Question

1.The mass of copper oxide obtained by reacting 2.16 g of metallic copper with nitric acid followed by strond heating was found to give 2.7 g .In another experiment 1.15 g of copper oxide on reduction gave 0.92 g of copper. Show that the data illustrares the law of constant proportions. 2. What mass of silver nitrate will react with 6.5 g of sodium chloride to form 12.6 g of silver chloride and 8.4 g of sodium nitate. 3. If 6.3 g of sodium bicarbonate are added to 15 g of acetic acid, the residue left is found to weigh 18 g. What mass of carbon dioxide is released in the reaction. 4.0.24 g of a sample having Boron and oxygen was found on analysis to contain 0.96 g of Boron and 0.144 g of oxygen. Calculate the percentage composition of boron and oxygen present in the compound. 5. Write the molecular formulae of all the compound which can beframed from the followingions: (i)Al 3+ (ii)Na + (iii)Fe 2+ (iv)Cl - (v)SO4 2- (vi)No3 -

Answer 1

Mass of oxygen in the experiment is around 0.54g.

It is obtained by subtracting the mass of copper from copper oxide

Portion of the copper oxide in the experiment =2.16/2.7 *100%

= 80%

Percentage of oxygen in the experiment = 20%

Mass of copper in the copper oxide =1.15-0.23

=0.92g

Copper in Copper oxide =0/92/1/15*100%

=80%

We observe that ratio of mass of copper and oxygen are the same, therefore; it explains the proportion by mass.