Worksheet: Oxidation States

In this worksheet, we will practice determining the oxidation state of an element in a compound from the Lewis diagram or molecular formulas.

Q1:

Which of the following statements is true?

  • AAtoms or ions of the same element in a compound must have the same oxidation state.
  • BOnly atoms in an element can have an oxidation state of 0.
  • CThe oxidation state and formal charge of an atom in a compound must have the same sign.
  • DThe sum of oxidation states in a compound must equal the charge of the compound.
  • EThe oxidation state of an atom in a compound must always be a whole number.

Q2:

Which of the following statements is false?

  • AThe compounds NaVO34, KBrO3, and NO2+ all contain atoms or ions in the +5 oxidation state.
  • BThe compounds AlSe23, PCl3, and NaClO2 all contain atoms or ions in the +3 oxidation state.
  • CThe compounds BaCl2, NaSO223, and NO all contain atoms or ions in the +2 oxidation state.
  • DThe compounds MnO2, HSO23, and ZrCl4 all contain atoms or ions in the +4 oxidation state.
  • EThe compounds NaO22, NHOH2, and LiH all contain atoms in the 1 oxidation state.

Q3:

When hydrogen peroxide reacts with iron(II) ions in acidic aqueous solution, water and iron(III) ions are produced.

Write a balanced net ionic equation for this reaction, including state symbols.

  • A 2 H O ( ) + 3 H ( ) + 3 F e 2 H O ( ) + 3 F e ( ) 2 2 + 2 + 2 3 + a q a q l a q
  • B H O ( ) + H ( ) + F e 2 H O ( ) + F e ( ) 2 2 + 2 + 2 3 + a q a q l a q
  • C H O ( ) + 2 H O ( ) + 2 F e 4 O H ( ) + 2 F e ( ) 2 2 2 2 + 3 + a q l a q a q
  • D H O ( ) + 2 H ( ) + 2 F e 2 H O ( ) + 2 F e ( ) 2 2 + 2 + 2 3 + a q a q l a q
  • E H O ( ) + 2 F e 2 O H ( ) + 2 F e ( ) 2 2 2 + 3 + a q a q a q

What is the change in the oxidation state of O in this reaction?

Which elements’ atoms or ions are reduced in this reaction?

  • A O only
  • B F e only
  • C H only
  • DBoth H and O
  • EBoth H and Fe

Q4:

When dichromate ions (CrO)272 react with iron(II) ions in an acidic aqueous solution, chromium(III) ions are produced.

Write a balanced net ionic equation for this reaction, including state symbols.

  • A C r O ( ) + 4 F e ( ) + 1 4 H ( ) 2 C r ( ) + 4 F e ( ) + 7 H O ( ) 2 7 2 2 + + 3 + 3 + 2 a q a q a q a q a q l
  • B C r O ( ) + 6 F e ( ) + 2 H O ( ) 2 C r ( ) + 3 F e O ( ) + 4 H ( ) 2 7 2 2 + 2 3 + 2 3 + a q a q l a q s a q
  • C C r O ( ) + 6 F e ( ) + 1 4 H ( ) 2 C r ( ) + 6 F e ( ) + 7 H O ( ) 2 7 2 2 + + 3 + 3 + 2 a q a q a q a q a q l
  • D C r O ( ) + 4 F e ( ) + 2 H ( ) 2 C r ( ) + 2 F e O ( ) + H O ( ) 2 7 2 2 + + 3 + 2 3 2 a q a q a q a q s l
  • E C r O ( ) + 6 F e ( ) + 7 H O ( ) 2 C r ( ) + 6 F e ( ) + 1 4 O H ( ) 2 7 2 2 + 2 3 + 3 + a q a q l a q a q a q

By how much does the oxidation state of Cr change in this reaction?

Which elements’ atoms or ions are reduced in this reaction?

  • A F e only
  • B O only
  • C C r only
  • DBoth Fe and O
  • EBoth Cr and O

Q5:

Tin reacts with hydrochloric acid to form aqueous tin(II) chloride.

Write a balanced molecular equation for this reaction, including state symbols.

