Honors Chemistry Notes

Honors Chemistry

The Honors Chemistry course requires a strong foundation in math, specifically:

• Algebra (understanding variables and constants)

• Interpreting graphs

• Logarithms

These math skills are needed throughout the course.

Science-Specific Skills

• Scientific notation

• Dimensional analysis

• Significant figures

A math test will be given to all Honors Chemistry students, with no in-class review, as these skills are pre-requisite. Students must also memorize the polyatomic ions listed on paper notecards.

Summer Expectations

Students should create flashcards for the listed ions and memorize them over the summer. Quizzes on the ions will begin the first week back in August. Flashcards are due on the first day.

Example:

• NO3- : Nitrate

• OH- : Hydroxide

An ion is an atom or group of atoms with a charge, having gained or lost 1, 2, or 3 electrons.

• Simple ion: A single atom with a charge (e.g., F- is the fluoride ion).

• Polyatomic ion: A group of atoms with a charge (e.g., OH- hydroxide ion, NH4+ ammonium ion, SO42- sulfate ion).

Chemistry Nomenclature

Memorizing chemistry symbols and ions is like memorizing letters in a foreign language. Learning chemistry nomenclature (naming) is similar to learning a foreign language and requires paying attention to patterns. Just as you learn the alphabet before you learn to spell, you need to learn the elements and ions before you can write formulas and balance equations.

• Na+ is sodium, Br- is bromide ion. NaBr = sodium bromide

Soon, you will put these together into balanced equations. You can't write a formula if you don't know your ions!

You are required to have these memorized.

Polyatomic Ions

1- Charge

• $OH^{-1}$ hydroxide

• $NO_3^{-1}$ nitrate

• $SCN^{-1}$ thiocyanate

• $CN^{-1}$ cyanide

• $NO_2^{-1}$ nitrite

• $ClO_4^{-1}$ perchlorate

• $ClO_3^{-1}$ chlorate

• $ClO_2^{-1}$ chlorite

• $ClO^{-1}$ hypochlorite

• $FO_4^{-1}$ perfluorate

• $FO_3^{-1}$ fluorate

• $HSO_4^{-1}$ hydrogen sulfate (bisulfate)

• $HSO_3^{-1}$ hydrogen sulfite (bisulfite)

• $HCO_3^{-1}$ hydrogen carbonate

• $BrO_4^{-1}$ perbromate

• $BrO_3^{-1}$ bromate

• $BrO_2^{-1}$ bromite

• $BrO^{-1}$ hypobromite

• $IO_4^{-1}$ periodate

• $IO_3^{-1}$ iodate

• $IO_2^{-1}$ iodite

• $IO^{-1}$ hypoiodite

• $C<em>2H</em>3O_2^{-1}$ acetate

• $FO_2^{-1}$ fluorite

• $FO^{-1}$ hypofluorite

• $H<em>2PO</em>4^{-1}$ dihydrogen phosphate

2- Charge

• $SO_4^{-2}$ sulfate

• $SO_3^{-2}$ sulfite

• $CO_3^{-2}$ carbonate

• $CrO_4^{-2}$ chromate

• $Cr<em>2O</em>7^{-2}$ dichromate

• $O_2^{-2}$ peroxide

• $C<em>2O</em>4^{-2}$ oxalate

• $HPO_4^{-2}$ hydrogen phosphate (biphosphate)

• tartrate

3- Charge

• $PO_4^{-3}$ phosphate

• $PO_3^{-3}$ phosphite

Positive Polyatomics

• $NH_4^{+1}$ ammonium

• $H_3O^{+}$ hydronium

PER = MORE OXYGEN, Hypo = LESS OXYGEN

Temperature Scales

• Celsius (°C) - used in most of the world and in science

• Fahrenheit (°F) - used in the United States

Conversion Formulas

• Celsius to Fahrenheit: $F = \frac{9}{5}C + 32$

• Fahrenheit to Celsius: $C = \frac{5}{9}(F - 32)$

Examples

1. Convert 0°C to Fahrenheit: $F = \frac{9}{5}(0) + 32 = 32°F$

2. Convert 77°F to Celsius: $C = \frac{5}{9}(77 - 32) = \frac{5}{9}(45) = 25°C$

Practice Conversions

Celsius to Fahrenheit

1. 10°C = 50°F

2. 25°C = 77°F

3. -23°C = -9.4°F

4. 100°C = 212°F

Fahrenheit to Celsius

5. 68°F = 20°C

6. 32°F = 0°C

7. 212°F = 100°C

8. -4°F = -20°C

9. What is the temperature where Celsius and Fahrenheit are equal?

   • Equation: $C = \frac{5}{9}(C - 32)$

   • Answer: C = -40

10. Room temperature is about 72°F. What is that in Celsius?

    • 22.2°C

Kelvin Scale

Scientists use the Kelvin scale because it's based on absolute temperature.

