Molecular Chemistry Introduction

Introduction to the Mole

with formula writing review

Multiple Choice

In a plastic bottle of water (16 oz) are there more or less than 602 sextillion water molecules?

• more

• less

The Mole

• A counting number = 6.02 x 10²³ of ANYTHING.

• Why is it important? Because 1 mole of an atoms of any element weighs it's atomic mass in grams.

Scientific Notation on Your Calculator

Two choices:

• Use the ^ button, but make sure you put your entire number in parentheses.
• Use the EE button. It takes the place of (x 10^) in your number. 6.02E23

Dimensional Analysis - Unit Conversions

• In this class, we will need to convert between units ALOT!

• There are several different ways to do this, but I want you to use THIS method.

• You will have to show your work on written questions.

Question

Earth is 3.208 x 10¹¹ miles from Pluto.  If a light year is equal to 5.879 x 10¹² miles, how many light years is Earth from Pluto?

Answer

When doing the math, complete the question like you were reading it to someone.

3.02E11 x 1 / 5.879E12

We get 0.0514 light years.

Molar Mass

• The average atomic mass on the periodic table tells the weighted average of all naturally occurring isotopes. (For an atom in amu.)

• If you have a sample of the element with a mass of that value in GRAMS, you will have exactly one mole of atoms

• 10.81 grams of Boron contains 6.02 x 10²³ atoms of Boron.

Fill in the Blanks

This is true for molecules as well.

• If I have one mole of CO₂ molecules, there will be one mole of C atoms and 2 moles of O atoms. The mass of one mole of CO₂ molecules is (12.011 + 15.999*2) = 44.009 grams.

• We can round to the 10ths place (44.0 g)

Fill in the Blanks

Multiple Choice

What is the chemical formula for sodium bromide?

• NaBr

• SBr

• Na₂Br

• Na₇Br

Fill in the Blanks

Conversion Factors

• 1 mole = 6.02 x 10²³ atoms (molecules)

• 1 mole = molar mass in grams

• Molar mass comes from the Periodic Table and is different for each element or compound.

Multiple Choice

For the question: "How many grams in 1.35 moles of Na?" We start by writing what you see in the picture. What will be on the BOTTOM of the conversion factor?

• 1 mole Na

• 1 gram Na

• 22.99 moles Na

• 6.02 x 10²³ moles Na

• 6.02 x 10²³ atoms Na

Open Ended

9.03 x 10²³ atoms of aluminum will have a mass of ____ grams.