  • A S n ( ) + 4 H C l ( ) S n C l ( ) + 2 H ( ) s a q a q g 4 2
  • B S n ( ) + 4 H C l ( ) S n C l ( ) + 2 H ( ) + C l ( ) s a q a q g g 2 2 2
  • C S n ( ) + 4 H C l ( ) S n C l ( ) + 4 H ( ) s a q a q a q 4 +
  • D S n ( ) + 2 H C l ( ) S n C l ( ) + 2 H ( ) s a q a q a q 2 +
  • E S n ( ) + 2 H C l ( ) S n C l ( ) + H ( ) s a q a q g 2 2

By how much does the oxidation state of Sn change in this reaction?

  • A + 1
  • B + 2
  • C + 3
  • D + 4
  • E0

Which term best describes the role of chloride ions in this reaction?

  • AOxidizing agent
  • BAcid
  • CReducing agent
  • DBase
  • ESpectator ion

Q6:

The complete combustion of ethene is an example of a reduction–oxidation reaction.

Write a balanced molecular equation for this reaction, including state symbols.

  • A C H ( ) + O ( ) 2 C ( ) + 2 H O ( ) 2 4 2 2 g g s g
  • B C H ( ) + 2 O ( ) 2 C O ( ) + 2 H O ( ) 2 4 2 2 g g g g
  • C C H ( ) + 3 O ( ) 2 C O ( ) + 2 H O ( ) 2 4 2 2 2 g g g g
  • D 2 C H ( ) + 5 O ( ) 2 C O ( ) + 2 C O ( ) + 4 H O ( ) 2 4 2 2 2 g g g g g
  • E 2 C H ( ) + 3 O ( ) 2 C ( ) + 2 C O ( ) + 4 H O ( ) 2 4 2 2 g g s g g

By how much does the oxidation state of C change in this reaction?

  • A0
  • B + 8
  • C 8
  • D + 4
  • E 4

Which atoms are oxidized in this reaction?

  • ABoth O and H
  • B H only
  • CBoth C and H
  • D C only
  • E O only

Q7:

Hydrogen peroxide decomposes to form gaseous oxygen.

Write a balanced molecular equation for this reaction, including state symbols.

  • A 2 H O ( ) 2 H O ( ) + O ( ) 2 2 2 2 a q l g
  • B H O ( ) H ( ) + O ( ) 2 2 2 2 a q g g
  • C 3 H O ( ) 2 H O ( ) + H ( ) + 2 O ( ) 2 2 2 2 2 a q l g g
  • D 2 H O ( ) 2 H ( ) + O ( ) 2 2 + 2 a q a q g
  • E 4 H O ( ) 2 H O ( ) + 4 O H ( ) + O ( ) 2 2 2 2 a q l a q g

What is the average change in the oxidation state of O in this reaction?

Q8:

Zinc oxide can be produced by the thermal decomposition of zinc carbonate.

Write a balanced molecular equation for this reaction, including state symbols.

  • A Z n C O ( ) Z n O ( ) + C O ( ) 3 2 s s g
  • B Z n C O ( ) Z n O ( ) + C ( ) + O ( ) 3 2 s s s g
  • C Z n C O ( ) Z n O ( ) + C O ( ) 3 2 s s g
  • D 2 Z n C O ( ) 2 Z n O ( ) + 2 C O ( ) + O ( ) 3 2 s s g g
  • E 2 Z n C O ( ) 2 Z n O ( ) + 2 C ( ) + O ( ) 3 2 2 s s s g

By how much does the oxidation state of Zn change in this reaction?

Q9:

Solid aluminum reacts with solid ammonium perchlorate (NHClO44) to form aluminum oxide, aluminum chloride, steam, and nitrogen.

Write a balanced molecular equation for this reaction, including state symbols.

