Formulae and Equations questions

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Formulae and Equations question collection

Review Formulae and Equations questions for Chemistry, with correct answers shown and coverage across what does conservation of mass state for a closed chemical reaction; explaining why are chemical equations balanced; choosing which is the balanced equation for forming water.

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Question 1

What does conservation of mass state for a closed chemical reaction?
  1. Total reactant mass equals total product mass
  2. Product mass falls as energy is released
  3. Product mass rises as new substances form
  4. Only solid mass is conserved

Question 2

Why are chemical equations balanced?
  1. To conserve each type of atom
  2. To give both sides the same formula
  3. To make every coefficient equal
  4. To show the reaction is reversible

Question 3

Which is the balanced equation for forming water?
  1. \(2\mathrm{H}_{2} + \mathrm{O}_{2} \to 2\mathrm{H}_{2}\mathrm{O}\)
  2. \(\mathrm{H}_{2} + \mathrm{O}_{2} \to \mathrm{H}_{2}\mathrm{O}\)
  3. \(\mathrm{H}_{2} + \mathrm{O}_{2} \to 2\mathrm{H}_{2}\mathrm{O}\)
  4. \(2\mathrm{H}_{2} + 2\mathrm{O}_{2} \to 2\mathrm{H}_{2}\mathrm{O}\)

Question 4

How many oxygen atoms are in one formula unit of CaCO3?
  1. 3
  2. 1
  3. 2
  4. 4

Question 5

How many hydrogen atoms are in one molecule of H2SO4?
  1. 2
  2. 1
  3. 4
  4. 6

Question 6

How many atoms are in one H2SO4 molecule?
  1. 7
  2. 4
  3. 6
  4. 8

Question 7

Which formula has two hydrogen atoms for every oxygen atom?
  1. H2O
  2. HO2
  3. H2O2
  4. H3O

Question 8

If \(5\,\mathrm{g}\) of A reacts with \(7\,\mathrm{g}\) of B and all reactants are used, what mass of product forms?
  1. \(12\,\mathrm{g}\)
  2. \(2\,\mathrm{g}\)
  3. \(7\,\mathrm{g}\)
  4. \(35\,\mathrm{g}\)

Question 9

Carbon burns in oxygen to form carbon dioxide. If \(12\,\mathrm{g}\) of carbon forms \(44\,\mathrm{g}\) of CO2, what mass of oxygen reacted?
  1. \(32\,\mathrm{g}\)
  2. \(12\,\mathrm{g}\)
  3. \(44\,\mathrm{g}\)
  4. \(56\,\mathrm{g}\)

Question 10

In 2Mg + O2 → 2MgO, what does the 2 before Mg show?
  1. Two magnesium atoms react
  2. Magnesium has atomic number 2
  3. Each magnesium atom has 2 neutrons
  4. Two oxygen atoms are inside Mg

Question 11

What does the subscript 2 in H₂ mean?
  1. Two hydrogen atoms per molecule
  2. Two hydrogen molecules
  3. A charge of 2+
  4. Atomic number 2

Question 12

Why can measured mass fall during a reaction in an open flask?
  1. A gaseous product escapes
  2. A gaseous reactant enters
  3. The products absorb surrounding air
  4. The balance measures products differently

Question 13

Which setup best tests mass conservation when a reaction makes gas?
  1. A sealed container on a balance
  2. An open beaker on a balance
  3. A heated crucible without a lid
  4. A flask vented through an open tube

Question 14

What does the arrow in a chemical equation mean?
  1. Reacts to form
  2. Is mixed with
  3. Is equal to
  4. Is dissolved in

Question 15

How many oxygen atoms are shown by 3CO2?
  1. 6
  2. 2
  3. 3
  4. 9

Question 16

Which word equation represents iron reacting with sulfur?
  1. iron + sulfur → iron sulfide
  2. iron sulfide → iron + sulfur
  3. iron + sulfur → iron sulfate
  4. iron + sulfur → sulfur dioxide

Question 17

\(250\,\mathrm{cm^3}\) is equal to how many \(\mathrm{dm^3}\)?
  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 18

Which formula contains the most atoms in one particle?
  1. CH4
  2. H2O
  3. CO2
  4. O2

Question 19

In \(\mathrm{N}_2 + 3\mathrm{H}_2 \to 2\mathrm{NH}_3\), how many hydrogen molecules react with one nitrogen molecule?
  1. 3
  2. 1
  3. 2
  4. 6

Question 20

If the mass of products in a closed system is \(18\,\mathrm{g}\), what must be true about the reactants?
  1. Their total mass was also \(18\,\mathrm{g}\)
  2. Their total mass was less than \(18\,\mathrm{g}\)
  3. Their total mass was more than \(18\,\mathrm{g}\)
  4. Their mass is unrelated to product mass

Question 21

A reaction uses 15 g of reactants and makes 9 g of one product. What is the other product's mass?
  1. 6 g
  2. 9 g
  3. 15 g
  4. 24 g

Question 22

What is a product in a chemical equation?
  1. A substance made by the reaction
  2. A starting substance
  3. A catalyst that remains unchanged
  4. A condition written above the arrow

Question 23

What does a chemical formula show?
  1. Its elements and their atom ratio
  2. The temperature of a reaction
  3. The colour of a chemical
  4. The mass of one sample

Question 24

A reaction uses \(0.25\,\mathrm{kg}\) of a reactant. What is this mass in grams?
  1. \(250\,\mathrm{g}\)
  2. \(25\,\mathrm{g}\)
  3. \(2.5\,\mathrm{g}\)
  4. \(2500\,\mathrm{g}\)

Question 25

Which equation for sodium reacting with chlorine is balanced?
  1. 2Na + Cl₂ → 2NaCl
  2. Na + Cl₂ → NaCl
  3. 2Na + Cl₂ → NaCl
  4. Na + Cl → NaCl₂

Question 26

How many different elements are present in NaOH?
  1. 3
  2. 1
  3. 2
  4. 4

Question 27

Why can a metal gain mass when heated in air?
  1. Oxygen atoms join the metal
  2. Metal atoms are created by heat
  3. Energy becomes extra metal
  4. The balance counts hot objects twice

Question 28

What is the formula of magnesium oxide?
  1. MgO
  2. Mg₂O
  3. MgO₂
  4. Mg₂O₂

Question 29

What is the formula of calcium chloride?
  1. CaCl₂
  2. CaCl
  3. Ca₂Cl
  4. Ca₂Cl₂

Question 30

What is a reactant in a chemical equation?
  1. A starting substance
  2. A substance made by the reaction
  3. A catalyst left unchanged
  4. A condition written above the arrow

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Review Formulae and Equations questions for Chemistry, with correct answers shown and coverage across what does conservation of mass state for a closed chemical reaction; explaining why are chemical equations balanced; choosing which is the balanced equation for forming water.

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