Stoikiometri Practice Questions
UN (Indonesia) · UN Kimia · 132 free MCQs with instant results and detailed explanations.
132
Total
29
Easy
73
Medium
30
Hard
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Sample Questions from Stoikiometri
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Q1
Easy
What is the molar mass of water (H2O)?
A.
18 g/mol
B.
16 g/mol
C.
20 g/mol
D.
15 g/mol
Show Answer & Explanation
Correct Answer: A
The molar mass of water is calculated by adding the atomic masses of its constituent elements: H (1 g/mol) and O (16 g/mol). So, 2(1) + 16 = 18 g/mol.
Q2
Easy
If 4 moles of sodium (Na) react with excess chlorine (Cl2), how many moles of sodium chloride (NaCl) will be produced?
A.
4 moles
B.
2 moles
C.
8 moles
D.
1 mole
Show Answer & Explanation
Correct Answer: A
The balanced reaction is 2Na + Cl2 → 2NaCl. This means 2 moles of sodium produce 2 moles of sodium chloride. Therefore, 4 moles of sodium will produce 4 moles of NaCl.
Q3
Easy
In a reaction where 2 moles of hydrogen gas react with 1 mole of oxygen gas, how many moles of water are produced?
A.
1 mole
B.
2 moles
C.
3 moles
D.
4 moles
Show Answer & Explanation
Correct Answer: B
According to the balanced equation 2H₂ + O₂ → 2H₂O, 2 moles of hydrogen and 1 mole of oxygen produce 2 moles of water.
Q4
Medium
What is the molar mass of calcium carbonate (CaCO3)?
A.
100 g/mol
B.
94 g/mol
C.
80 g/mol
D.
120 g/mol
Show Answer & Explanation
Correct Answer: A
The molar mass of calcium carbonate is calculated by adding the atomic masses of calcium (40 g/mol), carbon (12 g/mol), and oxygen (16 g/mol × 3 = 48 g/mol). Thus, 40 + 12 + 48 = 100 g/mol.
Q5
Medium
If 5 moles of nitrogen gas react with excess hydrogen gas, how many moles of ammonia (NH3) can be produced?
A.
5 moles
B.
10 moles
C.
15 moles
D.
20 moles
Show Answer & Explanation
Correct Answer: B
The balanced equation for the reaction is N2 + 3H2 → 2NH3. From this, 1 mole of N2 produces 2 moles of NH3. Therefore, 5 moles of N2 will produce 5 * 2 = 10 moles of NH3.
Q6
Medium
In the decomposition of potassium chlorate (KClO3), what is the ratio of moles of oxygen gas (O2) produced to moles of KClO3 decomposed?
A.
1:1
B.
1:2
C.
2:2
D.
3:2
Show Answer & Explanation
Correct Answer: B
The balanced equation for the decomposition is 2KClO3 → 2KCl + 3O2. Therefore, 2 moles of KClO3 produce 3 moles of O2, resulting in a mole ratio of 1:1.5 or simplified as 1:2.
Q7
Medium
A reaction produces 4 moles of product from 2 moles of reactant A. What is the yield percentage if 3 moles of product are obtained?
A.
50%
B.
75%
C.
80%
D.
100%
Show Answer & Explanation
Correct Answer: B
Yield percentage is calculated as (actual yield / theoretical yield) × 100%. The theoretical yield is 4 moles (from 2 moles of A), and the actual yield is 3 moles. Thus, the yield percentage is (3/4) × 100% = 75%.
Q8
Hard
In a reaction where 4 moles of A react with 3 moles of B to produce 2 moles of C and 2 moles of D, what is the limiting reagent if 6 moles of A and 5 moles of B are available?
A.
A
B.
B
C.
C
D.
D
Show Answer & Explanation
Correct Answer: B
To determine the limiting reagent, we compare the mole ratios required by the reaction. For 4 moles of A, 3 moles of B are needed. With 6 moles of A, we can use: (6 moles A) * (3 moles B / 4 moles A) = 4.5 moles B. However, only 5 moles of B are available, which is more than required by the available A. Thus, B is limiting.
Q9
Hard
A mixture contains 10 grams of sodium chloride (NaCl) and 20 grams of potassium bromide (KBr). How many grams of sodium bromide (NaBr) can be produced if they react completely?
A.
22 grams
B.
30 grams
C.
28 grams
D.
24 grams
Show Answer & Explanation
Correct Answer: A
The balanced reaction is: NaCl + KBr → NaBr + KCl. From the molar masses, NaCl (58.44 g/mol) and KBr (119 g/mol) produce NaBr (102.89 g/mol). Calculate moles of NaCl and KBr, then find the limiting reagent and use it to determine the mass of NaBr produced.
Q10
Hard
A solution contains 0.5 moles of sodium chloride (NaCl) dissolved in 1 liter of water. If 0.2 moles of NaCl are added, what will be the new concentration of the solution in moles per liter?
A.
0.3 M
B.
0.5 M
C.
0.7 M
D.
0.2 M
Show Answer & Explanation
Correct Answer: C
The initial concentration is 0.5 M from 0.5 moles in 1 L. After adding 0.2 moles, the total moles become 0.7 in 1 L. Therefore, the new concentration is 0.7 M.
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Stoikiometri — UN (Indonesia) UN Kimia Practice Questions Online
This page contains 132 practice MCQs for the chapter Stoikiometri in UN (Indonesia) UN Kimia. The questions are organized by difficulty — 29 easy, 73 medium, 30 hard — so you can choose the right level for your preparation.
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