Name: ______________________________
Date: _____________________
Homework: Law of Conservation of Mass
1. Which of the following will allow measurement of a solid’s mass with the greatest precision?
A 500 gram scale measuring in 1 gram increments
B 250 gram scale measuring in 0.5 gram increments
C 300 gram scale measuring in 0.1 gram increments
D 200 gram scale measuring in 0.2 gram increments
N2 + 3H2
2NH3
2. Which of the following statements accurately describes the reaction shown above?
A The mass of the hydrogen gas plus the nitrogen gas is less than the mass of the ammonia.
B The mass of the hydrogen gas is equal to the nitrogen gas plus the mass of the ammonia.
C The mass of the hydrogen gas minus the nitrogen gas is equal to the mass of the ammonia.
D The mass of the hydrogen gas plus the nitrogen gas is equal to the mass of the ammonia.
3. How many MOLES of each substance are present after the coefficient has been added:
2N2S4 = ___N + ___S
2MgCl2 = ___Mg + ___Cl
4CO = ___C + ___O
4CBr4 = ___C + ___Br
3KF = ___K + ___F
2CaCl2 = ___Ca + ___Cl
2AlBr3 = ___Al + ___Br
3MnO2 = ___Mn + ___O
3H2 =
SiS2 = ___Si + ___S
3BaCl2 = ___Ba + ___Cl
3H2O = ___H + ___O
___H
4. How many MOLES of each substance are present after the coefficient has been added:
2Mg(NO2)2 = ___Mg + ___NO2
3Pb(SO4)2 =
___Pb + ___SO4
2NH4Cl =
___ NH4 + ___Cl
2NaOH =
___Na + ___OH
3Na3PO4 =
___Na + ___PO4
2Al2(CO3)3 =
___Al + ___ CO3
3K2SO4 =
___ K + ___ SO4
3Ca(OH)2 =
___Ca + ___OH
5. Solve for each of the unknown masses below.
3g + ?g = 9.5g
3.1g + 8.2g = ?g
4g + ?g = 12.4g
8.2g + 17.3g = ?g
? = _____
? = _____
? = _____
? = _____
2g + ?g = 8.3g
5.1g + 3.8g = ?g
6.7g + ?g = 9.4g
18.3g + 9.2g = ?g
? = _____
?= _____
? = _____
? = _____
3.2g + ?g = 7.4g + 4.5g
? = _____
5.1g + 3.8g = ?g + 6.3g
? = _____
6.7g + ?g = 9.4g + 10.7g
? = _____
hydrogen
+
oxygen
water
8g
64 g
?g
1. 8 grams of hydrogen reacts with 64 grams of oxygen. Assuming all of the reactants are used
up, how much water will be produced?
A 72 g
B 56 g
C 64 g
D 144 g
S8
+
8O2
8SO2
2. If 64 g of sulfur react with 4 g of oxygen gas, what will be the mass of the sulfur dioxide
produced?
A 60 g
B 64 g
C 68 g
D 48 g
2Cu + O2  2CuO
3. When 63.5 g of copper reacts with 16.0 g of oxygen gas to form copper (II) oxide, no copper
or oxygen is left over. How much copper (II) oxide is produced?
A 3.97 g
B 47.5 g
C 79.5 g
D 143 g
mercury(II) oxide
oxygen
mercury
30.0 g
2.1 g
+
? g
4. According to the law of conservation of mass, how much mercury was present in the mercury
(II) oxide?
A 30 g
B 32.1 g
C 27.9 g
D 63 g
CaCl2 + Na2CO3  CaCO3 + NaCl
5. What coefficient values will balance the reaction shown above? (Show your work for each set
of coefficients.)
A 2, 1, 2, 1
B 1, 1, 1, 1
C 1, 1, 1, 2
D 1, 2, 1, 1
C6H12O6 + O2  CO2 + H2O
6. What coefficient values will balance the reaction shown above? (Show your work for each set
of coefficients.)
A 1, 6, 6, 6
B 2, 6, 6, 6
C 1, 3, 3, 3
D 2, 6, 3, 6
H2O + Li  LiOH + H2
7. What coefficient values will balance the reaction shown above? (Show your work for each set
of coefficients.)
A 2, 1, 2, 1
B 2, 2, 1, 1
C 2, 1, 2, 2
D 2, 2, 2, 1