Question

Question
1
Question
2
A)
Which option correctly describes the reactants and products of a chemical reaction?
(1 point)
The mass of the reactants can be more or less than the mass of the products. The total number of moles ofthe reactants can also be more or less than the total number of moles of the products.
The mass of the reactants must be equal to the mass of the products. The total number of moles of thereactants must also be equal to the total number of moles of the products.
The mass of the reactants must be equal to the mass of the products. The total number of moles of thereactants can be more or less than the total number of moles of the products.
The mass of the reactants can be more or less than the mass of the products. The total number of moles ofthe reactants must be equal to the total number of moles of the products.
A)
A student knows the mass of one of the reactants of a chemical reaction and wants to calculate themass of one of the products of the reaction. Which process should the student follow?
(1 point)
Divide the mass of the reactant by its molar mass to find the number of moles of the reactant. Use thechemical equation to find the number of moles of the product. Multiply the number of moles of the productby its molar mass to find the mass of the product.
Multiply the mass of the reactant by its molar mass to find the number of moles of the reactant. Use thechemical equation to find the number of moles of the product. Divide the number of moles of the product byits molar mass to find the mass of the product.
Divide the mass of the reactant by its molar mass to find the number of moles of the reactant. Use thechemical equation to find the number of moles of the product. Divide the number of moles of the product byits molar mass to find the mass of the product.
Multiply the mass of the reactant by its molar mass to find the number of moles of the reactant. Use thechemical equation to find the number of moles of the product. Multiply the number of moles of the productby its molar mass to find the mass of the product.
Question
3
Question
4
A)
Use the chemical equation to answer the question.
2Ag(
s
) + H
S(
g
) → Ag
S(
s
) + H
(
g
)
The molar mass of silver (Ag) is 108 g/mol. The molar mass of sulfur (S) is 32 g/mol. The reaction uses0.04 mol of silver. Which steps show how to determine the mass of silver sulfide (Ag
S) produced in thereaction?
(1 point)
2
2
2
2
;
108
g/mol
+
2
(
32
g/mol
)
=
172
g/mol
(
172
g/mol
)
(
0.04
mol
)
=
6.88
g
;
108
g/mol
+
2
(
32
g/mol
)
=
172
g/mol
(
172
g/mol
)
(
0.02
mol
)
=
3.44
g
;
2
(
108
g/mol
)
+
32
g/mol
=
248
g/mol
(
248
g/mol
)
(
0.04
mol
)
=
9.92
g
;
2
(
108
g/mol
)
+
32
g/mol
=
248
g/mol
(
248
g/mol
)
(
0.02
mol
)
=
4.96
g
A)
Use the chemical equation to answer the question.
4K(
s
) + O
(
g
) → 2K
O(
s
)
The molar mass of potassium (K) is 39 g/mol. The molar mass of oxygen (O) is 16 g/mol. How manygrams of potassium are needed in the reaction to produce 23.5 grams of potassium oxide (K
O)?
(1 point)
2
2
2
0.50 g
19.5 g
23.5 g
9.75 g
Question
5
A)
Use the chemical equation and the table to answer the question.
Pb(NO
)
(
aq
) + 2KBr(
aq
) → PbBr
(
s
) + 2KNO
(
aq
)
Molar Mass (g/mol) of Reactants andProducts Involved in a Reaction
Reactant or Product
Molar Mass (g/mol)
Pb(NO
)
331
KBr
119
PbBr
367
KNO
101
When 496.5 grams of Pb(NO
)
reacts completely with KBr, how much will the total mass of theproducts be?
(1 point)
3
2
2
3
3
2
2
3
3
2
550.5 g
702.0 g
853.5 g
496.5 g

Answer 1

Here are the answers with brief reasons:

Question 1
- Correct choice: "The mass of the reactants must be equal to the mass of the products. The total number of moles of the reactants can be more or less than the total number of moles of the products."
- Reason: Mass is conserved; mole counts can change according to stoichiometric coefficients.

Question 2
- Correct choice: "Divide the mass of the reactant by its molar mass to find the number of moles of the reactant. Use the chemical equation to find the number of moles of the product. Multiply the number of moles of the product by its molar mass to find the mass of the product."
- Reason: Mass → moles → mole ratio → moles → mass.

Question 3
- Correct choice: "2(108 g/mol) + 32 g/mol = 248 g/mol (248 g/mol)(0.02 mol) = 4.96 g."
- Reason: 2 Ag → 1 Ag2S, so 0.04 mol Ag gives 0.02 mol Ag2S; mass = 0.02 × 248 = 4.96 g.

Question 4
- Correct choice: 19.5 g.
- Reason: Molar mass K2O = 94 g/mol; moles K2O = 23.5/94 = 0.25 mol. Need 2 mol K per mol K2O → 0.50 mol K → mass = 0.50 × 39 = 19.5 g.

Question 5
- Correct choice: 853.5 g.
- Reason: 496.5 g Pb(NO3)2 = 1.5 mol → produces 1.5 mol PbBr2 (1.5×367 = 550.5 g) and 3.0 mol KNO3 (3.0×101 = 303 g). Total products = 550.5 + 303 = 853.5 g.