Q57. What is Avogadro Constant or Avogadro Number?

Or

What is the relationship between a mole and Avogadro’s Number?

 

Q58. What is an ion? Explain with the help of example.

 

Q59. A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.

 

Q60. A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold?

 

Q61. Express each of the following in kilograms

(a) 5.84×10-3 mg

(b) 58.34 g

(c) 0.584g

(d) 5.873×10-21g

 

Q62. The difference in the mass of 100 moles each of sodium atoms and sodium ions is 5.48002 g. Compute the mass of an electron.

 

Q63. Write the molecular formulae for the following compounds

(a) Copper (II) bromide

(b) Aluminium (III) nitrate

(c) Calcium (II) phosphate

(d) Iron (III) sulphide

(e) Mercury (II) chloride

(f) Magnesium (II) acetate

 

Q64. Give the formulae of the compounds formed from the following sets of elements

(a) Calcium and fluorine

(b) Hydrogen and sulphur

(c) Nitrogen and hydrogen

(d) Carbon and chlorine

(e) Sodium and oxygen

(f) Carbon and oxygen

 

Q65. (a) In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called ————.

(b) A group of atoms carrying a fixed charge on them is called ————.

(c) The formula unit mass of Ca3 (PO4)2 is ————.

(d) Formula of sodium carbonate is ———— and that of ammonium sulphate is ————.

 

Q66. Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them. (You may use appendix-III).

(a) Ammonia

(b) Carbon monoxide

(c) Hydrogen chloride

(d) Aluminium fluoride

(e) Magnesium sulphide

 

Q67. Calculate the number of molecules of sulphur (S8) present in 16 g of solid sulphur.

 

Q68. Which of the following correctly represents 360 g of water?

(i) 2 moles of H20

(ii) 20 moles of water

(iii) 6.022 × 1023 molecules of water

(iv) 1.2044×1025 molecules of water

(a) (i) (b) (i) and (iv)

(c) (ii) and (iii) (d) (ii) and (iv) 

 

Q69. What is the mass of:

(a) 0.2 mole of oxygen atoms?

(b) 0.5 mole of water molecules?

 

Q70. What is the mass of—

(a) 1 mole of nitrogen atoms?

(b) 4 moles of aluminium atoms (Atomic mass of aluminium = 27)?

(c) 10 moles of sodium sulphite (Na2SO3)?

 

Last modified: Tuesday, 25 May 2021, 6:54 PM