6 Questions
What is the purpose of a chemical equation?
To show the identities and relative quantities of reactants and products in a reaction
Why do chemical reactions occur?
Because of the rearrangement of atoms and the breaking/forming of chemical bonds
What does balancing a chemical equation ensure?
It follows the law of conservation of mass by having equal numbers of each kind of atom on both sides
What is the purpose of numerical coefficients in chemical equations?
To show the molar ratio between reactants and products
In a balanced chemical equation, what does it mean if there are twice as many moles of NH₄₂Cr₂O₇ compared to the original equation?
The equation is balanced correctly
Which part of a chemical equation indicates how many molar equivalents of each substance are participating in the reaction?
Numerical coefficients before each substance name
Study Notes
Understanding Chemical Reactions and Equations
Chemical reactions involve transforming substances, called reactants, into entirely different substances, called products. These events occur due to the breaking and forming of chemical bonds between atoms. A chemical reaction is described through a chemical equation, which shows the identities and relative quantities of the reactants and products involved in the transformation.
Consider the classic example of heating ammonium dichromate (NH₄₆Cr₂O₁₇) to produce chromium(III) oxide (Cr₂O₃) and water. The unbalanced chemical equation for this reaction could be written as:
[ \mathrm{(NH₄)}_6\mathrm{Cr}2\mathrm{O}{17}(s)\rightarrow\mathrm{Cr}_2\mathrm{O}_3(s)+\mathrm{water~product}+\cdots ]
However, to follow the law of conservation of mass, we balance the equation based on the number of each kind of atom present. After balancing, the equation becomes:
[ \begin{aligned} &2(\mathrm{NH₄})_2\mathrm{Cr}_2\mathrm{O}_7(s)\rightarrow 2\mathrm{Cr}_2\mathrm{O}_3(s)\ &\quad+\quad6\mathrm{H}_2\mathrm{O}(g)+\cdots \end{aligned} ]
In this balanced version, there are twice as many moles of NH₄₂Cr₂O七 and Cr₂O三, and six times as many moles of H₂O compared to the original equation.
Chemical equations often contain numerical coefficients before each substance name, indicating how many molar equivalents of each substance are participating in the reaction. Additionally, physical states are usually indicated following the substance names: (s) for solid, (l) for liquid, and (g) for gas.
Different types of reactions exist depending on the products generated, including combustion, decomposition, neutralization, and synthesis. Each reaction type follows distinct patterns of behavior and produces characteristic products. Through the careful study of chemical reactions and equations, we gain valuable insight into the complex interactions governing our natural and technological worlds.
Test your knowledge on chemical reactions and equations by understanding the transformation of reactants into products through the breaking and forming of chemical bonds. Learn how to balance chemical equations to satisfy the law of conservation of mass and recognize different types of reactions like combustion, decomposition, neutralization, and synthesis.
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