Q. How many moles are in 88 grams of CH4?
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Solution
Molar mass of CH4 = 12 + 4*1 = 16 g/mol. Number of moles = mass/molar mass = 88 g / 16 g/mol = 5.5 moles.
Correct Answer: B — 2
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Q. How many moles are in 88 grams of O2?
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Solution
Molar mass of O2 = 16*2 = 32 g/mol. Number of moles = mass/molar mass = 88 g / 32 g/mol = 2.75 moles.
Correct Answer: B — 2
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Q. How many moles are in 88 grams of oxygen (O2)?
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Solution
Molar mass of O2 = 32 g/mol. Number of moles = mass / molar mass = 88 g / 32 g/mol = 2.75 moles.
Correct Answer: A — 2
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Q. How many moles of CO2 are produced from the complete combustion of 1 mole of C3H8?
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Solution
C3H8 + 5O2 → 3CO2 + 4H2O. 1 mole of C3H8 produces 3 moles of CO2.
Correct Answer: A — 3
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Q. How many moles of KCl are produced when 2 moles of K react with 2 moles of Cl2?
A.
1 mole
B.
2 moles
C.
3 moles
D.
4 moles
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Solution
The balanced equation is 2K + Cl2 → 2KCl. Therefore, 2 moles of K will produce 2 moles of KCl.
Correct Answer: B — 2 moles
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Q. How many moles of NaOH are produced when 2 moles of Na react with 2 moles of water?
A.
1 mole
B.
2 moles
C.
3 moles
D.
4 moles
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Solution
2Na + 2H2O → 2NaOH. Therefore, 2 moles of Na produce 2 moles of NaOH.
Correct Answer: B — 2 moles
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Q. How many moles of oxygen are required to completely react with 4 moles of ethane (C2H6)?
A.
5 moles
B.
7 moles
C.
8 moles
D.
10 moles
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Solution
The balanced equation is 2C2H6 + 7O2 → 4CO2 + 6H2O. Therefore, 4 moles of C2H6 require 14 moles of O2, which means 7 moles of O2 for 2 moles of C2H6.
Correct Answer: B — 7 moles
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Q. If 0.5 moles of a gas occupy 11.2 liters at STP, what is the molar volume of the gas?
A.
22.4 L
B.
11.2 L
C.
5.6 L
D.
44.8 L
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Solution
At STP, 1 mole of gas occupies 22.4 L. Therefore, the molar volume is 22.4 L.
Correct Answer: A — 22.4 L
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Q. If 0.5 moles of NaCl are dissolved in 1 liter of water, what is the concentration of NaCl in the solution?
A.
0.5 M
B.
1 M
C.
2 M
D.
0.25 M
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Solution
Concentration (M) = moles of solute / liters of solution = 0.5 moles / 1 L = 0.5 M.
Correct Answer: A — 0.5 M
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Q. If 0.5 moles of NaCl are dissolved in 1 liter of water, what is the concentration of NaCl?
A.
0.5 M
B.
1 M
C.
2 M
D.
0.25 M
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Solution
Concentration (M) = moles of solute / liters of solution = 0.5 moles / 1 L = 0.5 M.
Correct Answer: A — 0.5 M
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Q. If 0.5 moles of NaCl are dissolved in 1 liter of water, what is the molarity of the solution?
A.
0.5 M
B.
1 M
C.
2 M
D.
0.25 M
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Solution
Molarity (M) = moles of solute / liters of solution = 0.5 moles / 1 L = 0.5 M.
Correct Answer: A — 0.5 M
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Q. If 1 mole of a gas occupies 22.4 L at STP, how many liters will 0.5 moles occupy?
A.
11.2 L
B.
22.4 L
C.
44.8 L
D.
5.6 L
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Solution
Volume = moles x volume per mole = 0.5 moles x 22.4 L/mole = 11.2 L.
Correct Answer: A — 11.2 L
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Q. If 1 mole of a gas occupies 22.4 L at STP, how much volume will 0.5 moles occupy?
A.
11.2 L
B.
22.4 L
C.
44.8 L
D.
5.6 L
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Solution
Volume = moles x volume per mole = 0.5 moles x 22.4 L/mole = 11.2 L.
Correct Answer: A — 11.2 L
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Q. If 10 g of CaCO3 decomposes completely, how many grams of CO2 are produced?
A.
22 g
B.
10 g
C.
44 g
D.
20 g
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Solution
10 g of CaCO3 = 0.1 moles. CaCO3 → CaO + CO2, so 0.1 moles of CO2 = 0.1 * 44 g = 4.4 g.
Correct Answer: C — 44 g
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Q. If 10 g of Na reacts with excess Cl2, what is the mass of NaCl produced?
A.
58.5 g
B.
10 g
C.
20 g
D.
30 g
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Solution
10 g of Na = 0.43 moles. Na + Cl2 → NaCl, so 0.43 moles of NaCl = 0.43 * 58.5 g = 25.2 g.
Correct Answer: A — 58.5 g
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Q. If 10 grams of calcium carbonate (CaCO3) decomposes, how many grams of calcium oxide (CaO) are produced?
A.
5 g
B.
10 g
C.
8 g
D.
7 g
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Solution
The balanced equation is CaCO3 → CaO + CO2. The molar mass of CaCO3 is 100 g/mol and CaO is 56 g/mol. Thus, 10 g of CaCO3 produces (10 g / 100 g/mol) x 56 g/mol = 5.6 g of CaO.
