3.1: Chemistry Review
- Page ID
- 42429
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The Periodic Table of Elements
The periodic table of elements is a map of all known chemical elements organized by their atomic number, electron configuration, and chemical properties. Groups refer to columns in the table, and periods refer to the rows. Based on an element's position in the table, scientists can predict how an element will interact with other types of elements.
Stoichiometry
Stoichiometry quantifies the relationships between reactants and products in a chemical reaction. Based on a balanced chemical equation, stoichiometry can determine the amounts of substances consumed and produced in a reaction. Substances can be compared by mole ratios and mass ratios.
Balancing chemical equations is a necessary first step. To achieve a balanced equation, the quantity of specific elements on the reactants side (left side) needs to equal the quantity of specific elements on the products side (right side). Begin by writing out the chemical equation, then balance the metals, non-metals, and oxygen.
Write the balanced chemical equation for when magnesium metal undergoes combustion to produce magnesium oxide.
Solution
Write out the reactants and products of the equation
Mg + O2 --> MgO
Count the number of each atom on the reactants and products sides of the equation
| Reactants | Products | ||
|---|---|---|---|
| Mg | 1 | Mg | 2 |
| O | 2 | O | 2 |
Use whole-number coefficients to balance each side
- Since there are two oxygen on the reactants, add a coefficient of 2 for the products
Mg + O2 --> 2 MgO
- Now the oxygen is balanced, but the products side has two magnesium, while the reactants side has one.
- Add a coefficient of 2 before magnesium on the reactants side
2 Mg + O2 --> 2 MgO
- Recount the number of each atom on the reactants and products sides of the equation. They should be equal
| Reactants | Products | ||
|---|---|---|---|
| Mg | 2 | Mg | 2 |
| O | 2 | O | 2 |
You have found your balanced equation
2 Mg + O2 --> 2 MgO
Electronegativity
Electronegativity is a measure of an atom's ability to attract and hold onto electrons within a chemical bond. It plays a crucial role in determining the nature of chemical bonds and the behavior of molecules. Here's how it relates to the periodic table:
-
Trend Across Periods: Electronegativity generally increases as you move from left to right across a period. This is because atoms have more protons in their nuclei, which increases their ability to attract electrons.
-
Trend Down Groups: Electronegativity decreases as you move down a group. This is due to the increasing distance between the nucleus and the valence electrons, which reduces the nucleus's pull on the electrons.
Electronegativity plays a role in chemical bond types. Ionic bonds occur when there is a large difference in electronegativity. This difference leads to the transfer of electrons from one element to another and typically happens between metals and non-metals (e.g., NaCl). Covalent bonds occur when there is a small difference in electronegativity. In covalent bonds, each atom contributes electrons to the bond, which exist in overlapping orbitals. Water (H2O) is a classic example of a compound with covalent bonds. In a water molecule, each hydrogen atom shares one electron with the oxygen atom.
pH
pH is a scale measuring hydrogen ion concentrations in water. The scale ranges from 0 to 14, with low numbers indicating acidity, 7 representing neutral, and high numbers indicating basicity. The pH scale is logarithmic, so each whole-number change represents a factor of ten in hydrogen ion concentration.
Many chemical reactions are driven by the solution's pH level. The rate of reaction and the equilibrium point can change as pH increases or decreases. In water, changes in pH can modify nutrient availability. While this can negatively impact the environment, water treatment facilities use pH to their advantage when treating water. Adjusting the pH can optimize water treatment processes and decrease the overall chemical needs.