Formula

• $K = C + 273$

• $C = K - 273$

Conversions

11. 0°C = 273 K

12. -50°C = 223 K

13. 100°C = 373 K

Solubility Curve

A solubility curve shows how much of a substance (solute) can dissolve in a solvent (usually water) at different temperatures.

• Solubility is usually measured in grams of solute per 100 g of water.

• As temperature increases, most substances become more soluble.

Solubility Data for Potassium Nitrate (KNO3)

Instructions

1. Label the x-axis as Temperature (°C) and the y-axis as Solubility (g/100g water).

2. Use a scale that fits all the data.

3. Plot each point from the table above.

4. Connect the points with a smooth, curved line.

5. Title your graph.

Questions

1. At what temperature does KNO3 reach a solubility of 100 g/100g water?

2. How much KNO3 dissolves at 25°C? (Estimate from your graph.)

Density

Density is a measure of how much mass is contained in a given volume.

Formula

$Density = \frac{Mass}{Volume}$, or $D = \frac{m}{V}$

Units

Common units include g/cm³, kg/m³, or g/mL.

A denser object has more mass packed into the same amount of space.

Practice Problems

Show your work and include correct units.

1. A metal cube has a mass of 240 grams and a volume of 30 cm³. What is its density?

2. A liquid has a volume of 50 mL and a density of 0.8 g/mL. What is its mass?

3. An irregular object has a mass of 75 g and displaces 25 mL of water. What is the object's density?

4. A block has a density of 2.5 g/cm³ and a mass of 100 g. What is its volume?

Dimensional Analysis

Dimensional analysis (also called the factor-label method or unit conversion) is a problem-solving method that uses conversion factors to move from one unit to another.

Example

Convert 120 inches to feet.

Conversion factor: 1 ft = 12 in

$120 \text{ in} \times \frac{1 \text{ ft}}{12 \text{ in}} = 10 \text{ ft}$

Conversion Factors and Dimensional Analysis

Guiding Principles

1. When the numerator and the denominator are the same, then the fraction equals one.

2. When any number is multiplied by one, you do not change the number at all.

A conversion factor is a fraction that equals one, since the top and the bottom are the same thing, just expressed in different units.

Examples of conversion factors

• $\frac{1 \text{ dollar}}{10 \text{ dimes}}$

• $\frac{12 \text{ inches}}{1 \text{ foot}}$

• $\frac{365 \text{ days}}{1 \text{ year}}$

• $\frac{5280 \text{ feet}}{1 \text{ mile}}$

• $\frac{1760 \text{ yards}}{5280 \text{ feet}}$

• $\frac{12 \text{ eggs}}{1 \text{ dozen}}$

Steps

1. What unit has to go on the bottom to cancel?

2. What can I change that unit into?

3. What numbers will make them equal?

Practice Problems

Single-Step Conversions

1. Convert 500 mL to liters. (use 1000mL=1.0L)

   $500 \text{ mL} \times \frac{1.0 \text{ L}}{1000 \text{ mL}} = 0.5 \text{ L}$

2. Convert 3.5 feet to inches. (12 inches = 1 foot)

   $3.5 \text{ ft} \times \frac{12 \text{ in}}{1 \text{ ft}} = 42 \text{ in}$

3. Convert 2500 grams to kilograms. (1000g = 1kg)

   $2500 \text{ g} \times \frac{1 \text{ kg}}{1000 \text{ g}} = 2.5 \text{ kg}$

4. Convert 2 hours to seconds. (1 hour = 3600sec)

   $2 \text{ hr} \times \frac{3600 \text{ sec}}{1 \text{ hr}} = 7200 \text{ sec}$

Multi-Step Conversions

5. Convert 120 minutes to days.

   $120 \text{ min} \times \frac{1 \text{ hr}}{60 \text{ min}} \times \frac{1 \text{ day}}{24 \text{ hr}} = 0.0833 \text{ days}$

6. Convert 5.2 kilometers to inches. (Use: 1 km = 1000 m, 1 m = 100 cm, 1 in = 2.54 cm)

   $5.2 \text{ km} \times \frac{1000 \text{ m}}{1 \text{ km}} \times \frac{100 \text{ cm}}{1 \text{ m}} \times \frac{1 \text{ in}}{2.54 \text{ cm}} = 204724 \text{ in}$

7. Convert 60 miles per hour to meters per second. (Use: 1 mile = 1609 m, 1 hour = 3600 s)

   $60 \frac{\text{miles}}{\text{hr}} \times \frac{1609 \text{ m}}{1 \text{ mile}} \times \frac{1 \text{ hr}}{3600 \text{ s}} = 26.8 \frac{\text{m}}{\text{s}}$

8. Convert 250 cm³ to liters. (Use: 1000 cm³ = 1 L)

   $$250 \text{ cm}^3 \times \frac