One part per million (ppm) of hardness means how many parts of $CaCO_3$ equivalent hardness?

1 part $CaCO_3$ per $10^6$ parts of water

1 part $CaCO_3$ per $10^3$ parts of water

1 part $CaCO_3$ per $10^4$ parts of water

1 part $CaCO_3$ per $10^9$ parts of water

CHE124 Unit 1: Water and its Treatment - MCQ Practice | B. Tech. Biotechnology

1 $Temporary hardness in water is caused mainly by the presence of which of the following?$

Types of hardness Easy

A.

Chlorides of calcium and magnesium

B.

Sulphates of calcium and magnesium

C.

Bicarbonates of calcium and magnesium

D.

Nitrates of calcium and magnesium

2 $Permanent hardness of water is due to the presence of which salts?$

Types of hardness Easy

A.

Bicarbonates of calcium and magnesium

B.

Chlorides and sulphates of calcium and magnesium

C.

Hydroxides of calcium and magnesium

D.

Carbonates of sodium and potassium

3 $Temporary hardness can be removed by which of the following methods?$

Types of hardness Easy

A.

Cooling the water

B.

Boiling the water

C.

Adding common salt

D.

Filtration through sand

4 $Hardness of water is conventionally expressed in terms of the equivalent amount of which compound?$

Units of hardness of water Easy

A.

B.

C.

D.

5 $One part per million (ppm) of hardness means how many parts of equivalent hardness?$

Units of hardness of water Easy

A.

1 part per parts of water

B.

1 part per parts of water

C.

1 part per parts of water

D.

1 part per parts of water

6 $How many ppm are equal to 1 degree Clark of hardness?$

Units of hardness of water Easy

A.

14.3 ppm

B.

1 ppm

C.

10 ppm

D.

50 ppm

7 $Which indicator is commonly used in the EDTA method for determining hardness of water?$

Determination of hardness by EDTA method Easy

A.

Eriochrome Black-T

B.

Phenolphthalein

C.

Methyl orange

D.

Litmus

8 $In the EDTA titration, the colour change at the end point is from$

Determination of hardness by EDTA method Easy

A.

Yellow to orange

B.

Colourless to pink

C.

Wine red to blue

D.

Blue to wine red

9 $The EDTA titration for hardness is carried out at a pH of about$

Determination of hardness by EDTA method Easy

A.

2

B.

10

C.

7

D.

4

10 $EDTA reacts with and ions to form a$

Determination of hardness by EDTA method Easy

A.

Gas

B.

Precipitate

C.

Stable complex

D.

Weak acid

11 $Alkalinity of water is mainly due to the presence of which ions?$

Alkalinity of water and its significance Easy

A.

Calcium and magnesium ions

B.

Chloride and sulphate ions

C.

Sodium and potassium ions

D.

Hydroxide, carbonate and bicarbonate ions

12 $Which indicator is used to determine alkalinity due to hydroxide and carbonate (phenolphthalein alkalinity)?$

Alkalinity of water and its significance Easy

A.

Phenolphthalein

B.

Potassium chromate

C.

Starch

D.

Eriochrome Black-T

13 $Total alkalinity of water is determined by titration using which indicator?$

Alkalinity of water and its significance Easy

A.

Phenolphthalein

B.

Methyl orange

C.

Eriochrome Black-T

D.

Litmus paper

14 $Which of the following is a common problem caused by using hard water in boilers?$

Boiler feed water and its treatment Easy

A.

Softening of water

B.

Reduced corrosion

C.

Increased fuel efficiency

D.

Scale and sludge formation

15 $Caustic embrittlement in boilers is caused mainly by$

Boiler feed water and its treatment Easy

A.

Dissolved calcium chloride

B.

Excess silica

C.

Excess dissolved oxygen

D.

Excess sodium carbonate/hydroxide

16 $In the lime-soda process, lime () is used mainly to remove$

Softening methods and numerical problems based on these methods Easy

A.

Temporary hardness

B.

Dissolved oxygen

C.

Colour

D.