  • A 5 A l ( ) + 9 N H C l O ( ) A l O ( ) + 3 A l C l ( ) + 1 8 H O ( ) + 4 N ( ) s s s s g g 4 4 2 3 3 2 2
  • B 4 A l ( ) + 6 N H C l O ( ) 2 A l O ( ) + 2 A l C l ( ) + 1 8 H O ( ) + 3 N ( ) s s s s g g 4 4 2 3 3 2 2
  • C 6 A l ( ) + 6 N H C l O ( ) 2 A l O ( ) + 2 A l C l ( ) + 1 8 H O ( ) + 3 N ( ) s s s s g g 4 4 2 3 3 2 2
  • D 9 A l ( ) + 9 N H C l O ( ) 3 A l O ( ) + 3 A l C l ( ) + 2 7 H O ( ) + 5 N ( ) s s s s g g 4 4 2 3 3 2 2
  • E 1 0 A l ( ) + 6 N H C l O ( ) 4 A l O ( ) + 2 A l C l ( ) + 1 2 H O ( ) + 3 N ( ) s s s s g g 4 4 2 3 3 2 2

By how much does the oxidation state of Cl change in this reaction?

Which atom is oxidized in this reaction?

  • A N
  • B H
  • C A l
  • D C l
  • E O

Q10:

Hypobromous acid (BrOH) reacts under acidic aqueous conditions to form bromide ions and oxygen.

Write a balanced ionic equation for this reaction, including state symbols.

  • A 2 B r O H ( ) 2 B r ( ) + O ( ) + H ( ) a q a q g g 2 2
  • B 2 B r O H ( ) + 2 H ( ) 2 B r ( ) + O ( ) + 2 H ( ) a q a q a q g g + 2 2
  • C 2 B r O H ( ) 2 B r ( ) + O ( ) + 2 H ( ) a q a q g a q 2 +
  • D B r O H ( ) + H O ( ) B r ( ) + O ( ) + 3 H ( ) a q l a q g a q 2 2 +
  • E 4 B r O H ( ) 4 B r ( ) + O ( ) + 2 H O ( ) a q a q g l 2 2

What is the change in the oxidation state of Br in this reaction?

Q11:

Barium carbonate reacts with aqueous butanoic acid to form aqueous barium butanoate.

Write a balanced molecular equation for this reaction, including state symbols.

  • A B a C O ( ) + C H C O O H ( ) B a ( C H C O O ) ( ) + H O ( ) + C O ( ) 3 3 7 3 7 2 2 s a q a q l g
  • B B a C O ( ) + 2 C H C O O H ( ) B a ( C H C O O ) ( ) + H O ( ) + C O ( ) 3 3 7 3 7 2 2 2 s a q a q l g
  • C B a C O ( ) + 2 C H C O O H ( ) B a ( C H C O O ) ( ) + H O ( ) + C O ( ) 3 3 7 3 7 2 2 2 s a q s l g
  • D B a C O ( ) + 2 C H C O O H ( ) B a ( C H C O O ) ( ) + H O ( ) + C O ( ) 3 2 5 2 5 2 2 2 a q a q a q l g
  • E B a C O ( ) + C H C O O H ( ) B a ( C H C O O ) ( ) + H O ( ) + C O ( ) 3 2 5 2 5 2 2 a q a q a q l g

By how much does the oxidation state of Ba change in this reaction?

Which term best describes the role of butanoic acid in this reaction?

  • AOxidizing agent
  • BSpectator species
  • CLewis acid
  • DReducing agent
  • EBrønsted–Lowry acid

Q12:

Hydrogen sulfide can be removed from natural gas by reaction with aqueous sodium carbonate.

Write a balanced net ionic equation for this reaction, including state symbols.

  • A H S ( ) + 2 N a ( ) + C O ( ) 2 N a ( ) + S ( ) + H O ( ) + C O ( ) 2 + 3 2 + 2 2 2 g a q a q a q a q l g
  • B H S ( ) + N a C O ( ) N a S ( ) + H O ( ) + C O ( ) 2 2 3 2 2 2 g a q a q l g
  • C H S ( ) + N a C O ( ) N a S ( ) + H O ( ) + C O ( ) 2 2 3 2 2 2 g s s l g
  • D H S ( ) + C O ( ) S ( ) + H O ( ) + C O ( ) 2 3 2 2 2 2 g a q a q l g
  • E H S ( ) + C O ( ) S ( ) + H O ( ) + C O ( ) 2 3 2 2 2 2 l a q a q l g

By how much does the oxidation state of C change in this reaction?

