Worksheet: Balancing Equations

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In this worksheet, we will practice determining the stoichiometry of a reaction equation by balancing the numbers of atoms in the reactants and products.

Q1:

Which element is out of balance in the chemical equation CHCHOH+O2CO+3HO32222?

  • AOxygen
  • BHydrogen
  • CCarbon

Q2:

How many more oxygen molecules are required to balance the chemical equation CHCHOH+O2CO+3HO32222?

Q3:

The Marsh test is a method used historically for the detection of arsenic, a toxic element, in mixed materials. The sample is burned to convert any arsenic present to arsenic(III) trioxide (AsO)23 and then treated with nitric acid (HNO)3 and metallic zinc. If arsenic is present, a garlic smell is detected due to the production of arsine gas (AsH)3. The equation for this reaction is as follows: AsO+Zn+HNOAsH+6Zn(NO)+HO2333322𝑎𝑏𝑐𝑑.

The coefficients 𝑎, 𝑏, 𝑐, and 𝑑 are all whole numbers.

Find the value of 𝑎.

Find the value of 𝑏.

Find the value of 𝑐.

Find the value of 𝑑.

Q4:

The reaction of selenium, selenium tetrachloride (SeCl)4, and aluminum trichloride (AlCl)3 produces a compound with the molecular formula SeAlCl, according to the following equation: 15Se+SeCl+4AlCl2SeAlCl43.

Find the value of 𝑥.

Find the value of 𝑦.

Find the value of 𝑧.

Q5:

Complete combustion reactions are described by the following equation: X+OCO+HO𝑎𝑏𝑐.222

In this equation, 𝑎,𝑏, and 𝑐 are whole numbers or simple fractions. The compound X is a single molecule of an organic fuel. Possible organic fuels include butanol (CHO)410, catechol (CHO)662, and cyclopentene (CH)58.

Place the listed organic fuels in order of increasing values of 𝑎.

  • AButanol, catechol, cyclopentene
  • BCatechol, butanol, cyclopentene
  • CCyclopentene, catechol, butanol
  • DCyclopentene, butanol, catechol
  • EButanol, cyclopentene, catechol

Place the listed organic fuels in order of increasing values of 𝑏.

  • ACatechol, butanol, cyclopentene
  • BButanol, cyclopentene, catechol
  • CCyclopentene, catechol, butanol
  • DCyclopentene, butanol, catechol
  • ECatechol, cyclopentene, butanol

Place the listed organic fuels in order of increasing values of 𝑐.

  • AButanol, cyclopentene, catechol
  • BCatechol, butanol, cyclopentene
  • CCyclopentene, butanol, catechol
  • DButanol, catechol, cyclopentene
  • ECatechol, cyclopentene, butanol

Q6:

Sodium azide (NaN)3 reacts with nitrous acid (HNO)2 to produce nitric oxide (NO), sodium hydroxide (NaOH), and nitrogen gas. This reaction is described by the following equation: NaN+HNON+NO+NaOH322𝑤𝑥𝑦𝑧.

The coefficients 𝑤, 𝑥, 𝑦, and 𝑧 are whole numbers or simple fractions.

In which order are the coefficients 𝑤, 𝑥, 𝑦, and 𝑧 most easily determined?

  • A 𝑤 , 𝑦 , 𝑧 , 𝑥
  • B 𝑥 , 𝑤 , 𝑦 , 𝑧
  • C 𝑧 , 𝑦 , 𝑥 , 𝑤
  • D 𝑤 , 𝑧 , 𝑥 , 𝑦
  • E 𝑧 , 𝑤 , 𝑦 , 𝑥

When the coefficient of NaN3 is set to a value of 1, as shown, which coefficients are also equal to 1?