Turbidity only

17 $In the zeolite (permutit) softening process, hardness-causing ions are exchanged for which ion?$

Softening methods and numerical problems based on these methods Easy

A.

B.

C.

D.

18 $The exhausted zeolite bed is regenerated by passing a solution of$

Softening methods and numerical problems based on these methods Easy

A.

Sodium hydroxide

B.

Calcium chloride

C.

Dilute sulphuric acid

D.

Sodium chloride (brine)

19 $Which membrane process uses pressure to force water through a semipermeable membrane, removing dissolved salts?$

Membrane based treatment processes Easy

A.

Aeration

B.

Sedimentation

C.

Reverse osmosis

D.

Coagulation

20 $The main purpose of chlorination of water is to$

Water treatment by chlorination Easy

A.

Reduce alkalinity

B.

Improve taste only

C.

Remove hardness

D.

Kill disease-causing microorganisms

21 $A water sample retains its hardness even after prolonged boiling. Which salts are most likely responsible for this behaviour?$

Types of hardness Medium

A.

and

B.

and

C.

and

D.

and

22 $A water sample has a hardness of expressed as . What is its hardness in ppm?$

Units of hardness of water Medium

A.

B.

C.

D.

23 $The hardness of a water sample is Clarke degrees (Clark). Express this in ppm of (1 Clark grain per gallon).$

Units of hardness of water Medium

A.

B.

C.

D.

24 $In the EDTA method for hardness estimation, why is Eriochrome Black-T (EBT) used along with a buffer of pH 10?$

Determination of hardness by EDTA method Medium

A.

It reacts with EDTA to intensify the blue colour

B.

It precipitates before titration

C.

It forms a wine-red complex with at that pH giving a sharp end point

D.

It keeps metal ions as free ions in solution

25 $of a standard hard water containing per mL consumed of EDTA. If of a sample water consumed of the same EDTA, what is the total hardness of the sample?$

Determination of hardness by EDTA method Medium

A.

B.

C.

D.

26 $Which of the following masking or handling steps is correct while estimating permanent hardness by the EDTA method?$

Determination of hardness by EDTA method Medium

A.

The sample is acidified with HCl before adding EBT

B.

The sample is boiled and filtered to remove bicarbonates before titration

C.

The sample is treated with excess then titrated directly

D.

The sample is heated to to volatilize permanent hardness

27 $For a water sample, the phenolphthalein alkalinity and methyl orange (total) alkalinity satisfy . Which ion is solely responsible for the alkalinity?$

Alkalinity of water and its significance Medium

A.

and

B.

only

C.

only

D.

only

28 $A water sample gives phenolphthalein alkalinity and total alkalinity (as). What are the carbonate and bicarbonate alkalinities respectively?$

Alkalinity of water and its significance Medium

A.

and

B.

and

C.

and

D.

and

29 $Why is the determination of the type of alkalinity important in boiler water treatment?$

Alkalinity of water and its significance Medium

A.

It directly measures permanent hardness of the water

B.

It increases the dissolved oxygen content usefully

C.

It fixes the boiling point of the feed water

D.

Excess caustic (OH⁻) and carbonate alkalinity can cause caustic embrittlement and priming

30 $Formation of scale on the inner walls of a boiler is undesirable mainly because it:$

Boiler feed water and its treatment Medium

A.

Increases the heat transfer efficiency

B.

Softens the water automatically

C.

Lowers the boiling point of water

D.

Acts as a thermal insulator causing overheating and fuel wastage

31 $In the phosphate conditioning of boiler water, sodium phosphate is added to:$

Boiler feed water and its treatment Medium

A.

Convert scale-forming salts into a soft, non-adherent sludge

B.

Neutralize the alkalinity completely

C.

Increase the dissolved oxygen concentration

D.

Raise the hardness for better heat transfer

32 $Caustic embrittlement in boilers is best prevented by:$

Boiler feed water and its treatment Medium

A.

Adding excess sodium carbonate to the feed water

B.

Removing all dissolved gases only

C.

Increasing the operating pressure

D.

