AP Chemistry Summer Assignment Notes

AP Chemistry Course Overview and Summer Assignment Expectations

AP Chemistry is designed to be the equivalent of a first-year college chemistry course. To ensure students are prepared for the rigor of the upcoming year, a mandatory summer assignment must be completed and submitted on the first day of school. While the assignment is not lengthy, it is critical for establishing the foundation necessary for success.

A quiz covering the summer assignment material will be administered during the first week of school. Students are expected to come prepared to demonstrate mastery of the following areas:

Ions: Mastery of formulas, charges, and names of common ions.
Significant Figures: Proficiency in applying rules for measurements and calculations.

Part 1: Memorization of Common Ions

Students must memorize the formulas, charges, and names of common ions. Unlike Regents Chemistry, these will not be provided on a reference table during assessments. On the introductory quiz, students will be required to:

Provide the name of an ion when given its formula and charge.
Provide the formula and charge when given the name of an ion.

Note that the periodic table used in AP Chemistry is simplified and only provides element symbols, not names.

Cations to Memorize

Symbol	Name	Symbol	Name
$H^+$	Hydrogen	$Ag^+$	Silver
$Li^+$	Lithium	$Zn^{2+}$	Zinc
$Na^+$	Sodium	$Hg_2^{2+}$	Mercury(I)
$K^+$	Potassium	$NH_4^+$	Ammonium
$Rb^+$	Rubidium	$Cs^+$	Cesium
$Be^{2+}$	Beryllium	$Mg^{2+}$	Magnesium
$Ca^{2+}$	Calcium	$Ba^{2+}$	Barium
$Sr^{2+}$	Strontium	$Al^{3+}$	Aluminum

Type II Cations (Variable Charge)

Symbol	Name	Symbol	Name
$Fe^{3+}$	Iron(III)	$Fe^{2+}$	Iron(II)
$Cu^{2+}$	Copper(II)	$Cu^+$	Copper(I)
$Co^{3+}$	Cobalt(III)	$Co^{2+}$	Cobalt(II)
$Sn^{4+}$	Tin(IV)	$Sn^{2+}$	Tin(II)
$Pb^{4+}$	Lead(IV)	$Pb^{2+}$	Lead(II)
$Hg^{2+}$	Mercury(II)

Anions to Memorize

Symbol	Name	Symbol	Name
$NO_2^-$	Nitrite	$NO_3^-$	Nitrate
$SO_3^{2-}$	Sulfite	$SO_4^{2-}$	Sulfate
$HSO_4^-$	Hydrogen sulfate (bisulfate)	$OH^-$	Hydroxide
$CN^-$	Cyanide	$H^-$	Hydride
$PO_4^{3-}$	Phosphate	$HPO_4^{2-}$	Hydrogen phosphate
$H_2PO_4^-$	Dihydrogen phosphate	$NCS^-$	Thiocyanate
$F^-$	Fluoride	$Cl^-$	Chloride
$Br^-$	Bromide	$I^-$	Iodide
$O^{2-}$	Oxide	$S^{2-}$	Sulfide
$Se^{2-}$	Selenide	$N^{3-}$	Nitride
$P^{3-}$	Phosphide	$As^{3-}$	Arsenide
$CO_3^{2-}$	Carbonate	$HCO_3^-$	Hydrogen carbonate (bicarbonate)
$ClO^-$	Hypochlorite	$ClO_2^-$	Chlorite
$ClO_3^-$	Chlorate	$ClO_4^-$	Perchlorate
$BrO^-$	Hypobromite	$BrO_2^-$	Bromite
$BrO_3^-$	Bromate	$BrO_4^-$	Perbromate
$IO^-$	Hypoiodite	$IO_2^-$	Iodite
$IO_3^-$	Iodate	$IO_4^-$	Periodate
$C_2H_3O_2^-$	Acetate	$MnO_4^-$	Permanganate
$Cr_2O_7^{2-}$	Dichromate	$CrO_4^{2-}$	Chromate
$O_2^{2-}$	Peroxide	$C_2O_4^{2-}$	Oxalate
$NH_2^-$	Amide	$BO_3^{3-}$	Borate
$S_2O_3^{2-}$	Thiosulfate

Systematic Patterns for Ion Memorization

Efficient memorization relies on identifying patterns based on the periodic table and nomenclature rules.