  • A 𝑥 , 𝑦 , 𝑧
  • B 𝑥 , 𝑦
  • C 𝑤 , 𝑥 , 𝑦 , 𝑧
  • D 𝑤 , 𝑦 , 𝑧
  • E 𝑤 , 𝑥

Q7:

The black mineral magnetite (FeO)34 reacts with high-temperature oxygen to form red-brown ferric oxide (FeO)23. This reaction is described by the following equation. 𝑥𝑦𝑧FeO+OFeO34223

The coefficients 𝑥, 𝑦, and 𝑧 are whole numbers and may be determined by balancing the numbers of Fe and O atoms on the two sides of the equation.

When balancing the equation, which of the two elements should be considered first, and why?

  • A F e , because fewer reactants and products contain atoms or ions of this element
  • B F e , because fewer atoms of this element appear in the equation
  • C O , because all reactants and products contain atoms or ions of this element
  • D O , because more atoms of this element appear in the equation
  • E O , because it appears in the equation as a pure element

What are the smallest possible whole-number values of 𝑥, 𝑦, and 𝑧?

  • A 𝑥 = 2 , 𝑦 = 2 , 𝑧 = 3
  • B 𝑥 = 3 , 𝑦 = 1 , 𝑧 = 4
  • C 𝑥 = 4 , 𝑦 = 1 , 𝑧 = 6
  • D 𝑥 = 1 , 𝑦 = 1 , 𝑧 = 2
  • E 𝑥 = 3 , 𝑦 = 2 , 𝑧 = 6

Q8:

Iron(III) sulfide (FeS)23 reacts with oxygen to produce iron(III) oxide (FeO)23 and sulfur dioxide (SO)2. Write a balanced chemical equation for this reaction, using the smallest possible whole-number coefficients for the reactants and products.

  • A 2 F e S + 5 O 2 F e O + 2 S O 2 3 2 2 3 2
  • B F e S + 5 O F e O + 3 S O 2 3 2 2 3 2
  • C F e S + 3 O F e O + 3 S O 2 3 2 2 3 2
  • D 2 F e S + 9 O 2 F e O + 6 S O 2 3 2 2 3 2
  • E 3 F e S + 9 O 3 F e O + 5 S O 2 3 2 2 3 2

Q9:

Antimony(III) oxide (SbO)23 is a white solid used as a flame retardant additive in some plastics. The compound may be produced by the oxidation of antimony(III) sulfide (SbS)23 in a high-temperature furnace. The equation for this reaction is as follows: 𝑥𝑦𝑧.SbS+O2SbO+SO232232

The coefficients 𝑥, 𝑦, and 𝑧 are whole numbers and may be determined by balancing the numbers of O, S, and Sb atoms on the two sides of the equation.

In which order are the coefficients 𝑥, 𝑦, and 𝑧 most easily determined?

  • A 𝑧 , 𝑥 , 𝑦
  • B 𝑦 , 𝑥 , 𝑧
  • C 𝑥 , 𝑦 , 𝑧
  • D 𝑥 , 𝑧 , 𝑦
  • E 𝑦 , 𝑧 , 𝑥

What are the values of 𝑥, 𝑦, and 𝑧?

  • A 𝑥 = 2 , 𝑦 = 6 , 𝑧 = 3
  • B 𝑥 = 3 , 𝑦 = 3 , 𝑧 = 6
  • C 𝑥 = 2 , 𝑦 = 9 , 𝑧 = 6
  • D 𝑥 = 2 , 𝑦 = 3 , 𝑧 = 3
  • E 𝑥 = 3 , 𝑦 = 9 , 𝑧 = 3

Q10:

Heating barium fluorosulfonate (Ba(SOF))32 produces barium sulfate (BaSO)4 and another compound X, according to the following equation: Ba(SOF)BaSO+X324. What is the molecular formula of compound X?

  • A S O F 2
  • B O F 2
  • C S O F 2 2
  • D S O F 2 2
  • E O F 2

Q11:

The reaction of nitric acid (HNO)3 with copper(I) oxide (CuO)2 produces copper nitrate (Cu(NO))32, nitric oxide (NO), and water. Which of the following is a balanced chemical equation for this reaction?

