Name _________________________________________ Date ______________ Period __________
Conservation of Mass Worksheet
Round off ALL mass values to the nearest whole number.
1.) When 2 grams of Hydrogen (H2) react with 32 grams of Oxygen (O2) the reaction yields hydrogen peroxide
(H2O2). How many grams of H2O2 are produced in the reaction?____________
2.) What is the mass of one atom of Calcium (element 20) __________? What is the mass of one atom of Sulfur
(element 16) ____________? If one atom of Calcium reacts with one atom of Sulfur what is the mass of the
product (CaS) that is made? __________________.
3.) Refer to question #2 for help. If 40 grams of Calcium are reacted with 32 grams of sulfur how many grams
of Calcium Sulfide (CaS) are produced? ______________.
4.) What is the mass of two Hydrogen atoms (element 1) ___________? What is the mass of two Fluorine
atoms (element 9) ___________. Two atoms of Hydrogen react with two atoms of Fluorine to produce two
molecules of HF (hydrofluoric acid)? What is the mass of ONE molecule of HF?__________ What is the mass of
TWO molecules of HF? _____________ Which is the correct equation that shows the conservation of mass:
H2
+
F2  HF
OR
H2
+ F2  2HF
5.) Refer to question number 4 for help. One atom of Hydrogen has a mass of 1. Two atoms of Hydrogen will
have a mass of 2. A molecule of Hydrogen is written as H2. What is the mass of this molecule? ____________
A molecule of Fluorine is written as F2 because there are two atoms of Fluorine bonded together. What is the
mass of these two Fluorine atoms when they are combined __________?
Refer to the numbers above to solve the following problem. 2 grams of Hydrogen react with 38 grams of
Fluorine to make HF (Hydrofluoric Acid). If the mass of HF is 20 (H = 1 and F = 19) how many HF molecules must
you produce from the reaction between Hydrogen and Fluorine? ___________________
H2 + F2  2 HF (you must have the same number of atoms on both sides of the equation)
HINT:
Do the following chemical equations represent the Law of Conservation of Matter? Do you have the same
number of atoms on both sides of the equation?
7.) H2
+
O2  H2O
yes / no
explain ___________________________________________
___________________________________________________________________________________________
8.) 2Na + Cl2  2 NaCl
yes / no
explain ___________________________________________
_________________________________________________________________________________________
9.) Ca +
O2  CaO
yes / no
explain ___________________________________________
__________________________________________________________________________________________
10.) Hg2 + O2  2HgO
yes / no
explain ____________________________________________
___________________________________________________________________________________________