1. Periodic Table Trends

Neutral atoms gain or lose electrons to reach a noble gas configuration, resulting in predictable charges based on their group:

Group 1 (Alkali Metals): Lose 1 electron to form a $1+$ charge.
Group 2 (Alkaline Earth Metals): Lose 2 electrons to form a $2+$ charge.
Group 13 Metals (e.g., Aluminum): Lose 3 electrons to form a $3+$ charge.
Group 17 (Halogens): Gain 1 electron to form a $1-$ charge.
Group 16 Nonmetals: Gain 2 electrons to form a $2-$ charge.
Group 15 Nonmetals: Gain 3 electrons to form a $3-$ charge.

Nomenclature Note: Cations retain their element name (e.g., sodium ion), while monatomic anions use the "-ide" suffix (e.g., sulfide ion).

2. Metals with Multiple Oxidation States

Metals capable of forming more than one ion use a Roman numeral in parentheses to indicate the positive charge (e.g., Iron(III) for $Fe^{3+}$ ).

3. Polyatomic Anion Series

-ate vs. -ite: The "-ate" form has one more oxygen atom than the "-ite" form, but the charge remains the same.
- Sulfate ( $SO_4^{2-}$ ) vs. Sulfite ( $SO_3^{2-}$ ).
- Nitrate ( $NO_3^-$ ) vs. Nitrite ( $NO_2^-$ ).
Hydrogen Addition: Adding a hydrogen ion ( $H^+$ ) to a polyatomic anion reduces the negative charge by one.
- Phosphate ( $PO_4^{3-}$ ) $\rightarrow$ Hydrogen phosphate ( $HPO_4^{2-}$ ) $\rightarrow$ Dihydrogen phosphate ( $H_2PO_4^-$ ).
Halogen-Oxygen Series:
- Prefix "hypo-": Means "under" or "too little" (e.g., Hypochlorite has one less oxygen than chlorite).
- Prefix "per-": Derived from "hyper-" meaning "above" or "too much" (e.g., Perchlorate has one more oxygen than chlorate).
- Increasing Oxygen Sequence: $ClO^-$ (hypochlorite) $\rightarrow$ $ClO_2^-$ (chlorite) $\rightarrow$ $ClO_3^-$ (chlorate) $\rightarrow$ $ClO_4^-$ (perchlorate).

Principles of Significant Figures in Measurement

Significant figures represent the reliability of a number. In chemistry, calculations should only include figures that are considered reliable to avoid wasting effort and reporting false precision.

Definition of Significant Figures

A measurement consists of:

All digits known with certainty.
One final digit that is estimated (a "guess").

Recording Measurements from Instruments

When reading a manual instrument (ruler, thermometer, etc.), the user must record all certain digits plus one estimated digit.

Example A: A measurement is clearly past $7.8\,cm$ . The next digit is estimated as five-tenths of the way to $7.9$ . The recorded value is $7.85\,cm$ (three significant figures).
Example B: A measurement is exactly on the $9.2\,cm$ mark. The estimated digit is zero. The value is reported as $9.20\,cm$ (three significant figures).

Rules for Zeros

Zero Within a Number: Zeros between non-zero digits are always significant (e.g., $9.04$ has three significant figures).
Zero at the Front: Leading zeros are placeholders only and are never significant (e.g., $0.07$ has one significant figure; $0.46$ has two).
Zero at the End (After Decimal): Trailing zeros after a decimal point are significant because they indicate the precision of the measurement (e.g., $11.30\,cm$ has four significant figures; $0.020\,ml$ has two).
Zero at the End of Whole Numbers: These may or may not be significant. Using scientific notation clarifies the precision.
- $1600\,ft$ is assumed to have two sig figs.
- $1.6 \times 10^3\,ft$ (two sig figs).
- $1.60 \times 10^3\,ft$ (three sig figs).
- $1.600 \times 10^3\,ft$ (four sig figs).

