Answer :
The correct answer for A . Reactant = woods and oxygen ,
Products = water vapor + carbon dioxide
B. Mass of carbon dioxide = 20 g
C. Law of Conservation of Mass .
Given : Mass of wood = 15 g Mass of oxygen = 25 g
Mass of water Vapor = 20 g
A. To identify the reactant and products
Reactants : These are starting material of chemical reaction . They undergo chemical change by breaking bond and forms new bonds to form the products.
Products : These are substances which are formed in a chemical reaction when new bonds are formed .
In question following reaction take place :
Woods + Oxygen → Carbon dioxide + water vapor
Since woods are burning in presence of oxygen means bonds are breaking in them . Hence Woods and oxygen are REACTANTS
While Carbon dioxide and water vapor are produced in the reaction , they are known as PRODUCTS
B. To find mass of Carbon dioxide :
Mass of carbon dioxide can be calculated using Law of conservation of mass .
The law states "" Mass is neither destroyed nor created in an chemical reaction . Or Mass of elements before reaction is equal to mass of elements after the reaction . ""
Hence ., it can be said :
Sum of mass reactants = sum of mass of products
Mass of reactants = Mass of Woods + mass of oxygen = 15 g + 25 g = 40 g
Mass of reactant = mass of product = 40 g
Mass of products = mass of carbon dioxide + mass of water vapor
40 g = mass of Carbon dioxide + 20 g
Mass of Carbon dioxide = 20 g
C. To identify the law .
As already discussed in part B. the law is " Law of Conservation of Mass " .