1 ) An aqueous solution of sodium carbonate is alkaline because sodium carbonate is a salt of : -

1 ) An aqueous solution of sodium carbonate is alkaline because sodium carbonate is a salt of : - weak acid and strong base .

 

2 ) Epsom salt is magnesium sulphate .

 

3 ) Cement contains gypsum 2 % .

 

4 ) Generally metals from oxides are . . . . . . . . . . . ,

A ) acidic ,                                                                  B ) basic ,

C ) neutral ,                                                   D ) none of these ,

Correct Answer : -   B ) basic ,

 

5 ) The strongest bronsted base is : -

A ) ClO^- ,                                                                    B ) ClO^-₂ ,

C ) ClO^-₃ ,                                                                  D ) ClO^-₄ ,

Correct Answer : -   A ) ClO^- ,

Explanation : -

The strongest base is the substance that can accept H⁺ .

Oxidation state of central atom increases , so acidity increase .

Thus the order of acidic strength of conjugate acid would be : -

HClO < HClO₂ < HClO₃ < HClO₄ .

As we know that weaker the conjugate acid , stronger the conjugate base .

So , conjugate in order : -

HClO > HClO₂ > HClO₃ > HClO₄ .

 

6 ) The pH value of  M / 1000  solution of KOH and water is : -

A ) 9 ,                                                              B ) 10 ,

C ) 11 ,                                                                       D ) None of these ,

Correct Answer : -   C ) 11 ,

Solution  : -

So ,  KOH = M / 1000  =  10^(-3) M  .

So ,  KOH  ------------>  OH^-  +  K⁺  .

∴   OH^-  is strong base .

So  [OH^-] = 10^(-3)  ,

pOH  =  - log[OH^-]  =  - log [ 10^(-3) ] .

pOH  =  - (-3) log[ 10 ]  = 3 ( 1 )  = 3 .       ∴  log[ 10 ]  =  1 .

So ,

pH + pOH = 14 ,

pH  =  14 – pOH ,

pH = 14 – 3 = 11  ,  Answer

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