1 ) Alkali metals form . . . . . . . . . . . . . , A ) covalent compounds , B ) ionic compounds , C ) both ,

1 ) Alkali metals form  . . . . . . . . . . . . . ,

A ) covalent compounds ,                                  B ) ionic compounds ,

C ) both ,                                                    D ) none of these ,

Correct Answer : -   B ) ionic compounds ,

2 ) Washing soda has formula : - Na2CO3 10.H2O .

3 ) Net charge on ferrous ion is ( + 2 ) and ferric ion is ( + 3 ) .

 

4 ) The total number of protons in 10 g of calcium carbonate is ? ( NA = 6.023 x 10 ^ 23 ) .

A ) 15 x 10 ^ 20 ,                                       B ) 30 x 10 ^ 23 , 

C ) 34 x 10 ^ 27 ,                                       D ) None of these ,

Correct Answer : -   B ) 30 x 10 ^ 23 , 

Solution : -

No. of protons in CaCO3 = 20 + 6 + 24 = 50 .

Total no. of protons = moles x ( no. of protons ) x NA .

Total no. of protons = ( 10 / 100 ) x 50 x ( 6.023 x 10 ^ 23 ) ,

Total no. of protons = 30 x 10 ^ 23 ,  Answer .

 

5 ) In Potassium super oxide ( KO2 ) , the oxidation state of O is : -   - 1 / 2 .

A ) 1 ,                                                         B ) - 1 / 2  ,

C ) 1 / 2 ,                                                    D ) None of these ,

Correct Answer : -   B ) - 1 / 2  ,

 

6 ) One mole of gas refers to the no. of molecules in 22.4 litres of a gas at STP .

 

7 ) Among the following pairs , the one which illustrate the law of multiple proportions is : -

A ) HCl , NH3 .                                           B ) H2S , SO2 .

C ) CuO , Cu2O .                                       D ) CS2 , FeSO4 .

Correct Answer : -   C ) CuO , Cu2O .

Explanation : -

In option A ) charges on H is  +1 , -3 .  So incorrect .

In option B ) charges on S is  -2 , +4 .  So incorrect .

In option C ) charges on Cu is  +2 , +2 .  So correct .

In option D ) charges on S is  -4 , +2 .  So incorrect .

 

8 ) The element necessary for normal “ leaf ” development is calcium .

 

9 ) Lime ( CaO ) is often used as dehydrating agent .

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