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NECO SSCE Stoichiometry of Chemical Reactions — practice questions — page 2

Explore 79 free Stoichiometry of Chemical Reactions questions in NECO SSCE Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Stoichiometry of Chemical Reactions questions and exercises with answers

Showing questions 31–60 of 79.

What is the net ionic equation for neutralizing any strong acid with an ionic hydroxide?Read the answer and worked solution →In terms of electrons, what happens to a species that is oxidized?Read the answer and worked solution →What happens to a species that is reduced?Read the answer and worked solution →How is the oxidation number of an element in a compound defined?Read the answer and worked solution →What is the oxidation number of an atom in an elemental substance such as O2, Na or Cl2?Read the answer and worked solution →What is the oxidation number of sulfur in H2S?Read the answer and worked solution →What is the oxidation number of sulfur in the sulfite ion, SO3 2-?Read the answer and worked solution →What is the oxidation number of sulfur in Na2SO4?Read the answer and worked solution →What is the oxidation number of nitrogen in KNO3?Read the answer and worked solution →What is the oxidation number of nitrogen in the ammonium ion, NH4+?Read the answer and worked solution →What is the oxidation number of aluminium in AlH3?Read the answer and worked solution →How is a combustion reaction described?Read the answer and worked solution →What happens in a single-displacement reaction?Read the answer and worked solution →Is ZnCO3(s) giving ZnO(s) and CO2(g) a redox reaction?Read the answer and worked solution →In C2H4(g) + 3O2(g) giving 2CO2(g) + 2H2O(l), what happens to carbon?Read the answer and worked solution →In the half-reaction method, what is added to balance the charge of a half-reaction?Read the answer and worked solution →Following the reporting convention, how are a 2+ charge and a plus two oxidation number written?Read the answer and worked solution →What does the stoichiometry of a reaction describe?Read the answer and worked solution →What is a stoichiometric factor?Read the answer and worked solution →A recipe uses 1 cup mix, three quarters of a cup of milk and one egg for eight pancakes. How many eggs give 24 pancakes?Read the answer and worked solution →For 2Al + 3I2 giving 2AlI3, how many moles of I2 react with 0.429 mol of Al?Read the answer and worked solution →For 3Ca(OH)2 + 2H3PO4 giving Ca3(PO4)2 + 6H2O, how many moles of Ca(OH)2 react with 1.36 mol of H3PO4?Read the answer and worked solution →For C3H8 + 5O2 giving 3CO2 + 4H2O, how many moles of CO2 form when 0.75 mol of propane burns?Read the answer and worked solution →For (NH4)2SO4 + Ca(OH)2 giving 2NH3 + CaSO4 + 2H2O, how many moles of NH3 come from 4.0 mol of Ca(OH)2?Read the answer and worked solution →Gallium metal of mass 29.0 g reacts as 4Ga + 3O2 giving 2Ga2O3. What mass of Ga2O3 can be prepared?Read the answer and worked solution →What mass of CO reacts with 25.13 g of Fe2O3 according to Fe2O3 + 3CO giving 2Fe + 3CO2?Read the answer and worked solution →What is a limiting reactant?Read the answer and worked solution →Combining 3 mol of H2 with 2 mol of Cl2 for H2 + Cl2 giving 2HCl, which reactant limits the product?Read the answer and worked solution →How do theoretical yield and actual yield differ?Read the answer and worked solution →How is the percent yield of a reaction calculated?Read the answer and worked solution →

Worked practice questions

What is the net ionic equation for neutralizing any strong acid with an ionic hydroxide?

  1. H3O+ and OH- give 2H2O
  2. H2O and OH- give H3O+
  3. H3O+ and H2O give 2OH-
  4. OH- and OH- give H2O and O2
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Correct answer: A. H3O+ and OH- give 2H2O

1. A strong acid in water is present as hydronium ions plus its anion. 2. An ionic hydroxide in water is present as its cation plus hydroxide ions. 3. The acid anion and the metal cation pass through unchanged, so both are spectator ions. 4. Removing them leaves only hydronium reacting with hydroxide. 5. Each H3O+ gives up one H+ to an OH-, and the two together yield 2 H2O. 6. So the net ionic equation is H3O+ plus OH- giving 2H2O. 7. The reverse forms in the other options would need water to split apart, which is not what happens here. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_

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In terms of electrons, what happens to a species that is oxidized?

  1. It gains electrons from another species
  2. It shares electrons with another species
  3. It loses electrons to another species
  4. It keeps its electrons entirely unchanged
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Correct answer: C. It loses electrons to another species

1. When sodium meets chlorine, the half-reactions show Na atoms losing electrons. 2. Loss of electrons is oxidation, so sodium is oxidized. 3. Chlorine atoms gain those electrons, which is reduction. 4. The two processes always happen together, since electrons lost by one species are gained by another. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_

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What happens to a species that is reduced?

  1. Its oxidation number rises by losing electrons
  2. Its oxidation number falls by gaining electrons
  3. Its oxidation number stays fixed throughout
  4. Its oxidation number falls by losing electrons
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Correct answer: B. Its oxidation number falls by gaining electrons

1. Reduction is the gain of electrons by a species. 2. Adding negative charge pulls the oxidation number down. 3. Chlorine going from 0 in Cl2 to -1 in NaCl is a clear case. 4. A rise in oxidation number by loss of electrons is oxidation, the opposite change. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_

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