When 15 grams of wood burns completely in 25 grams of oxygen, 20 grams of water vapor and some carbon dioxide are given off. a. identify each of the reactant(s) and the product(s). b. how many grams of carbon dioxide would be produced in this example? c. what is the name of the law that you need to determine your answer for b?

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 " .