find the ratio by mass of the combining elements in the following compounds: (i). Al2(so3) (ii). CaCl2
Answers
In a reaction 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass carbonate.
Ans.
Sodium carbonate + Ethanoic acid → Sodium ethanoate + Carbon dioxide + Water
5.3 g + 6 g → 8.2 g + 2.2 g + 0.9 g
LHS RHS 11.3 g = 11.3 g (Mass of reactant) (Mass of product) This shows, that during a chemical reaction mass of reactact = mass of product.
2. Hydrogen and oxygen combine in the ratio of 1 : 8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Ans. Ratio of H : O by mass in water is: Hydrogen : Oxygen → H2O 1 : 8 = 3 : x x = 8 × 3 ∴ 24 g of oxygen gas would be required to react completely with 3 g of hydrogen gas.
3. Which postulate of Dalton's atomic theory the result of the law of conservation of mass?
Ans. The postulate of Dalton's atomic theory that is the result of the law of conservation of mass is-the relative number and kinds of atoms are constant in a given compound. Atoms cannot be created nor destroyed in a chemical reaction.
4. Which postulate of Dalton's atomic theory can explain the law of definite proportions?
Ans. The relative number and kinds of atoms are constant in a given compound.