1.) There is no change in the total mass of the substances reacting...

 

1.) There is no change in the total mass of the substances reacting in a balanced chemical reaction.

 True

 False

 

2.) In a chemical reaction, no material is lost or gained as original substances are changed to new substances.

 True

 False

 

3.) Calculate the total mass of the reactants and the products for the following balanced chemical equation.

                     C _(s) + O_{2 (g)} ---> CO_{2 (g)}

_a._ g of reactants = _b._ g of products

a. =

b. =

 

4.) If a reaction resulted in making 25 grams of product, what must have been the mass of the reactants?

 

5.) If the total mass of reactants for a certain reaction was 33 grams, and all of the reactants were converted to products, what must be the total mass, in grams, of the products? 

1. True

2. True

3. O₂ = 2.668 g, C = 0.996 g, CO₂ = 3.664 g

4. 25 g

5. 33 g

Step-by-step explanation

1. Law of conservation of mass

The law of conservation of mass states that the total mass of substances taking part in a chemical reaction is conserved during the reaction. Mass is never lost or gained in chemical reactions. We say that mass is always conserved. In other words, the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning. This is because no atoms are created or destroyed during chemical reactions.

2. The chemical reaction produces a new substance with new and different physical and chemical properties. Matter is never destroyed or created in chemical reactions. The particles of one substance are rearranged to form a new substance.

3. For the balanced chemical equation shown below:

  C _(s) + O_{2 (g)} ---> CO_{2 (g)}

Given a mass of m grams of carbon:

• mass O₂ = moles(O₂) × molar mass(O₂)

(a) Calculate moles C = mass(C) ÷ molar mass(C)

moles(C) = m ÷ 12.01 

(b) Use the balanced chemical equation to determine the mole ratio O₂:C

moles(O₂) : moles(C)   is   1 : 1

(c) Use the mole ratio to calculate moles O₂

moles(O₂) = (1 ÷ 1) × moles(C)

substitute value for moles(C)

moles(O₂) = 1/1 × (m ÷ 12.01)

(d) Calculate mass of O₂

mass(O₂) = moles(O₂) × molar mass(O₂)

= [1/1× (m ÷ 12.01)] × [2 × 16.00]

= [1/1 × (m ÷ 12.01)] × [32.00]

mass of O₂ = 2.668 g      mass of C = mass of CO₂ - mass of O₂ = 0.996 g         mass of reactant = mass of O₂ + mass of C = 3.664 g

• mass CO₂ = moles(CO₂) × molar mass(CO₂)       

(a) Calculate moles C = mass(C) ÷ molar mass(C)

moles(C) = m ÷ 12.01

(b) Use the balanced equation to determine the mole ratio CO₂:C

moles(CO₂) : moles(C)   is   1:1  

(c) Use the mole ratio to calculate moles MgO

moles(CO₂) = 1 × moles(C)

substitute in the value for moles(C)

moles(CO₂) = 1 × (m ÷ 12.01)

(d) Calculate mass CO₂

mass(CO₂) = moles(CO₂) × molar mass(CO₂)

= [1 × (m ÷ 12.01)] × [12.01 + 2 x 16.00]

= [1 × m ÷ 12.01] × 44.01

mass of CO₂ = 3.664 g

4. the total mass of the products must be equal to the total mass of the reactants.

5. the total mass of the products must be equal to the total mass of the reactants.