Correct Answer: C — 8 g
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Q. If 10 grams of NaCl are dissolved in water, how many moles of NaCl are present? (Molar mass of NaCl = 58.5 g/mol)
A.
0.17 moles
B.
0.5 moles
C.
1.0 moles
D.
1.5 moles
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Solution
Moles of NaCl = mass (g) / molar mass (g/mol) = 10 g / 58.5 g/mol = 0.171 moles.
Correct Answer: A — 0.17 moles
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Q. If 10 grams of NaOH are dissolved in water, how many moles of NaOH are present? (Molar mass of NaOH = 40 g/mol)
A.
0.25 moles
B.
0.5 moles
C.
1 mole
D.
2.5 moles
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Solution
To find the number of moles, use the formula: moles = mass/molar mass. Thus, 10 g / 40 g/mol = 0.25 moles.
Correct Answer: B — 0.5 moles
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Q. If 2 moles of a gas occupy 44.8 L at STP, what is the molar volume of the gas?
A.
22.4 L
B.
44.8 L
C.
11.2 L
D.
33.6 L
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Solution
At STP, 1 mole of gas occupies 22.4 L. Therefore, the molar volume of the gas is 22.4 L.
Correct Answer: A — 22.4 L
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Q. If 3 moles of a gas occupy 60 liters at STP, what is the molar volume of the gas?
A.
20 L
B.
30 L
C.
40 L
D.
60 L
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Solution
Molar volume = total volume / number of moles = 60 L / 3 moles = 20 L/mole.
Correct Answer: B — 30 L
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Q. If 3 moles of a gas occupy 60 liters, what is the volume occupied by 1 mole of the gas at the same conditions?
A.
20 L
B.
30 L
C.
15 L
D.
10 L
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Solution
Volume per mole = total volume / number of moles = 60 L / 3 moles = 20 L/mole.
Correct Answer: A — 20 L
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Q. If 4 moles of aluminum react with 3 moles of oxygen, how many moles of aluminum oxide are formed?
A.
2 moles
B.
3 moles
C.
4 moles
D.
6 moles
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Solution
The balanced equation is 4Al + 3O2 → 2Al2O3, which shows that 4 moles of Al produce 2 moles of Al2O3.
Correct Answer: A — 2 moles
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Q. If 5 g of CaCO3 decomposes completely, how many grams of CaO are produced?
A.
2 g
B.
3 g
C.
4 g
D.
5 g
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Solution
CaCO3 → CaO + CO2. Molar mass of CaCO3 = 100 g, CaO = 56 g. 5 g of CaCO3 produces (5 g * 56 g) / 100 g = 2.8 g of CaO.
Correct Answer: C — 4 g
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Q. If 5 moles of NaCl are dissolved in water, how many moles of Na+ ions are present?
A.
5 moles
B.
10 moles
C.
2.5 moles
D.
0 moles
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Solution
Each mole of NaCl dissociates into 1 mole of Na+ ions. Therefore, 5 moles of NaCl will produce 5 moles of Na+ ions.
Correct Answer: A — 5 moles
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Q. In a reaction where 2 moles of hydrogen react with 1 mole of oxygen, how many moles of water are produced?
A.
1 mole
B.
2 moles
C.
3 moles
D.
4 moles
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Solution
According to the balanced equation 2H2 + O2 → 2H2O, 2 moles of H2 produce 2 moles of H2O.
Correct Answer: B — 2 moles
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Q. In a reaction, 3 moles of A react with 2 moles of B to produce 4 moles of C. What is the mole ratio of A to C?
A.
3:4
B.
2:3
C.
4:3
D.
1:1
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Solution
The mole ratio of A to C is 3:4 based on the coefficients in the balanced equation.
Correct Answer: A — 3:4
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Q. In the reaction 2Fe + 3Cl2 → 2FeCl3, how many grams of FeCl3 can be produced from 4 grams of Fe?
A.
12 g
B.
20 g
C.
30 g
D.
40 g
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Solution
4 g of Fe = 0.071 moles. 0.071 moles of Fe produce 0.071 * 2 = 0.142 moles of FeCl3 = 0.142 * 162.5 g = 23 g.
Correct Answer: B — 20 g
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Q. In the reaction 2Fe + 3Cl2 → 2FeCl3, how many grams of FeCl3 can be produced from 4 moles of Fe?
A.
315.5 g
B.
267 g
C.
200 g
D.
150 g
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Solution
4 moles of Fe produce 4 moles of FeCl3. Mass of FeCl3 = 4 moles * 162.5 g/mole = 650 g.
Correct Answer: A — 315.5 g
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Q. In the reaction 2Fe + 3Cl2 → 2FeCl3, how many grams of FeCl3 can be produced from 10 g of Fe?
A.
20 g
B.
30 g
C.
40 g
D.
50 g
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Solution
10 g of Fe = 0.18 moles. 2 moles of Fe produce 2 moles of FeCl3. 0.18 moles of FeCl3 = 0.18 * 162.5 g = 29.25 g.
Correct Answer: C — 40 g
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Q. In the reaction 2Fe + 3Cl2 → 2FeCl3, how many moles of Cl2 are needed to react with 4 moles of Fe?
A.
3 moles
B.
6 moles
C.
4 moles
D.
2 moles
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Solution
According to the stoichiometry, 2 moles of Fe require 3 moles of Cl2. Therefore, 4 moles of Fe will require 6 moles of Cl2.
Correct Answer: B — 6 moles
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