Practice Chemical Equation in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

A written representation of a chemical reaction using chemical formulas for reactants and products, coefficients to indicate mole ratios, state symbols to show physical states.

A recipe that shows what goes in, what comes out, and in what amounts.

Showing a random 20 of 50 problems.

Example 1

challenge
A student writes H2O→H+OHH_2O \to H + OH for water 'decomposition.' Identify two errors in this equation.

Example 2

easy
Is 2H2+O2β†’2H2O2H_2 + O_2 \rightarrow 2H_2O balanced? Count hydrogen atoms on each side.

Example 3

easy
What does the state symbol (l)(l) represent?

Example 4

medium
Translate 2KClO3(s)β†’Ξ”2KCl(s)+3O2(g)2\text{KClO}_3\text{(s)} \xrightarrow{\Delta} 2\text{KCl(s)} + 3\text{O}_2\text{(g)} into a word equation.

Example 5

easy
In an equation, where do reactants and products go relative to the arrow?

Example 6

medium
For C4H10(g)+132O2(g)β†’4CO2(g)+5H2O(l)\text{C}_4\text{H}_{10}\text{(g)} + \dfrac{13}{2}\text{O}_2\text{(g)} \rightarrow 4\text{CO}_2\text{(g)} + 5\text{H}_2\text{O(l)}, write the equivalent equation with smallest whole-number coefficients.

Example 7

medium
Why is changing H2OH_2O to HOHO to 'balance' an equation wrong?

Example 8

easy
In 2Na+2H2O→2NaOH+H22\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2, what is the mole ratio of Na to H2H_2?

Example 9

easy
What information does a balanced chemical equation convey? Explain using 2H2+O2β†’2H2O2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O} as an example.

Example 10

easy
Write the unbalanced equation for solid magnesium reacting with hydrochloric acid to form aqueous magnesium chloride and hydrogen gas.

Example 11

medium
How does a balanced chemical equation embody conservation of mass?

Example 12

easy
What does the state symbol (aq)(aq) mean?

Example 13

challenge
A student balances Mg+O2β†’MgO\text{Mg} + O_2 \rightarrow MgO as Mg+O2β†’MgO2Mg + O_2 \rightarrow MgO_2. Identify the error and give the correct balanced equation.

Example 14

medium
Write a balanced chemical equation with state symbols for the reaction of solid iron with oxygen gas to form solid iron(III) oxide.

Example 15

easy
What symbol indicates that heat is supplied to a reaction?

Example 16

medium
Add state symbols: solid zinc plus aqueous hydrochloric acid gives aqueous zinc chloride plus hydrogen gas.

Example 17

medium
Write the balanced equation with state symbols for solid calcium carbonate reacting with aqueous HCl to give aqueous calcium chloride, water, and carbon dioxide gas.

Example 18

hard
A student writes the following unbalanced equation for the reaction of aluminum with sulfuric acid: Al+H2SO4β†’Al2(SO4)3+H2\text{Al} + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2. Balance this equation and verify by counting all atoms on each side.

Example 19

easy
What symbol shows a reversible reaction?

Example 20

hard
Write the balanced ionic equation for AgNO3(aq)+NaCl(aq)β†’AgCl(s)+NaNO3(aq)\text{AgNO}_3\text{(aq)} + \text{NaCl(aq)} \rightarrow \text{AgCl(s)} + \text{NaNO}_3\text{(aq)}.
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