Stoichiometry and Chemical Calculations MCQs 2026

One mole of any substance contains ___ particles

1. A6.022×10^22✓
2. B3.011×10^23✓
3. C1×10^23✓
4. D6.022×10^23✓

The molar mass of water (H2O) is

1. A16 g/mol✓
2. B20 g/mol✓
3. C18 g/mol✓
4. D17 g/mol✓

The number of moles in 44 g of CO2 (molar mass 44 g/mol) is

1. A0.5 mol✓
2. B2 mol✓
3. C4 mol✓
4. D1 mol✓

The mass of 2 moles of NaOH (molar mass 40 g/mol) is

1. A80 g✓
2. B40 g✓
3. C20 g✓
4. D100 g✓

The number of atoms in 1 mole of helium gas is

1. A3.011×10^23✓
2. B12.044×10^23✓
3. C1×10^23✓
4. D6.022×10^23✓

Avogadro's number is approximately

1. A3.14×10^23✓
2. B6.022×10^23✓
3. C9.8×10^23✓
4. D1.6×10^-19✓

The volume occupied by 1 mole of an ideal gas at STP is

1. A24 L✓
2. B25 L✓
3. C20 L✓
4. D22.4 L✓

The empirical formula represents

1. AThe simplest whole-number ratio of atoms in a compound✓
2. BThe exact number of atoms in one molecule✓
3. CThe molar mass of the compound✓
4. DThe number of moles present✓

The molecular formula of a compound is always

1. AA whole-number multiple of the empirical formula✓
2. BSmaller than the empirical formula✓
3. CUnrelated to the empirical formula✓
4. DEqual to half the empirical formula✓

If the empirical formula of a compound is CH2O and its molar mass is 180 g/mol, its molecular formula is

1. AC2H4O2✓
2. BC3H6O3✓
3. CC6H12O6✓
4. DCH2O✓

The percentage composition of an element in a compound is calculated as

1. A(Mass of element in one mole ÷ Molar mass of compound) × 100✓
2. B(Moles of compound ÷ Avogadro's number) × 100✓
3. CAtomic mass ÷ 100✓
4. DMolar mass ÷ mass of element✓

The percentage of oxygen by mass in water (H2O, molar mass 18) is approximately

1. A88.9%✓
2. B11.1%✓
3. C50%✓
4. D66.7%✓

The limiting reagent in a reaction is the reactant that

1. AIs present in excess✓
2. BDoes not react✓
3. CIs completely consumed first, limiting the amount of product✓
4. DHas the highest molar mass✓

The reactant that remains after a reaction is complete is called the

1. AExcess reagent✓
2. BLimiting reagent✓
3. CCatalyst✓
4. DProduct✓

Theoretical yield refers to

1. AThe actual amount of product obtained in the lab✓
2. BThe percentage of reactant used✓
3. CThe maximum amount of product predicted by stoichiometric calculation✓
4. DThe amount of limiting reagent✓

Percentage yield is calculated as

1. ATheoretical yield ÷ molar mass × 100✓
2. B(Actual yield ÷ Theoretical yield) × 100✓
3. C(Theoretical yield ÷ Actual yield) × 100✓
4. DActual yield × molar mass✓

A balanced chemical equation obeys the law of

1. ADefinite proportions only✓
2. BMultiple proportions only✓
3. CAvogadro's law✓
4. DConservation of mass✓

In the reaction N2 + 3H2 → 2NH3, the mole ratio of H2 to NH3 is

1. A1:1✓
2. B1:2✓
3. C2:3✓
4. D3:2✓

The formula weight of MgO (Mg=24, O=16) is

1. A32✓
2. B40✓
3. C56✓
4. D48✓

The number of moles of oxygen atoms in 2 moles of CO2 is

1. A4 mol✓
2. B2 mol✓
3. C1 mol✓
4. D6 mol✓

Molarity of a solution is defined as

1. AMoles of solute per kg of solvent✓
2. BMoles of solute per liter of solution✓
3. CGrams of solute per liter of solution✓
4. DMoles of solvent per liter of solution✓

The molarity of a solution containing 2 moles of NaCl in 500 mL of solution is

1. A1 M✓
2. B0.5 M✓
3. C2 M✓
4. D4 M✓

Molality of a solution is defined as

1. AMoles of solute per liter of solution✓
2. BGrams of solute per liter of solvent✓
3. CMoles of solvent per kg of solute✓
4. DMoles of solute per kilogram of solvent✓