  • A 8 H N O + C u O 4 C u ( N O ) + N O + 4 H O 3 2 3 2 2
  • B 5 H N O + C u O 2 C u ( N O ) + N O + 5 H O 3 2 3 2 2
  • C 1 4 H N O + 3 C u O 6 C u ( N O ) + 2 N O + 7 H O 3 2 3 2 2
  • D 1 5 H N O + 3 C u O 6 C u ( N O ) + 3 N O + 8 H O 3 2 3 2 2
  • E 1 6 H N O + 3 C u O 6 C u ( N O ) + 4 N O + 8 H O 3 2 3 2 2

Q12:

Iodic acid (HIO)3 can be produced by the reaction of iodine (I)2 and chlorine (Cl)2 with water. Which of the following is a balanced chemical equation for this reaction?

  • A 3 I + 4 C l + 7 H O 6 H I O + 8 H C l 2 2 2 3
  • B 2 I + 5 C l + 1 2 H O 4 H I O + 1 0 H C l 2 2 2 3
  • C 2 I + 3 C l + 5 H O 4 H I O + 6 H C l 2 2 2 3
  • D I + 3 C l + 4 H O 2 H I O + 6 H C l 2 2 2 3
  • E I + 5 C l + 6 H O 2 H I O + 1 0 H C l 2 2 2 3

Q13:

Nitric oxide (NO) reacts with oxygen and water to produce nitrous acid (HNO)2 as the only product. How many molecules of nitric oxide react with each oxygen molecule in this reaction?

Q14:

The dark green solid molybdenum(V) chloride (MoCl)5 reacts with metallic gray molybdenum to produce orange crystals of molybdenum(II) chloride (MoCl)612, according to the following equation: 𝑥𝑦.MoCl+Mo5MoCl5612 The coefficients 𝑥 and 𝑦 are both whole numbers.

Find the value of 𝑥.

Find the value of 𝑦.

Q15:

A compound with molecular formula NaVOH is produced according to the following equation: 5NaVO+12HCl2NaVOH+4HO+12NaCl44122.

Find the value of 𝑎.

Find the value of 𝑏.

Find the value of 𝑐.

Find the value of 𝑑.

Q16:

Aluminum metal and bromine (Br)2 react to form aluminum bromide (AlBr)3.

Write a balanced chemical equation for this reaction using the smallest possible whole number coefficients for the reactants and products.

  • A 3 A l + 3 B r 2 A l B r 2 3
  • B A l + B r A l B r 2 3
  • C 2 A l + B r 2 A l B r 2 3
  • D A l + 2 B r A l B r 2 3
  • E 2 A l + 3 B r 2 A l B r 2 3

Expressed as a whole number or simple fraction, how many aluminum bromide molecules are produced for every 6 bromine molecules?

Expressed as a whole number or simple fraction, how many bromine molecules react for every 3 atoms of aluminum?

  • A 9 2
  • B 3 2
  • C2
  • D3
  • E6

Expressed as a whole number or simple fraction, how many aluminum atoms react for every 1 molecule of bromine?

  • A3
  • B 3 2
  • C 2 3
  • D2
  • E6

Q17:

The complete combustion of pentene is described by the following equation: CH+OCO+HO510222𝑥𝑦𝑧. This equation is balanced by adjusting the values of 𝑥, 𝑦, and 𝑧 such that there are equal numbers of C, H, and O atoms on the two sides of the equation.

Which of the following is the most sensible order in which we can balance the values of 𝑥, 𝑦, and 𝑧?

  • A 𝑧 , 𝑥 , 𝑦
  • B 𝑥 , 𝑦 , 𝑧
  • C 𝑥 , 𝑧 , 𝑦
  • D 𝑦 , 𝑥 , 𝑧
  • E 𝑦 , 𝑧 , 𝑥

Calculate the values of 𝑥, 𝑦, and 𝑧.

