. When 5g of Calcium is burnt in 2g of Oxygen
then 7g of calcium oxide is produced. What
mass of calcium oxide will be produced when
5g of calcium reacts with 20 g of oxygen?
Answers
When 5g of calcium is burnt in 2g of oxygen ,we get 7g of calcium oxide From this we understand that, calcium and oxygen combine in the ratio 5:2. Hence when 5g of calcium is burnt in 20g of oxygen,it will produce only 7g of calcium oxide. This is in accordance with law of constant proportions.
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Answer:
When Calcium is burnt in Oxygen the following reaction takes place.
2Ca + O₂ → 2CaO
Answer(a). From the reaction it is clear that 2 moles of calcium reacts with 1 mole of oxygen to give 2 moles of CaO. So the mole ratio is 2:1:2.
Now it is given that 5 g of Ca reacts with 2 g of oxygen to give 7 g of CaO.
N.O of moles of Ca = 5/40 = .125
N.O of moles of O₂ = 2/32 = .0625
here O₂ is limiting reactant and will disappear first and since 1 mole of O₂ forms 2 moles of CaO ,therefore .0625 moles of O₂ will form .125 moles of CaO and it is given tha 7 g of Cao is formed.
In the second case 20 g of O₂ i.e .625 moles of O₂ is used and hence Ca is the limiting reactant which is present 5g i.e .125 moles and as it's given that 2 moles of Ca forms 2 moles of CaO ,therefore 0.125 moles of Ca will form 0.125 moles of CaO.
So mass of CaO produced = 0.125*56 = 7g
The law of Chemical combination that governs this is "Law of Conservation of Mass". According to this law mass of product in a chemical reaction is equal to the mass of reactants.
Answer(b). Chemical Formula of Calcium Oxide is CaO.
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