Conservation of Mass
Name ___________________
Practice Sheet
Period _____
1) Which of the following statements best defines the law of conservation of mass?
A. Mass cannot be created but it can be destroyed under extreme pressure.
B. Mass cannot be conserved during a chemical reaction; a little bit of mass is always lost.
C. The mass of a closed system cannot change over time; mass cannot be created nor
destroyed.
D. When added to a system, energy can destroy mass.
2) In a chemical reaction, 300 grams of reactant A are combined with 100 grams of
reactant B. Both A and B react to completion. How much will the product(s) weigh?
A. 200g
B. 400g
C. 300g
D. Cannot be determined
3) In a reaction, 25 grams of reactant AB breaks down into 10 grams of product A and an
unknown amount of product B. Using the law of conservation of mass, how much
does product B weigh?
A. 25g
4)
B. 10g
REACTANT(S)
C. 15g
D. Cannot be determined
PRODUCT(S)
Magnesium + Oxygen ------> Magnesium Oxide
48.6 g
+ 32.0 g ----->
80.6 g (1)
a. What is the mass of each reactant?
b. What is the mass of the product?
c. What is the total mass of reactants?
d. Does this experimental data support the Law of Conservation of Mass? Explain.
Answer questions 1—4 for each reaction below.
1) How many atoms of each element are there in the reactants?
2) How many atoms of each element are there in the products?
3) Does this equation support the Law of Conservation of Matter?
4) If yes, explain why. If not, what needs to happen (could be one or both sides) to work?
H2 + O2
H2O
Al2O3
Al + O2
KClO3
KCl + O2
S8 + 02
H2 + N2
SO2
NH3