Rules for Rounding and Mathematical Operations

General Rounding Rules

If the digit to be dropped is less than 5, simply drop it.
If the digit to be dropped is greater than 5, round the preceding digit up by 1.
If the digit to be dropped is exactly 5 and followed by non-zero digits, round up.
If the digit is exactly 5 (not followed by non-zero digits) and preceded by an odd digit, round up.
If the digit is exactly 5 (not followed by non-zero digits) and preceded by an even digit, the preceding digit remains unchanged.

Rounding Examples (to three significant figures):

$3.478\,m \rightarrow 3.48\,m$
$4.8055\,cm \rightarrow 4.81\,cm$
$5.333\,g \rightarrow 5.33\,g$
$7.999\,in. \rightarrow 8.00\,in.$

Arithmetic Operations

Multiplication and Division: The result must have the same number of significant figures as the factor with the least number of significant figures.

Example 1: $0.024 \times 1244$ . Factor $0.024$ has two sig figs. The answer must be rounded to two sig figs.
Example 2: Area = $2.1\,cm \times 3.24\,cm = 6.804\,cm^2$ . Reported as $6.8\,cm^2$ (two sig figs).
Example 3: Volume = $10.2\,cm \times 8.24\,cm \times 1.8\,cm = 151.2864\,cm^3$ . Reported as $150\,cm^3$ (two sig figs).
Example 4: $20.45 \div 2.4 = 8.52083$ . Reported as $8.5$ (two sig figs).

Addition and Subtraction: The result must round to the least number of decimal places found in the data.

Example: $42.56\,g + 39.460\,g + 4.1\,g = 86.120\,g$ . Since $4.1\,g$ only has one decimal place, the answer is $86.1\,g$ .

Average Readings: When averaging, the final result should match the decimal places of the sum. Note that the divisor in an average (e.g., dividing by 3) is an exact number and does not limit the significant figures of the result.

Example: Average of $12.523\,g$ , $12.497\,g$ , and $12.515\,g$ .
Sum = $37.535\,g$
Average = $37.535 \div 3 = 12.51167$
Final answer: $12.512\,g$ (rounded to match the three decimal places of the sum).

Graded Significant Figure Assignment Exercises

Significant Figure Counts

Identify the number of significant figures in the following:

$402\,m$
$0.00420\,g$
$5.1 \times 10^4\,kg$
$34.20\,lbs$
$3200\,liters$
$0.48\,m$
$0.03\,sec$
$0.0300\,ft$
$1400.0\,m$
$1.10\,torr$
$760\,mm\,Hg$
$78323.01\,g$

Multiplication and Division Practice

Apply sig fig rules and include units:

$17\,m \times 324\,m$
$1.7\,mm \times 4294\,mm$
$0.005\,in \times 8888\,in$
$0.050\,m \times 102\,m$
$0.424\,in \times 0.090\,in$
$324000\,cm \times 12.00\,cm$
$23.4\,m \div 0.50\,sec$
$12\,miles \div 3.20\,hours$
$0.960\,g \div 1.51\,moles$
$1200\,m \div 12.12\,sec$

Addition and Subtraction Practice

$3.40\,m + 0.022\,m + 0.5\,m$
$102.45\,g + 2.44\,g + 1.9999\,g$
$102.\,cm + 3.14\,cm + 5.9\,cm$
$42.306\,m - 1.22\,m$
$14.33\,g - 3.468\,g$
$234.1\,cm - 62.04\,cm$

Applied Problems

Chemical Determination: Three determinations of the percentage of oxygen in mercuric oxide yielded $7.40\%$ , $7.43\%$ , and $7.35\%$ . Calculate the average percentage.
Volume Calculation: A rectangular solid measures $13.4\,cm \times 11.0\,cm \times 2.2\,cm$ . Calculate the volume.
Density and Mass (Mercury): If the density of mercury is $13.6\,g/mL$ , find the mass in grams of $3426\,mL$ of the liquid.
Cylinder Mass (Copper): A copper cylinder has a radius of $12.0\,cm$ and a length of $44.0\,cm$ . If the density of copper is $8.90\,g/cm^3$ , calculate the mass in grams. (Assume $\pi = 3.14$ ).