Tag: evs

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Questions Related to evs

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

$ RH _{2} $ (ion exchange resin ) can replace $ Ca^{2+} $ in hard water as : 
$ RH _{2}+Ca^{2+}\rightarrow RCa+2H^{+} $.


One litre of hard water after passing through $ RH _{2} $ has pH = 2. Hence, hardness in ppm of $ Ca^{2+} $ is:

  1. 200

  2. 100

  3. 50

  4. 125
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to the given reaction 


$ RH _{2}+Ca^{2+}\rightarrow RCa+2H^{+} $

Each mole $ Ca^{2+} $ ion replaced by 2 moles $ H^{+}$

1 mole $ H^{+} $ replaced $ \Rightarrow \dfrac{1}{2} = 0.5\,mole \,Ca^{2+} $

Given,
$ pH = 2 $

$ H^{+} = 10^{-2} = 0.01 $

0.01 mole $ H^{+} $ replaced $ = 0.01\times 05 = 0.005\,moles\,Ca^{2+} $

Mass $ Ca^{2+}$ replaced $ = 0.005\times 40 = 0.2\,g = 200\,mg $

Concentration or Hardness of $ Ca^{2+} = 200\,mg/L $

$ = 200\,ppm $   

Hence, the correct option is $\text{A}$

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

In a laboratory, hard water, required for an experiment, is not available. However, the following salts are available in the school laboratory :
1. Sodium sulphate
2. Calcium sulphate
3. Magnesium chloride
4. Sodium chloride
5. Calcium chloride
6. Potassium sulphate
Which of the above salts may be dissolved in water to obtain hard water for the experiment?

  1. 1,3 and 5

  2. 1,2 and 5

  3. 1,2,4 and 6

  4. 3 and 5 only

  5. 2,3 and 5
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The following salts may be dissolved in water to obtain hard water for the experiment
2. Calcium sulphate
3. Magnesium chloride
5. Calcium chloride

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Both temporary and permanent hardness in water is removed by:

  1. boiling

  2. filtration

  3. distillation

  4. decantation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Both temporary and permanent hardness in water is removed by distillation. Temporary hardness can be removed by boiling and filtration. Permenant hardnesscan be removed by: (1) adding washing soda, (2) permutit method (3) by using ion exchange resins.

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Both temporary and permanent hardness is removed on boiling water with :-

  1. $Ca(OH) _{2}$
  2. $Na _{2}CO _{3}$
  3. $CaCO _{3}$
  4. $CaO$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Temporary hardness is removed by boiling water with $NaOH$ and $Na _2CO _3$. $Ca(HCO _3 ) _2+2NaOH \rightarrow CaCO _3 \downarrow +Na _2CO _3+2H _2O$ Permanent hardness is removed by boiling water with sodium carbonate. $CaCl _2+Na _2CO _3 \rightarrow CaCO _3 \downarrow + 2 NaCl$

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks
Both temporary and permanent hardness in water is removed by________.

  1. boiling

  2. filtration

  3. distillation

  4. decantation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Both temporary and permanent hardness in water is removed by distillation. Temporary hardness can be removed by boiling and filtration. permanent hydration can be removed by adding washing soda, permutit method and by using ion exchange resins.
Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Temporary hardness of water can be removed by :

  1. boiling

  2. saponification

  3. clark's method

  4. chlorination
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

The temporary hardness of water can be removed by boiling. $Ca(HCO _3) _2 \xrightarrow {boil} CaCO _3 \downarrow + CO _2 \uparrow + H _2O$.

Clark's method which uses lime (calcium hydroxide), it is also used for removal of temporary hardness of water.
$Ca(HCO _3) _2+Ca(OH) _2 \rightarrow 2CaCO _3+2H _2O$.