Which term best describes the role of carbonate ions in this reaction?

  • ABrønsted–Lowry acid
  • BLewis base
  • COxidizing agent
  • DLewis acid
  • EBrønsted–Lowry base

Q13:

What is the oxidation state of P in phosphoric acid?

  • A + 5
  • B + 4
  • C + 3
  • D + 2
  • E + 6

Q14:

Hydrogen sulfide can be removed from natural gas by reaction with solid calcium hydroxide.

Write a balanced molecular equation for this reaction, including state symbols.

  • A H S ( ) + C a ( O H ) ( ) C a S ( ) + 2 H O ( ) 2 2 2 g s s l
  • B H S ( ) + C a ( O H ) ( ) C a S ( ) + H O ( ) 2 2 2 g s s l
  • C H S ( ) + C a O H ( ) C a S ( ) + H O ( ) g s s l 2
  • D 2 H S ( ) + C a ( O H ) ( ) C a S ( ) + 2 H O ( ) g s s l 2 2 2
  • E H S ( ) + 2 C a O H ( ) C a S ( ) + 2 H O ( ) 2 2 2 g s s l

By how much does the oxidation state of S change in this reaction?

Which term best describes the role of hydrogen sulfide in this reaction?

  • ALewis acid
  • BReducing agent
  • CBrønsted–Lowry base
  • DBrønsted–Lowry acid
  • ELewis base

Q15:

Sodium bromide reacts with chlorine in aqueous solution.

Write a balanced net ionic equation for this reaction, including state symbols.

  • A 2 B r ( ) + C l ( ) 2 C l ( ) + B r ( ) 2 2 a q a q a q l
  • B 2 N a B r ( ) + C l ( ) 2 N a C l ( ) + B r ( ) a q a q a q a q 2 2
  • C 2 N a ( ) + 2 B r ( ) + C l ( ) 2 N a C l ( ) + B r ( ) + 2 2 a q a q a q s a q
  • D 2 N a B r ( ) + C l ( ) 2 N a C l ( ) + B r ( ) a q a q s l 2 2
  • E 2 B r ( ) + C l ( ) 2 C l ( ) + B r ( ) 2 2 a q a q a q a q

By how much does the oxidation state of Br change in this reaction?

  • A 1
  • B0
  • C 2
  • D+1
  • E+2

Which term best describes the role of chlorine in this reaction?

  • ALewis base
  • BReducing agent
  • CLewis acid
  • DOxidizing agent
  • ESpectator species

Q16:

Hydrogen and fluorine react when irradiated with intense light.

Write a balanced molecular equation for this reaction, including state symbols.

  • A H ( ) + F ( ) H F ( ) + a q a q l
  • B H ( ) + F ( ) H F ( ) + a q a q a q
  • C H ( ) + F ( ) H F ( ) g g g
  • D H ( ) + F ( ) 2 H F ( ) 2 2 g g l
  • E H ( ) + F ( ) 2 H F ( ) 2 2 g g g

By how much does the oxidation state of F change in this reaction?

Which term best describes the role of fluorine in this reaction?

  • ABrønsted–Lowry base
  • BSpectator species
  • CLewis base
  • DReducing agent
  • EOxidizing agent

Q17:

Solid strontium oxide reacts with liquid sulfuric acid to form solid strontium sulfate.

Write a balanced molecular equation for this reaction, including state symbols.

  • A S r O ( ) + H S O ( ) S r S O ( ) + H O ( ) s l a q l 2 4 4 2
  • B S r O ( ) + 2 H S O ( ) S r ( S O ) ( ) + H O ( ) 2 2 4 4 2 2 s l s l
  • C S r O ( ) + H S O ( ) S r S O ( ) + H O ( ) 2 2 4 2 4 2 s l a q l
  • D S r O ( ) + H S O ( ) S r S O ( ) + H O ( ) 2 2 4 2 4 2 s l s l
  • E S r O ( ) + H S O ( ) S r S O ( ) + H O ( ) s l s l 2 4 4 2

By how much does the oxidation state of Sr change in this reaction?

Which term best describes the role of strontium oxide in this reaction?