Using sodium phosphate/tannin and maintaining proper Na₂SO₄:NaOH ratio

33 $Calculate the amount of lime (74% pure) required to soften of water containing equivalent to (as the salt, molar mass). Lime requirement pure.$

Softening methods and numerical problems based on these methods Medium

A.

B.

C.

D.

34 $In the zeolite (permutit) process, exhausted zeolite is regenerated by treating it with:$

Softening methods and numerical problems based on these methods Medium

A.

Dilute

B.

solution only

C.

solution

D.

Lime and soda

35 $In the ion-exchange (demineralization) process, water is passed first through a cation exchanger and then an anion exchanger. The water leaving the cation exchanger is:$

Softening methods and numerical problems based on these methods Medium

A.

Neutral and soft

B.

Alkaline due to

C.

Acidic due to liberated

D.

Rich in ions

36 $A water sample contains and . Calculate the lime and soda requirements (as equivalents) respectively. (Molar masses:,)$

Softening methods and numerical problems based on these methods Medium

A.

Lime, Soda

B.

Lime, Soda

C.

Lime, Soda

D.

Lime, Soda

37 $In reverse osmosis, pure water is obtained when pressure applied to the saline side is:$

Membrane based treatment processes Medium

A.

Less than the osmotic pressure

B.

Greater than the osmotic pressure of the solution

C.

Equal to the osmotic pressure

D.

Zero

38 $Which membrane process is primarily driven by an applied electric potential rather than pressure?$

Membrane based treatment processes Medium

A.

Ultrafiltration

B.

Electrodialysis

C.

Reverse osmosis

D.

Nanofiltration

39 $The disinfecting action of chlorine in water is mainly due to the formation of:$

Water treatment by chlorination Medium

A.

Hydrochloric acid ()

B.

Calcium chloride ()

C.

Chlorine dioxide ()

D.

Hypochlorous acid ()

40 $According to common drinking water standards, the desirable/permissible upper limit of total dissolved solids (TDS) is about:$

Specifications for drinking water Medium

A.

B.

C.

D.

41 $A water sample contains of and of . What is the total hardness expressed in ppm of ? (Molar masses:,)$

Units of hardness of water Hard

A.

B.

C.

D.

42 $In the EDTA titration of a hard water sample, of EDTA was used. of standard hard water containing per mL required of the same EDTA. What is the total hardness of the sample?$

Determination of hardness by EDTA method Hard

A.

B.

C.

D.

43 $Why is the EDTA titration for total hardness carried out at using an ammonia buffer rather than at low pH?$

Determination of hardness by EDTA method Hard

A.

EDTA only dissolves in alkaline media below pH 7

B.

At low pH precipitates as hydroxide before titration

C.

At high pH the complexes are stable and EBT indicator functions correctly

D.

The buffer converts into for detection

44 $Calculate the lime (as pure) required to soften L of water containing and . (Molar masses:,,)$

Softening methods and numerical problems based on these methods Hard

A.

B.

C.

D.

45 $A water sample gives phenolphthalein alkalinity and total (methyl orange) alkalinity as . Which ionic species and amounts are present?$

Alkalinity of water and its significance Hard

A.

,

B.

absent,,

C.

,

D.

, absent

46 $For a water sample, exactly. What does this condition indicate about the alkalinity-causing species?$

Alkalinity of water and its significance Hard

A.

and coexist

B.

Only is present

C.

and coexist

D.

Only is present

47 $A sample contains,, and . Which combination correctly represents the temporary hardness contributors?$

Types of hardness Hard

A.

and

B.

and

C.

and

D.

and

48 $Which sequence correctly explains caustic embrittlement in high-pressure boilers?$

Boiler feed water and its treatment Hard

A.

deposits as hard scale reducing heat transfer

B.

decomposes forming soft sludge in the drum

C.

hydrolyzes to, which concentrates in crevices and causes intergranular cracking of stressed metal

D.

