine complxity
 iniyial point
 end point
 all of the above

Q11 The most commonly used external indicator for iodine titration is_________
 Glucose solution
 hydrogen chloride
 Protein solution
 starch solution

Q12 The starch solution forms a _______complex with the tri-iodide ion during the titration that is rapidly discharge at the end point
 Light blue
 Blue
 Blue black
 Brick red

Q13 Thus using starch as indicator, the colour variations of the solution depend on ______formation of the starch with iodide ion formed in the last stage of the titration.
 Complex
 Coloid
 Hydrolysed
 non of the above

Q14 For this reason and in order to avoid complications in the end point detection, the starch indicator is added at the______ colouration of the solution which is near the end point
 Yellow
 Light yellow
 Colourless
 Dark yellow

Q15 Complete the colour change in iodometry analysis. _______(initially)→
 Red-orange
 Dark-brown
 Brown
 Red-brown

Q16 Light yellow colouration is observed at near end point of the iodometry analysis. True or false___
 True
 False
 Partially true
 Indifferent

Q17 During iodometry analysis the blue black colouration appear at the end of the titration. True or false_____
 True
 False
 Partially true
 Indifferent

Q18 The oxidation potentials of Na is________
 11
 23
 271
 2.71

Q19 The study of thermal changes in chemical and physical processes is known as________
 thermochemistry
 Thermodynamics
 A and B
 B only

Q20 The _________is the amount of heat released or observed for a given amount of reactants or products
 heat of reaction
 heat of combustion
 heat of neutralization
 heat of formation

Q21 Predict the colour of methyl orange when $$p{^H}$$ is 8?
 Pink
 Orange
 Yellow
 Blue

Q22 At complete neutralization point, the litmus paper colour turns?
 Yellow
 Red
 Blue
 Purple

Q23 At neutralization point the $$P{^H}$$ value is?
 seven
 zero
 fourteen
 one

Q24 What is a $$P{^H}$$ of a solution?
 It is the measure of base concentration in the solution
 It is the measure of hydrogen ions concentration in the solution
 It is the measure of acid concentration in the solution
 It is the measure of hydroxyl ions concentration in the solution

Q25 In an acid base titration conducted by a student the colour of the solution in the beaker changed from colourless to pink when phenolphthalein was used as an indicator, what went wrong?
 The base was stronger than the acid
 The acid base ions are at equilibrium
 The beaker was occupied by acid solution instead of base.
 The titration time was overdue

Q26 Which of the following options is an indicator use for acid-base titration?
 Methylbenzene
 Bromohexane
 phenol
 Methyl orange

Q27 The point at which stoicheometrically equivalent quantities of substance have been brought together is known as?
 Equivalence point of titration
 Saturated point of titration
 End point of titration
 Neutralization point of titration

Q28 The concentration of pure HCl 11.7 Molar if $$20 cm{^3}$$ of the acid is diluted to $$250 cm{^3}$$ to give concentration of $$0.936 mol.dm{^3}$$ substitute this values on this equation; CIVI=C2V2?
 12.636 X 270 = C1 X 20
 11.7 X 20 = 0.936 X 250
 0.936 X 250 = 11.7 X 20
 11.7 X 250 = 0.936 X 20

Q29 Give reason why water should not be added to acid during carrying out acid-base titration?
 The procedure can cause explosion
 The acid is hygroscopic and will cause explosion when added to water
 The dissolution of acid in water is exothermic which may cause explosion
 The acid is corrosive and can destroy the glass ware

Q30 A table of requirement for laboratory experiment contains the following except?
 Quantity of apparatus
 List of apparatus
 List of chemicals
 List of weight of each reagents

Q31 A substance which takes in only moisture upon exposure to atmosphere is refer to as?
 Deliquescence substance
 Anhydrous substance
 Efflorescence substance
 Hygroscopic substance

Q32 A substance which loses water of hydration upon exposure to atmosphere is called?
 Deliquescent substance
 Efflorescence substance
 Anhydrous substance
 Hygroscopic substance

Q33 If 2 cm3 of a stoke solution contains 1 mole of an acid how would you prepare 1 molar concentration of that acid in 250 cm3 of water?
 Dissolve $$2 cm{^3}$$ of the stoke solution in 250 cm3 of water
 Dissolve $$1 cm{^3}$$ of the stoke solution in $$250 cm{^3}$$ of water
 Dissolve $$2 cm{^3}$$ of the stoke solution in $$248 cm{^3}$$ of water
 Dissolve $$1 cm{^3}$$ of the stoke solution in $$249 cm{^3}$$ of water

Q34 In a chemistry laboratory a stoke bottle of acid solution reads, “1.25 specific gravity”; what does that mean?
 It means $$100 cm{^3}$$ of that solution weight 12500 g
 It means $$1 cm{^3}$$ of that solution weight 1250 g
 It means $$1 cm{^3}$$ of the weight 125 g
 $$1 cm{^3}$$ of that solution weight 1.25 g