  • A 𝑥 = 7 . 5 , 𝑦 = 2 . 5 , 𝑧 = 1 0
  • B 𝑥 = 7 . 5 , 𝑦 = 5 , 𝑧 = 5
  • C 𝑥 = 5 , 𝑦 = 5 , 𝑧 = 1 0
  • D 𝑥 = 1 5 , 𝑦 = 7 . 5 , 𝑧 = 1 5
  • E 𝑥 = 5 , 𝑦 = 2 . 5 , 𝑧 = 5

Q18:

Reaction of ammonia (NH)3 with oxygen produces nitric oxide (NO) and water as the only products. Write a balanced chemical equation for this reaction using the smallest possible whole number coefficients for the reactants and products.

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

Q19:

An organic compound has the molecular formula CHO, where 𝑥, 𝑦, and 𝑧 are whole numbers. The complete combustion of this compound is described by the following equation: 2CHO+15O10CO+12HO222.

Find the value of 𝑥.

Find the value of 𝑦.

Find the value of 𝑧.

Q20:

When heated, phosphorous acid (HPO)33 decomposes into phosphoric acid (HPO)34 and the pungent toxic gas phosphine (PH)3. Write a balanced chemical equation for this reaction using the smallest possible whole number coefficients for the reactants and products.

  • A 3 H P O 2 H P O + P H 3 3 3 4 3
  • B 5 H P O 3 H P O + 2 P H 3 3 3 4 3
  • C 4 H P O 2 H P O + 2 P H 3 3 3 4 3
  • D 4 H P O 3 H P O + P H 3 3 3 4 3
  • E 2 H P O H P O + P H 3 3 3 4 3

Q21:

Heating a mixture of the vanadium oxides VO25 and VO23 produces another solid vanadium oxide. The equation for this reaction is as follows: VO+VOVO25232𝑎. In this equation, the coefficient 𝑎 and subscript 𝑏 are both whole numbers.

Find the value of 𝑎.

Find the value of 𝑏.

Q22:

An acid-base reaction is described by the following equation: HSO+2NaOHNaSO+HO24242𝑥.

Find the value of the coefficient 𝑥.

Q23:

Hydrogen iodide is produced by the reaction of hydrogen and iodine, according to the shown equation: 𝑥𝑦𝑧.H+IHI22

The coefficients 𝑥, 𝑦, and 𝑧 are whole numbers. What are the smallest possible values of 𝑥, 𝑦, and 𝑧?

  • A 𝑥 = 1 , 𝑦 = 1 , 𝑧 = 1
  • B 𝑥 = 1 , 𝑦 = 1 , 𝑧 = 2
  • C 𝑥 = 1 , 𝑦 = 2 , 𝑧 = 2
  • D 𝑥 = 2 , 𝑦 = 2 , 𝑧 = 1
  • E 𝑥 = 2 , 𝑦 = 1 , 𝑧 = 2

Q24:

In the steam reforming of natural gas, hydrogen is produced by reacting methane (CH)4 with water, according to the shown equation: CH+HOCO+H422𝑥𝑦𝑧.

The coefficients 𝑥, 𝑦, and 𝑧 are all whole numbers.

In which order are the coefficients 𝑥, 𝑦, and 𝑧 most easily determined.

  • A 𝑦 , 𝑥 , 𝑧
  • B 𝑥 , 𝑦 , 𝑧
  • C 𝑧 , 𝑦 , 𝑥
  • D 𝑦 , 𝑧 , 𝑥
  • E 𝑥 , 𝑧 , 𝑦

If the coefficient of CH4 is set to 1, as shown, what is the value of 𝑧?

Q25:

In the Haber process, ammonia (NH)3 is produced from nitrogen and hydrogen, according to the shown equation: 𝑥𝑦𝑧.N+HNH223 Determine the smallest possible whole number values of 𝑥, 𝑦, and 𝑧.

  • A 𝑥 = 1 , 𝑦 = 3 , 𝑧 = 2
  • B 𝑥 = 2 , 𝑦 = 3 , 𝑧 = 2
  • C 𝑥 = 2 , 𝑦 = 3 , 𝑧 = 3
  • D 𝑥 = 3 , 𝑦 = 2 , 𝑧 = 3
  • E 𝑥 = 1 , 𝑦 = 2 , 𝑧 = 3

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