  • ALewis acid
  • BOxidizing agent
  • CLewis base
  • DBrønsted–Lowry acid
  • EBrønsted–Lowry base

Q18:

Aqueous carbon dioxide reacts with limewater to form solid calcium carbonate.

Write a balanced net ionic equation for this reaction, including state symbols.

  • A C O ( ) + C a ( ) + 2 O H ( ) C a C O ( ) + H O ( ) 2 2 + 3 2 g a q a q s l
  • B C O ( ) + C a ( O H ) ( ) C a C O ( ) + H O ( ) 2 2 3 2 g a q s l
  • C C O ( ) + C a ( ) + 2 O H ( ) C a ( ) + C O ( ) + H O ( ) 2 2 + 2 + 3 2 2 g a q a q s s l
  • D C O ( ) + 2 O H ( ) C O ( ) + H O ( ) 2 3 2 2 g a q s l
  • E C O ( ) + 2 O H ( ) C O ( ) + H O ( ) 2 3 2 2 g a q a q l

By how much does the oxidation state of C change in this reaction?

Which term best describes the role of hydroxide ions in this reaction?

  • ASpectator ion
  • BBrønsted–Lowry base
  • CBrønsted–Lowry acid
  • DLewis acid
  • ELewis base

Q19:

Gaseous sulfur trioxide reacts with water to form sulfuric acid.

Write a balanced molecular equation for this reaction, including state symbols.

  • A 2 S O ( ) + 2 H O ( ) 2 H S O ( ) + O ( ) 3 2 2 4 2 g l a q g
  • B 3 S O ( ) + 2 H O ( ) 2 H S O ( ) 2 2 2 3 g l a q
  • C 3 S O ( ) + 2 H O ( ) 3 H S O ( ) 3 2 2 4 g l a q
  • D S O ( ) + 2 H O ( ) H S O ( ) 2 2 2 3 g l a q
  • E S O ( ) + H O ( ) H S O ( ) 3 2 2 4 g l a q

By how much does the oxidation state of S change in this reaction?

Which term best describes the role of sulfur trioxide in this reaction?

  • ALewis acid
  • BBrønsted–Lowry base
  • CBrønsted–Lowry acid
  • DReducing agent
  • ELewis base

Q20:

Solid calcium reacts with water to form aqueous calcium hydroxide.

Write a balanced molecular equation for this reaction, including state symbols.

  • A C a ( ) + 2 H O ( ) C a ( O H ) ( ) + H ( ) s l a q g 2 2 2
  • B C a ( ) + H O ( ) C a ( O H ) ( ) s l a q 2 2
  • C 2 C a ( ) + 2 H O ( ) 2 C a O H ( ) + H ( ) s l a q g 2 2
  • D C a ( ) + H O ( ) C a O H ( ) + H ( ) s l a q a q 2 +
  • E C a ( ) + 2 H O ( ) C a ( O H ) ( ) + 2 H ( ) s l a q a q 2 2 +

By how much, on average, does the oxidation state of H change in this reaction?

Which term best describes the role of water in this reaction?

  • AOxidizing agent
  • BSpectator species
  • CAcid
  • DReducing agent
  • EBase

Q21:

Chloric(VII) acid can be neutralized by the addition of solid magnesium hydroxide.

Write a balanced molecular equation for this reaction, including state symbols.

  • A 4 M g ( O H ) ( ) + 4 H C l O ( ) 4 M g O ( ) + 2 C l ( ) + 7 O ( ) + 6 H O ( ) 2 4 2 2 2 s a q s g g l
  • B M g ( O H ) ( ) + H C l O ( ) M g O ( ) + H C l O ( ) + H O ( ) + O ( ) 2 4 2 2 2 s a q s a q l g
  • C 4 M g ( O H ) ( ) + 2 H C l O ( ) M g ( C l O ) ( ) + 3 M g O ( ) + 5 H O ( ) 2 4 4 2 2 s a q a q s l
  • D M g ( O H ) ( ) + H C l O ( ) M g O ( ) + H C l O ( ) + H O ( ) 2 4 4 2 s a q s a q l
  • E M g ( O H ) ( ) + 2 H C l O ( ) M g ( C l O ) ( ) + 2 H O ( ) 2 4 4 2 2 s a q a q l

By how much does the oxidation state of Cl change in this reaction?