Q35 A solution contains 1.2 Molar concentration, what volume of it must be diluted with water to give 600 mls of 0.5 Molar solution?
 25 mls
 300 mls
 600 mls
 575 mls

Q36 In preparing a standard solution, two factors must be considered?
 1. The solute must be solid and 2. the solvent must be liquid
 1.The solute must be pure and 2. a suitable solvent be measured todefinite volume
 1.The solvent must be water and 2. the solute must be crystal form
 1.The solute’s nature must be known and 2. the solvent can be unknown

Q37 Define standard solution?
 A solution of which the concentration is partially known
 Concentration which has 1 mol dissolved in 1 dm3 of solvent
 A solution of which the concentration is accurately known
 A solution containing a pure substance dissolve in a known volume of solvent

Q38 What is the w/v percentage concentration of 300ml of NaCl(aq) containing 5 g NaCl?
 $$1.66 % w/v$$
 $$305 % w/v$$
 $$150 % w/v$$
 $$60 % w/v$$

Q39 Calculate the mass of NaCl in 450 g of NaCl solution containing NaCl w/w %?
 485 g
 450 g
 35 g
 157.5 g

Q40 What is the percentage w/w % ethanol if 5 g of ethanol is dissolved in 20 g of water?
 $$72 % w/w$$
 $$20 % w/w$$
 $$5 % w/w$$
 $$25 % w/w$$

Q41 One of the disadvantages of acid-base titration is?
 Large quantity of the sample(s) is required
 Takes longer time for reaction to start
 The acid need to be handled with care
 Requires careful attention to reach end point accurately

Q42 All are advantages of acid base titration except?
 Simple to do
 Less accuracy and precision
 Cost effective
 Do not need high expertise

Q43 The equation NaOH + HCl $$→$$NaCl + H2O is a ____?
 Acid base reaction
 Oxidation reaction
 Neutralization reaction
 Reduction reaction

Q44 When performing acid-base titration, one should first?
 Rinse the burette twice with acid solution
 Fill the burette twice with acid solution
 Fill the burette twice with base solution
 Rinse the burette twice with base solution

Q45 Which of these is a method of finding the equivalence point?
 PH indicator
 Amperometry
 Thermometric titrametry
 All of the above

Q46 What is a titrant in titration analysis?
 Unknown concentration and volume of an analyte
 Known concentration and volume of an analyte
 Partially unknown concentration and volume of acid
 Partially known concentration and volume of an analyte

Q47 What is a titrand in titration analysis?
 Known concentration of an analyte
 Partially known concentration of an analyte
 Partially unknown concentration of acid
 Unknown concentration of an analyte

Q48 During acid-base titration sulphuric acid would be dissociated into what ions?
 $$H{^+} + SO{_4}$$
 $$H{^-} + SO{_4}{^-}$$
 $$2H{^+} + SO{_4}{^-}$$
 $$H{_2} + SO{_4}$$

Q49 Both molarity and normality are measures of concentration. True or false?
 True
 Partially true
 false
 Indifferent

Q50 Choose the most suitable water for use in acid base titration?
 Distilled water
 Deionised water
 Temporary hard water
 Permanent hard water

Q51 A student used a hard tap water and performed and acid base titration. In few lines explain what would happen to his result?
 The starting solution would be more acidic as such it would consume more base to achieve the equivalence point
 the student cannot get an equivalence point owing to the fact that tap water was used not distilled water
 The solution would require more of indicator at the beginning of the experiment
 the starting solution would be more alkaline therefore it would require more volume of acid than expected

Q52 A 25 ml solution of 0.5 M NaOH is titrated until neutralized into a 50 ml sample of HCl?
 50 mol
 0.125 mol
 0.25 mol
 0.5 mol

Q53 What is the importance of back titration?
 To determine the concentration of a substance that is in excess after a chemical reaction.
 To determine the base in excess.
 To determine the acid in excess.
 To determine the average value of acid base titration.

Q54 What is the implication of adding a phenolphthalein as an indicator during the titration of HCl against Na2CO3?
 The end point will appear when only half of Na2CO3 has been used
 The end point will appear at the first drop of the acid.
 The end point will appear when half of the HCl has been used.
 The indicator will be sensitive to the acid alone

Q55 Which of these indicators will be suitable for use in titration involving a weak acid and a strong base?
 Any indicator
 Phenolphthalein
 Methyl orange
 No suitable indicator

Q56 What type of indicator will be suitable for use in a titration involving H2SO4 + NH3(ag)?
 Phenolphthalein
 Methyl orange
 Any indicator
 No suitable indicator

Q57 An example of a strong acid is?
 $$H{_2}SO{_3}$$
 $$CH{_3}COOH$$
 $$H{_2}C{_2}O{_4}$$
 $$H{_2}SO{_4}$$

