9.3: Writing Chemical Equations
- Page ID
- 451548
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Given a sentence that describes a chemical reaction write a balanced chemical equation.
To turn a description of a chemical reaction into a balanced chemical equation, we need to follow the given steps:
- Identify the reactants and products. This will help you know which symbols go on each side of the arrow and where the \(+\) signs go.
- Write the correct formulas for all compounds. You will need to use the rules you learned in the chapters covering ionic compounds and covalent compounds.
- Write the correct formulas for all elements. Usually this is given straight off of the periodic table. However, there are seven elements that are considered diatomic, meaning that they are always found in pairs in nature. They include those elements listed in the table below.
- Add phase labels to indicate whether the substances are solids, liquids, gases, or aqueous.
- Finally, balance the equation. This should always be the final step.
| Element Name | Hydrogen | Nitrogen | Oxygen | Fluorine | Chlorine | Bromine | Iodine |
|---|---|---|---|---|---|---|---|
| Formula | \(H_2\) | \(N_2\) | \(O_2\) | \(F_2\) | \(Cl_2\) | \(Br_2\) | \(I_2\) |
Transfer the following symbolic equations into word equations or word equations into symbolic equations.
- Gaseous propane, \(\ce{C_3H_8}\), burns in oxygen to produce gaseous carbon dioxide and water vapor.
- Hydrogen fluoride gas reacts with an aqueous solution of potassium carbonate to produce an aqueous solution of potassium fluoride, liquid water, and gaseous carbon dioxide.
Solution
a.
Reactants: propane (\(\ce{C_3H_8}\)) and oxygen (\(\ce{O_2}\))
Products: carbon dioxide (\(\ce{CO_2}\)) and water (\(\ce{H_2O}\))
Unbalanced chemical equation:
\[\ce{C_3H_8} \left( g \right) + \ce{O_2} \left( g \right) \rightarrow \ce{CO_2} \left( g \right) + \ce{H_2O} \left( l \right) \nonumber \]
Balanced chemical equation:
\[\ce{C_3H_8} \left( g \right) + 5\ce{O_2} \left( g \right) \rightarrow 3\ce{CO_2} \left( g \right) + 4\ce{H_2O} \left( l \right) \nonumber \]
b.
Reactants: hydrogen fluoride (\(\ce{HF}\)) and potassium carbonate (\(\ce{K_2CO_3}\))
Products: potassium fluoride (\(\ce{KF}\)), water (\(\ce{H_2O}\)), and carbon dioxide (\(\ce{CO_2}\))
Unbalanced chemical equation:
\[\ce{HF} \left( g \right) + \ce{K_2CO_3} \left( aq \right) \rightarrow \ce{KF} \left( aq \right) + \ce{H_2O} \left( l \right) + \ce{CO_2} \left( g \right) \nonumber\]
Balanced chemical equation:
\[2\ce{HF} \left( g \right) + \ce{K_2CO_3} \left( aq \right) \rightarrow 2\ce{KF} \left( aq \right) + \ce{H_2O} \left( l \right) + \ce{CO_2} \left( g \right) \nonumber\]
Transfer the following symbolic equations into word equations or word equations into symbolic equations.
- Hydrogen reacts with nitrogen to produce gaseous ammonia.
- Copper metal is heated with oxygen to produce solid copper(II) oxide.
- Answer a
- \(3H_2 (g) + N_2 (g) \rightarrow 2NH_3 (g)\)
- Answer b
- \(2Cu (s) + O_2 (g) \rightarrow 2CuO (s)\)