Quantitative Chemistry questions

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Quantitative Chemistry question collection

Review Quantitative Chemistry questions for Chemistry, with correct answers shown and coverage across relative formula mass; moles and reacting masses; concentration calculations.

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Question 1

Why can measured mass fall when magnesium reacts with acid in an open flask?
  1. Hydrogen gas escapes
  2. Atoms are destroyed
  3. The balance subtracts liquid mass
  4. Magnesium gains negative mass

Question 2

Which equation is correctly balanced?
  1. \(\mathrm{Mg} + 2\mathrm{HCl} \to \mathrm{MgCl}_{2} + \mathrm{H}_{2}\)
  2. \(\mathrm{Mg} + \mathrm{HCl} \to \mathrm{MgCl} + \mathrm{H}_{2}\)
  3. \(2\mathrm{Mg} + \mathrm{HCl} \to \mathrm{MgCl}_{2} + \mathrm{H}_{2}\)
  4. \(\mathrm{Mg} + 2\mathrm{HCl} \to \mathrm{MgCl} + \mathrm{H}_{2}\)

Question 3

What is the relative formula mass, Mr, of CaCO3? (Ca = \(40\), C = \(12\), O = \(16\))?
  1. \(100\)
  2. \(84\)
  3. \(88\)
  4. \(116\)

Question 4

What is the Mr of MgCl2? (Mg = \(24\), Cl = \(35.5\))?
  1. \(95\)
  2. \(71\)
  3. \(59.5\)
  4. \(119\)

Question 5

What is the percentage by mass of oxygen in MgO? (Mg = \(24\), O = \(16\))?
  1. \(40\%\)
  2. \(60\%\)
  3. \(25\%\)
  4. \(16\%\)

Question 6

What is the percentage by mass of carbon in CO2? (C = \(12\), O = \(16\))?
  1. \(27.3\%\)
  2. \(12\%\)
  3. \(44\%\)
  4. \(72.7\%\)

Question 7

What is \(250\,\mathrm{cm^3}\) in \(\mathrm{dm^3}\)?
  1. \(0.250\,\mathrm{dm^3}\)
  2. \(2.50\,\mathrm{dm^3}\)
  3. \(25.0\,\mathrm{dm^3}\)
  4. \(0.025\,\mathrm{dm^3}\)

Question 8

How much solute is needed to make \(0.50\,\mathrm{dm^3}\) of a \(20\,\mathrm{g\,dm^{-3}}\) solution?
  1. \(10\,\mathrm{g}\)
  2. \(40\,\mathrm{g}\)
  3. \(0.04\,\mathrm{g}\)
  4. \(20\,\mathrm{g}\)

Question 9

\(5.0\,\mathrm{g}\) of salt are dissolved to make \(200\,\mathrm{cm^3}\) solution. What is the concentration in \(\mathrm{g\,dm^{-3}}\)?
  1. \(25\,\mathrm{g\,dm^{-3}}\)
  2. \(2.5\,\mathrm{g\,dm^{-3}}\)
  3. \(10\,\mathrm{g\,dm^{-3}}\)
  4. \(250\,\mathrm{g\,dm^{-3}}\)

Question 10

What identifies the limiting reactant?
  1. It is used up first and stops more product forming
  2. It has the largest starting mass
  3. It has the first coefficient in the equation
  4. It speeds the reaction without being consumed

Question 11

\(\mathrm{CaCO}_3 \to \mathrm{CaO} + \mathrm{CO}_2\). If \(25\,\mathrm{g}\) of \(\mathrm{CaCO}_3\) decomposes completely, what mass of \(\mathrm{CO}_2\) is formed? (Mr: \(\mathrm{CaCO}_3 = 100\), \(\mathrm{CO}_2 = 44\))?
  1. \(11\,\mathrm{g}\)
  2. \(4.4\,\mathrm{g}\)
  3. \(22\,\mathrm{g}\)
  4. \(44\,\mathrm{g}\)

Question 12

A reaction has a theoretical yield of \(8.0\,\mathrm{g}\) and an actual yield of \(6.0\,\mathrm{g}\). What is the percentage yield?
  1. \(75\%\)
  2. \(133\%\)
  3. \(25\%\)
  4. \(48\%\)

Question 13

Which can make percentage yield less than 100%?
  1. Losing product during separation
  2. Using a balanced symbol equation
  3. Calculating relative formula masses
  4. Adding a catalyst that remains unchanged

Question 14

What does atom economy measure?
  1. Percentage of reactant mass in the desired product
  2. Percentage of theoretical product actually obtained
  3. Percentage by mass of one element
  4. Product mass made per second

Question 15

What volume does one mole of gas occupy at room conditions?
  1. \(24\,\mathrm{dm^3}\)
  2. \(2.4\,\mathrm{dm^3}\)
  3. \(240\,\mathrm{dm^3}\)
  4. \(12\,\mathrm{dm^3}\)

Question 16

\(0.50\,\mathrm{mol}\) of gas at RTP has what volume?
  1. \(12\,\mathrm{dm^3}\)
  2. \(24\,\mathrm{dm^3}\)
  3. \(6\,\mathrm{dm^3}\)
  4. \(48\,\mathrm{dm^3}\)

Question 17

What is one mole?
  1. The amount containing Avogadro’s number of particles
  2. The mass of one gram of a substance
  3. The number of atoms in one molecule
  4. The volume of one litre of gas

Question 18

Which equation gives moles from mass and relative formula mass?
  1. \(n=\frac{m}{M_r}\)
  2. \(n=mM_r\)
  3. \(n=\frac{M_r}{m}\)
  4. \(n=m+M_r\)

Question 19

Which unit is used for amount concentration?
  1. mol dm⁻³
  2. g dm⁻³
  3. mol
  4. dm³

Question 20

What is the equation for concentration?
  1. \(c=\frac{n}{V}\)
  2. \(c=nV\)
  3. \(c=\frac{V}{n}\)
  4. \(c=n+V\)

Question 21

Which ratio defines percentage yield?
  1. Actual yield divided by theoretical yield
  2. Theoretical yield divided by actual yield
  3. Desired product mass divided by reactant mass
  4. Solute mass divided by solution volume

Question 22

What is theoretical yield?
  1. Maximum product predicted from the reacting amounts
  2. Product actually collected after separation
  3. Reactant left after the reaction stops
  4. Waste predicted by atom economy

Question 23

What does an empirical formula show?
  1. Simplest whole-number ratio of atoms
  2. Actual number of atoms in one molecule
  3. Percentage of atoms in the desired product
  4. Total mass of one mole of compound

Question 24

Which ratio is used to calculate percentage uncertainty?
  1. Absolute uncertainty divided by measured value
  2. Measured value divided by absolute uncertainty
  3. Actual yield divided by theoretical yield
  4. Mass divided by volume

Question 25

What happens to an excess reactant?
  1. Some remains when the reaction stops
  2. It is used up before the limiting reactant
  3. It becomes a catalyst
  4. It determines the maximum product alone

Question 26

A reaction uses 2 mol of hydrogen for each 1 mol of oxygen. What is the balancing ratio?
  1. 2:1
  2. 1:2
  3. 1:1
  4. 4:1

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Review Quantitative Chemistry questions for Chemistry, with correct answers shown and coverage across relative formula mass; moles and reacting masses; concentration calculations.

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