Dissolved oxidizes iron to scale that flakes off

49 $An exhausted zeolite bed of capacity such that it softened water until breakthrough. It is regenerated with . Which reaction correctly represents regeneration?$

Softening methods and numerical problems based on these methods Hard

A.

B.

C.

D.

50 $In the lime-soda process, calculate the soda ash () required to treat L of water having permanent hardness of (as). (Molar mass)$

Softening methods and numerical problems based on these methods Hard

A.

B.

C.

D.

51 $In reverse osmosis, what minimum applied pressure condition allows pure water to be forced through the semipermeable membrane against a saline feed?$

Membrane based treatment processes Hard

A.

Applied pressure must equal the vapor pressure of water

B.

Applied pressure must equal atmospheric pressure only

C.

Applied pressure must exceed the osmotic pressure of the feed solution

D.

Applied pressure must be below the osmotic pressure to prevent fouling

52 $Which statement correctly distinguishes electrodialysis from reverse osmosis?$

Membrane based treatment processes Hard

A.

Electrodialysis uses an electric field to move ions through ion-selective membranes, whereas RO uses pressure to move water

B.

Both use pressure gradients but electrodialysis rejects only cations

C.

RO uses an electric field and electrodialysis uses pressure

D.

Electrodialysis removes water molecules while RO removes only gases

53 $During break-point chlorination, the residual chlorine curve dips before rising again. What chemistry occurs at the break point?$

Water treatment by chlorination Hard

A.

decomposes to release giving turbidity

B.

All chlorine is consumed and disinfection stops permanently

C.

Chloramines and reducing impurities are fully oxidized, after which free residual chlorine appears

D.

Chlorine reacts with forming bleaching powder

54 $Why does chlorination become less effective as water pH rises above about 8?$

Water treatment by chlorination Hard

A.

Chlorine gas becomes insoluble above pH 8

B.

converts to gas and escapes

C.

The equilibrium shifts toward, which is a weaker disinfectant than

D.

Bacteria develop alkaline resistance above pH 8

55 $Sodium aluminate () is sometimes added in internal boiler treatment. What is its primary function?$

Boiler feed water and its treatment Hard

A.

It precipitates as a hard adherent scale

B.

It releases oxygen scavenging free

C.

It raises acidity to neutralize

D.

It hydrolyzes to which flocculates finely suspended and colloidal matter into removable sludge

56 $In the demineralization (ion-exchange) process, water passed through a cation exchanger emerges acidic. What is the correct reason?$

Softening methods and numerical problems based on these methods Hard

A.

ions from resin hydrolyze to form acid

B.

Cations are replaced by from the resin, generating mineral acids in the effluent

C.

The resin releases lowering pH

D.

Anions are replaced by liberating bases

57 $A hardness of as is equivalent to how many degrees Clark (°Clark), given °Clark grain per gallon (imperial) and grain/gallon ?$

Units of hardness of water Hard

A.

B.

C.

D.

58 $According to WHO/BIS guidelines, which set of parameters for potable water is correct?$

Specifications for drinking water Hard

A.

Turbidity, pH -, TDS

B.

Turbidity, pH -, TDS (desirable)

C.

Turbidity, pH -, TDS

D.

Turbidity, pH -, TDS

59 $In EDTA determination of permanent hardness, a portion of the water is first boiled, filtered, then titrated. What does the boiled-sample titration measure?$

Determination of hardness by EDTA method Hard

A.

Alkalinity due to ions

B.

Permanent (non-carbonate) hardness, since carbonate hardness precipitates on boiling

C.

Only temporary hardness remaining in solution

D.

Total hardness including carbonate salts

60 $Priming and foaming in boilers both cause carry-over of water with steam. Which pairing correctly gives their principal causes?$

Boiler feed water and its treatment Hard

A.

Priming: dissolved oxygen corrosion; Foaming: hard scale on tubes

B.

Priming: caustic embrittlement; Foaming: scale

C.

Priming: high water level and sudden boiling; Foaming: dissolved oils/alkalis stabilizing bubbles

D.

Priming: excess; Foaming: low water level

Unit 1: Water and its Treatment - Practice Quiz

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