Which term best describes the role of chlorate(VII) ions in this reaction?

  • AAcid
  • BReducing agent
  • COxidizing agent
  • DSpectator ion
  • EBase

Q22:

Solid phosphorous (P)4 reacts with oxygen to form solid phosphorus pentoxide.

Write a balanced molecular equation for this reaction, including state symbols.

  • A P ( ) + 4 O ( ) 4 P O ( ) 4 2 2 s g s
  • B P ( ) + 5 O ( ) P O ( ) 4 2 4 1 0 s g s
  • C P ( ) + 1 0 O ( ) 4 P O ( ) 4 2 5 s g s
  • D P ( ) + 5 O ( ) 2 P O ( ) 4 2 2 5 s g s
  • E P ( ) + 1 0 O ( ) 2 P O ( ) 4 2 2 1 0 s g s

By how much does the oxidation state of P change in this reaction?

  • A 4
  • B 5
  • C + 1 0
  • D + 5
  • E + 4

Which term best describes the role of phosphorus in this reaction?

  • AAcid
  • BOxidizing agent
  • CReducing agent
  • DBase
  • ESpectator species

Q23:

Solid aluminum reacts with aqueous copper(II) bromide to form solid copper.

Write a balanced net ionic equation for this reaction, including state symbols.

  • A A l ( ) + 2 C u B r ( ) A l B r ( ) + 2 C u ( ) s a q a q s 2 3
  • B A l ( ) + 3 C u ( ) A l ( ) + 3 C u ( ) s a q a q s + 3 +
  • C A l ( ) + C u ( ) A l ( ) + C u ( ) s a q a q s 2 + 3 +
  • D 2 A l ( ) + 3 C u ( ) 2 A l ( ) + 3 C u ( ) s a q a q s 2 + 3 +
  • E A l ( ) + 3 C u B r ( ) A l B r ( ) + 3 C u ( ) s a q a q s 3

By how much does the oxidation state of Br change in this reaction?

Which term best describes the role of copper(II) ions in this reaction?

  • ABase
  • BSpectator ion
  • COxidizing agent
  • DAcid
  • EReducing agent

Q24:

Solid aluminum reacts with fluorine gas to form solid aluminum fluoride.

Write a balanced molecular equation for this reaction, including state symbols.

  • A A l ( ) + 2 F ( ) A l F ( ) s g s 2 4
  • B 2 A l ( ) + 3 F ( ) 2 A l F ( ) s g s 2 3
  • C 2 A l ( ) + 3 F ( ) A l F ( ) s g s 3
  • D A l ( ) + 2 F ( ) A l F ( ) s g s 2 4
  • E A l ( ) + 4 F ( ) A l F ( ) s g s 4

By how much does the oxidation state of Al change in this reaction?

  • A + 4
  • B + 2
  • C + 3
  • D0
  • E + 1

Which term best describes the role of aluminum in this reaction?

  • AOxidizing agent
  • BAcid
  • CSpectator ion
  • DBase
  • EReducing agent

Q25:

Hydrochloric acid reacts with aqueous strontium hydroxide to produce aqueous strontium chloride.

Write a balanced net ionic equation for this reaction, including state symbols.

  • A O H ( ) + H ( ) H O ( ) + 2 a q a q l
  • B O H ( ) + H C l ( ) C l ( ) + H O ( ) 2 a q a q a q l
  • C S r ( O H ) ( ) + 2 H C l ( ) S r C l ( ) + 2 H O ( ) 2 2 2 a q a q a q l
  • D S r ( ) + 2 C l ( ) S r C l ( ) 2 + 2 a q a q a q
  • E S r ( O H ) ( ) + 2 H ( ) S r ( ) + 2 H O ( ) 2 + 2 + 2 a q a q a q l

By how much does the oxidation state of H change in this reaction?

Which term best describes the role of strontium in this reaction?

  • ASpectator ion
  • BAcid
  • CBase
  • DOxidizing agent
  • EReducing agent

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