# CHEM109 Chemistry Fundamentals

The following topics are covered in this booklet;

Significant Figures

Temperature

Mass

Volume

Density Calculations

Naming Ionic Compounds

Writing Ionic Formulae

Empirical and Molecular Formula

Balancing Chemical Equations

Writing Equations: Precipitation Reactions

Percent Composition (Percentage Composition)

Definitions of a mole

Mass-Mole Calculations (n = mass ÷ MM)

Concentration of Solutions Calculations (M = n ÷ V)

Dilution of Solutions Calculations (M1V1=M2V2)

Reaction Calculations: Mass and Moles

Limiting Reagents & Reactants in Excess

Yield

Significant FiguresKey Concepts

Scientific notation, or exponential notation, is a convenient way to write down a very large or a very small number.

In scientific notation each number is written as a product of two numbers:

a coefficient x 10an exponent

Coefficients are usually expressed with one digit to the left of the decimal point.

An exponent gives the position of the decimal point in the number and is either:

positive (generally for numbers greater than or equal to 10)

zero (generally for numbers between 0 and 10)

negative (generally for numbers less than 0)

Converting a Number to Scientific (exponential) Notation

Write 0.015 in scientific (exponential) notation.

Step1, write the coefficient : 1.5

Step 2, count the places between the current decimal place and its position in the coefficient: 2

Step 3, determine the sign of the exponent. Moving to the right gives a negative sign (the number is less than 0): -

Finally write the number in scientific notation: 1.5 x 10-2

Write 256.35 in scientific (exponential) notation.

Step1, write the coefficient : 2.5635

Step 2, count the places between the current decimal place and its position in the coefficient: 2

Step 3, determine the sign of the exponent. Moving to the left gives a positive sign (the number is greater than 10): +

Finally write the number in scientific notation: 2.5635 x 10+2 which is usually written as 2.5635 x 102

Write 42.76 in scientific (exponential) notation.

Step1, write the coefficient : 4.276

Step 2, count the places between the current decimal place and its position in the coefficient: 1

Step 3, determine the sign of the exponent. Moving to the left gives a positive sign (the number is greater than 10): +

Finally write the number in scientific notation: 4.276 x 101

Write the number 3.56 in scientific (exponential) notation.

Step1, write the coefficient : 3.56

Step 2, count the places between the current decimal place and its position in the coefficient: 0

Zero is neither positive nor negative in sign.

Finally write the number in scientific notation: 3.56 x 100

Converting Scientific (exponential) Notation to a Decimal System Number

Write 1.23 x 103 as a decimal system number.

Step1, decide which way the decimal point will move based on whether the exponent is positive (move to right) or negative (move to left) : + therefore moves to right (number is greater than 10)

Step 2, decide how many places the decimal point will move based on the size of the exponent: 3 places

Finally write the number using zeroes to fill in the places between the decimal point in the coefficient and in the new number: 1230

Write 4.76 x 10-2 as a decimal system number.

Step1, decide which way the decimal point will move based on whether the exponent is positive (move to right) or negative (move to left) : - therefore moves to left (number is less than 0)

Step 2, decide how many places the decimal point will move based on the size of the exponent: 2 places

Finally write the number using zeroes to fill in the places between the decimal point in the coefficient and in the new number : 0.0467

Write 5.22 x 101 as a decimal system number.

Step1, decide which way the decimal point will move based on whether the exponent is positive (move to right) or negative (move to left) : + therefore moves to right (number is greater than 10)

Step 2, decide how many places the decimal point will move based on the size of the exponent: 1 place

Finally write the number using zeroes to fill in the places between the decimal point in the coefficient and in the new number if necessary: 52.2

TemperatureKey Concepts

Temperature is a measure of the average kinetic energy of the particles in an object.

Adding energy, eg, heat, to an object increases the kinetic energy of the particles which is observed as an increase in temperature.

When an object loses energy, kinetic energy of the particles decreases and is observed as a decrease in temperature.

Several temperature scales are in common use:

Kelvin Scale based on the kelvin unit (K), the SI unit of temperature.

Celsius Scale based on degrees Celsius (oC), closely related to the Centigrade scale.

Fahrenheit Scale based on degrees Fahrenheit (oF), commonly used in North America.

Kelvin Scale is based on the following fixed points:

The zero point is absolute zero, the lowest temperature theoretically obtainable.

The temperature at which solid, liquid and gaseous water can coexist indefinitely (the triple-point tempera-ture of water) is assigned a value of 273.16K

Celsius Scale is based on a triple-point temperature of water of 0.01oC, and at 1atm pressure a freezing point of 0.00oC and a boiling point of 100.00oC.

Celsius units (oC) are the same size as kelvin units (K).

Fahrenheit Scale is based on a freezing point of water of 32oF and a boiling point of 212oF.

Temperature Conversions

Converting Celsius (oC) to kelvin (K)

kelvin (K) = oC + 273.15

Converting kelvin (K) to Celsius (oC)

oC = K - 273.15

Converting Fahrenheit (oF) to Celsius (oC)

oC = 5/9 x (oF - 32)

Converting Celsius (oC) to Fahrenheit (oF)

oF = (9/5 x oC) + 32

Examples of Temperature Conversions

Convert 100oC to kelvin

kelvin (K) = oC + 273.15

K = 100 + 273.15 = 373.15K

Convert 298.15K to Celsius

oC = K - 273.15

oC = 298.15 - 273.15 = 25oC

Convert 212oF to Celsius

oC = 5/9 x (oF - 32)

oC = 5/9 x (212 - 32) = 100oC

Convert 30oC to Fahrenheit

oF = (9/5 x oC) + 32

oF = (9/5 x 30) + 32 = 86oF

Convert 80oF to kelvin

Convert oF to oC

oC = 5/9 x (oF - 32)

oC = 5/9 x (80 - 32) = 26.67oC

Convert oC to K

K = oC + 273.15

K = 26.67 + 273.15 = 299.82K

Convert 293.15K to Fahrenheit

Convert K to oC

oC = K - 273.15

oC = 293.15 - 273.15 = 20oC

Convert oC to oF

oF = (9/5 x oC) + 32

oF = (9/5 x 20) + 32 = 68oF

MassKey Concepts

Mass is a direct measure of the amount of matter in an object.

The SI unit of mass is the kilogram which is given the symbol kg .

Chemists in a laboratory usually deal with much smaller masses than kilograms, often grams or milligrams, so we need to be able to convert from one unit of mass to another.

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