Q58 What is a strong acid?
 Any acid that ionizes completely in solution
 Any acid which turns blue litmus paper red
 Any acid that is highly corrosive and can cause burn to the skin
 Any acid whose pH is less than 3

Q59 An indicator X was added to an acid solution in a beaker but no colour change was observed give the name of the indicator X?
 Methyl orange
 Bromothymol
 Phenolphthalein
 Litmus paper

Q60 What is the colour of bromothymol when added to an acid solution?
 Blue
 Red
 Yellow
 Colourless

Q61 The unit µg is equivalent to?
 $$10{^-3}$$ Kg
 $$10{^-6}$$ Kg
 $$10{^-12}$$ Kg
 $$10{^-9}$$ Kg

Q62 When filtration is carried out under reduced pressure is called?
 Pressure filtration
 Simple filtration
 Ordinary filtration
 Suction filtration

Q63 The unit of a volume express in $$dm{^3}$$ is equivalent to?
 1 litre or 100 ml
 $$10{^3}$$ cm or 1 litre
 100 $$cm{^3}$$ or 1 litre
 1000 ml or 10 litre

Q64 Define precipitation in respect to wet chemical analysis?
 A method of converting ions in solution into an insoluble compound
 The process of separating solid (crystals or precipitate) from the liquid (mother liquor)
 A method of reducing the volume of by heating
 A method of converting water vapour in to liquid water

Q65 What is a mole?
 The amount of substance which contains as many element as there are atoms in 12 g carbon 12
 The amount of substance which is contain in a solution
 The amount of substance equivalent to carbon 12 atom present in a solution
 All the options are correct

Q66 Why do we heat precipitates during gravimetric analysis?
 To obtain a compound of constant composition
 To increase the solubility of the precipitates
 To dry the precipitates
 To speed the reaction rate of the precipitates

Q67 The Avogadro number $$6.02 X 10{^23}$$ is equivalent to?
 Number of atoms, ions or molecules in a mole
 Number of mole of an atom equivalent to carbon atom
 Number of elementary units in a mole of a substance
 All options above are correct

Q68 Choose from the list of chemicals given and determine which has negative effect on skin?
 Tetraoxosulphate(VI)and hydrogensulphide
 Esters and ethanols
 Benzene and benzoylchloride
 Phenols and hydrogenfloride

Q69 Calculate the molar mass of 1 mole of a pure substance weighting X g?
 M=2X g $$mol{^-1}$$
 M=1/X g $$mol{^-1}$$
 M=X g $$mol{^-1}$$
 M=1 g $$mol{^-1}$$

Q70 Which of these hazardous chemicals are likely to cause dizziness and are carcinogenic?
 Ethanol
 benzene
 Silvernitrate
 Phenol

Q71 Calculate the mass of 0.5 moles of water?
 9.408 g
 18.016 g
 18.071 g
 4.504 g

Q72 The hazardous effect of chlorinated alkanes is?
 Highly oxidizing
 irritant
 Skin burns
 Causes mental confusion

Q73 Calculate the number of moles in 24 g of oxygen gas?
 281 mol
 265 mol
 7.8 mol
 3.8 mol

Q74 All are laboratory safety tips except?
 Wearing lab coat or apron
 Close all windows and doors
 Never work alone in the laboratory
 Be familiar with the position of some safety equipment

Q75 Calculate the molar mass of a pure substance if 2 moles of the substance has a mass of 35 g?
 17.5 $$g mol{^-1}$$
 70 g $$mol{^-1}$$
 35 g $$mol{^-1}$$
 37 g $$mol{^-1}$$

Q76 Qualitative analysis helps in determining what in a given solution?
 How long it will take for reactant to react to form products
 How much of a component is present in that solution
 The quantity of the solvent required to form solution with the component
 What type of component is present in that solution

Q77 Define molality of a solution?
 Weight in grams of a substance per formula weight in kilograms of that substance
 The number of moles of solute per $$dm{^3}$$ of a solution
 The number of moles of solute in one kilogram of solution
 Moles of solute per volume of solution express in litre

Q78 Quantitative methods help in determining what in a solution?
 How much of a component is present in the solution
 What type of component is present in a solution
 The quantity of a solvent required to form a solution with the component
 How long will take for reactant to react in order to form products

Q79 Normality can be defined as?
 Moles of solute in 1 $$dm{^3}$$ of solution
 Weight in gram of a substance per formula weight in kilo gram of substance
 Number of gram equivalent weight of a solute in one litre of solution
 All the options are correct

Q80 The various method of quantitative analysis include?
 Acid –base titration and Oxidative analysis
 Gravimetric, spectrophotometric and volumetric methods
 Titration, Gravimetric, and Volumetric
 Spectrophotometric, Oxidative and Neutralization methods