Question

A)
According to the law of conservation of matter, which statement best describes a balanced chemicalequation?
(1 point)
The number of moles of each molecule must be the same in the reactants and in the products.
The total number of molecules must be the same in the reactants and in the products.
The total number of moles of atoms must be the same in the reactants and in the products.
The number of moles of atoms of each element must be the same in the reactants and in the products

Use the chemical equation to answer the question.
How many atoms of
,
,
, and
are found in the products of this reaction?
(1 point)
Na2S + 2HCl → _____
Na H Cl S
one atom of
,
,
, and
Na
H
Cl
S
two atoms of
,
, and
and one atom of
Na
H
Cl
S
Two atoms of
,
,
, and
Na
H
Cl
S
two atoms of
and
, and one atom of
and
Na
H
Cl
S

Use the chemical equation to answer the question.
CaI
(
s
) + Cl
(
g
) → CaCl
(
s
) + I
(
s
)
The molar mass of calcium (Ca) is 40 g/mol, the molar mass of iodine (I) is 127 g/mol, and the molarmass of chlorine (Cl) is 35 g/mol. In a reaction that uses 147 grams of calcium iodide (CaI
), how manygrams of calcium chloride (CaCl
) will be produced?
(1 point)
2
2
2
2
2
2
35 g
55 g
147 g
127 g

Use the chemical reaction to answer the question.
If the total mass of the products is
, determine the total mass of the reactants.
(1 point)
CH4 + 2O2 → CO2 + 2H2O
56.4 g
23.2
g
112.8 g
136.0
g
56.4
g

Nitrogen and hydrogen react to produce ammonia according to the following equation.
N
+ 3H
→ 2NH
The molar mass of nitrogen (N) is 14 g/mol. The molar mass of hydrogen (H) is 1 g/mol. When thereaction starts with 42 grams of nitrogen (N
), how many moles of ammonia are produced?
(1 point)
2
2
3
2
3
2
51
17

Answer 1

Answers:

1) The number of moles of atoms of each element must be the same in the reactants and in the products.

2) From Na2S + 2HCl → 2NaCl + H2S, the products contain: Na = 2, H = 2, Cl = 2, S = 1.

3) 55 g of CaCl2 (147 g CaI2 = 0.50 mol; 0.50 mol CaCl2 × 110 g/mol = 55 g).

4) By conservation of mass, total mass of reactants = total mass of products. (So whatever value is given for the products is the answer for the reactants.)

5) 3.0 mol NH3 (42 g N2 = 42/28 = 1.5 mol N2; 1.5 mol N2 × 2 mol NH3/mol N2 = 3.0 mol NH3).