The number of moles of solute in 250 mL of a 2 M solution is

1. A1 mol✓
2. B0.5 mol✓
3. C2 mol✓
4. D0.25 mol✓

The mass of 0.25 mol of CaCO3 (molar mass 100 g/mol) is

1. A100 g✓
2. B4 g✓
3. C25 g✓
4. D50 g✓

The molar mass of glucose, C6H12O6, is

1. A180 g/mol✓
2. B162 g/mol✓
3. C194 g/mol✓
4. D176 g/mol✓

The number of moles present in 11.2 L of a gas at STP is

1. A1 mol✓
2. B2 mol✓
3. C0.25 mol✓
4. D0.5 mol✓

According to the law of conservation of mass, in a chemical reaction the total mass of reactants

1. AIncreases✓
2. BEquals the total mass of products✓
3. CDecreases✓
4. DBecomes zero✓

The law of definite proportions states that a chemical compound always contains the same elements

1. AIn variable proportions by mass✓
2. BIn fixed proportions by mass✓
3. CIn equal number of moles only✓
4. DOnly in the gaseous state✓

The law of multiple proportions applies when two elements form

1. AOnly one compound✓
2. BIonic compounds only✓
3. CMore than one compound, with masses in small whole-number ratios✓
4. DIsotopes✓

The number of moles of NaOH needed to completely neutralize 1 mole of H2SO4 is

1. A1 mol✓
2. B0.5 mol✓
3. C2 mol✓
4. D3 mol✓

In the reaction 2H2 + O2 → 2H2O, the number of moles of water produced from 4 moles of H2 (excess O2) is

1. A2 mol✓
2. B1 mol✓
3. C4 mol✓
4. D8 mol✓

A 1 molar solution of a substance contains how many moles of solute per liter

1. A0.5 mol✓
2. B1 mol✓
3. C2 mol✓
4. D10 mol✓

Which quantity remains constant during a chemical reaction, per the law of conservation of mass

1. ATotal mass✓
2. BVolume of gas only✓
3. CNumber of moles of gas✓
4. DTemperature✓

The formula mass of Na2CO3 (Na=23, C=12, O=16) is

1. A84✓
2. B106✓
3. C90✓
4. D62✓

The percentage of carbon by mass in CO2 (molar mass 44) is approximately

1. A50%✓
2. B12%✓
3. C27.3%✓
4. D73%✓

In stoichiometric calculations, mole ratios are obtained directly from the

1. AAtomic masses✓
2. BCoefficients of the balanced equation✓
3. CMolar volumes✓
4. DPercentage composition✓

If 5 moles of a limiting reagent produce 5 moles of product in a 1:1 reaction and only 4 moles of product were actually obtained, the percentage yield is

1. A100%✓
2. B125%✓
3. C80%✓
4. D50%✓

A solution containing 1 mole of solute dissolved in exactly 1 kg of solvent has a molality of

1. A0.5 m✓
2. B1 m✓
3. C2 m✓
4. D10 m✓

The relative formula mass of a compound is the sum of the

1. AAtomic numbers of all atoms✓
2. BNumber of moles of each element✓
3. CCharges of all ions✓
4. DRelative atomic masses of all atoms in the formula✓

Which of the following best describes an empirical formula determination experiment

1. AMeasuring the boiling point of a compound✓
2. BMeasuring the volume of gas released✓
3. CTitrating an acid with a base✓
4. DFinding the mass ratio of elements combined in a compound✓

The number of moles of ions produced when 1 mole of Na2SO4 fully dissociates in water is

1. A1 mol✓
2. B2 mol✓
3. C4 mol✓
4. D3 mol✓

The mass percent of hydrogen in methane, CH4 (molar mass 16 g/mol) is approximately

1. A12.5%✓
2. B20%✓
3. C25%✓
4. D75%✓

1 mole of a diatomic gas at STP occupies a volume of

1. A22.4 L✓
2. B11.2 L✓
3. C44.8 L✓
4. D6.022 L✓

How many moles of oxygen gas (O2) are required to completely combust 1 mole of methane (CH4 + 2O2 → CO2 + 2H2O)

1. A1 mol✓
2. B2 mol✓
3. C3 mol✓
4. D0.5 mol✓

The number of grams in 0.5 mole of oxygen gas, O2 (molar mass 32 g/mol) is

1. A32 g✓
2. B16 g✓
3. C8 g✓
4. D64 g✓

Gram atomic mass is the mass, in grams, of

1. AOne mole of atoms of an element✓
2. BOne atom of an element✓
3. COne molecule of a compound✓
4. DOne ion of an element✓

The number of moles of electrons required to reduce 1 mole of Al3+ to Al metal is

1. A3 mol✓
2. B1 mol✓
3. C2 mol✓
4. D6 mol✓

Stoichiometry is fundamentally based on the relationship between

1. ATemperature and pressure of gases only✓
2. BEnthalpy and entropy✓
3. CAtomic radius and ionization energy✓
4. DMoles of reactants and products in a balanced equation✓

The number of moles in 9 g of water (molar mass 18 g/mol) is

1. A1 mol✓
2. B0.25 mol✓
3. C0.5 mol✓
4. D2 mol✓