# Chhattisgarh State Class 9 Science Chapter 9 Solution

Chhattisgarh State Board Class 9 Science Chapter 9 Chemical Formula and Mole Concept Exercise Multiple Choice, Fill in the Blanks, Questions and Answers here.

## Chhattisgarh State Class 9 Science Chapter 9 Solution

1) Choose the correct option–

(i) The molecular weight of CH3OH is–

(a) 32 u (b) 29 u

(c) 25 u (d) 20 u.

Ans: – option (a) 32 u.

(a) Positively charged ion (b) negatively charged ion

(c) neutral atom (d) none of the above.

Ans: – option (a) positively charged ion.

(iii) Ions that have a negative charge are–

(a) Positively charged ion (b) Basic radicals

(c) Acidic radicals (d) Neutral atoms.

Ans: – option (a) acidic radicals.

(iv) The value of Avogadro’s number is–

(a) 6.022 × 1023 (b) 6.022 × 1022

(c) 6.022 × 1024 (d) 60.22 × 1023.

Ans: – option (a).

(v) The volume of any gas at 0oC and 1 atm pressure–

(a) 11.2 litre (b) 22.4 litre

(c) 100 litre (d) 33.8 litre.

Ans: – option (b) 22.4 litre.

2) Fill in the blanks

(i) Unit formula mass is used for ……… atomic mass……………………………….. compounds.

(ii) The molecular weight of C12H22O11 is ……….342 g/mol………………

(iii) The number of elements in (PO4)3-

…………..2……………………

(iv) The number of atoms in one mole of carbon is …….6.023×10^23…………..

(v) The mass of one mole of water is …………18g…………………

3) How do we get acidic and basic radicals?

Ans: – As we all know that positively charged compounds are known as the basic radicals and the positively charge hydrogen ion (H+) are present. In a negatively charged radicals are hydroxide ion or OH- are present.

4) What are polyatomic ions? Give examples.

Ans: – If any ion isconsisted of more than one atom then this element is known as the polyatomic ions. There is various example of polyatomic ion like hydroxide ion (OH-), nitrate ion.

5) Connect the appropriate pairs:

Column A.                                             Column B

(i) Number of atoms in one mole.    (i) 14 grams

(iv) The weight of one mole of (iv) 2 mol.

Nitrogen ion.

(v) The number of moles in 88 g of CO2.  (v) 6.022 × 1023.

Ans: –

 Column A Column B i)No of atoms in one mol. v)6.023×10^23 ii) Acidic radicals. Iii) SO4 2- iii) Basic radical ii)Mg2+ iv)The weight of one mole of nitrogen. i)14 gram v)The no of moles in 88g of CO2. iv)mole.

5) What is unit formula mass? Calculate the unit formula mass of MgSO4.

Ans: – The unit mass formula is the method of calculating the atomic mass. The mass of the MgSO4 is 120 gm. (24.31 + 32 + 64).

6) If the formula of the carbonate of a metal is M2CO3then what will be the formula of its nitrate.

Ans: – The formula of the nitrate of the metal will be M(NO4).

7) If the formula of aluminium sulphate is Al2(SO4)3 then what is the charge on Al ion and what is theformula of zinc sulphate?

Ans: – The charge on Al is +3 for the compound aluminium sulphate Al2(SO4)3.

The formula of zinc sulphate ZnSO4.

8) The ion X has two positive charges on it. Write the formulae of the nitrate, sulphate and phosphateof X.

Ans: – The formula of nitrate is X3(NO4)2. The sulphate is XSO4 and the phosphate is X3(PO4)2.

9) Calculate the molecular weights of the following:

PCl5, H2O2, S8, HCl, NH3.

Ans: – The molecular weight is –

PCl5: – 15×2 + 35.5×5= 208. H2O2: – 1×2 + 16×2= 34; S8= 32×8=256; HCl: – 1 + 35.5= 36.5; NH3: – 14 + 1×3= 17;

10) Calculate the masses of the following-5 moles of ammonia, 0.5 moles of water, 1.50 moles of Na+ ions, 0.2 moles of oxygen atoms.

Ans: – The masses of 5 mole ammonia (m.w =17) = 5×17=85.

The masses of 0.5 moles of water (m. w=18) = 0.5×18=9;

The masses of 1.5 moles of Na (m. w=23) = 1.5×23=34.5.

The masses of 0.2 moles of oxygen (m. w=16) = 0.2×16= 8.

11) Calculate the number of moles in the following:

12 g of O2, 22 g of CO2.

Ans: – The 32g of O2 is 1 mole, then 12g of O2 is (32/12=2.66) 2.66 moles.

The 44g of CO2 is 1 mole, then 22g of CO2 is 0.5 mole.

12) Determine the chemical formulae of the following using the crisscross method: Iron sulphate, Copper nitrate, Sodium sulphide, Magnesium hydrogen carbonate.

Updated: January 6, 2022 — 2:56 pm