Chapter 8 - Chemical Composition

Chapter 8 - Chemical Composition

Please read the lesson slides and answer the quiz slides. Upload all work to Google Classroom after completing the assignment.

First, let's review what we learned on Tuesday.

Read the following slide and recall that we are using two conversion factors when converting between atoms and mass.

You will need to calculate molar mass of a compound and use Avogadro's number.

Something to consider...

• We have looked at compounds and completed dimensional analysis problems using quantities within the full compound.

• What if you were asked about part of the compound?

• For instance, how many moles of chlorine are there in 47.61g of MgCl₂?

• To answer, first use the molar mass of MgCl₂ to convert to moles of magnesium chloride

• But next, you will need to consider that there are 2 moles of Cl in one moles of MgCl₂

Try it --> Read the question on the next slide. On the slide after that, choose the correct choice that answers the question. Again, be sure to show all work as I will be grading this as well.

Multiple Choice

Choose the correct answer here.

• A

• B

• C

• D

Now let's move onto a new topic, calculating mass percent.

In this topic, we will learn to calculate the percentage of each element within a compound.

Here's what we'll need to do:

• Calculate the total mass of water --> 18.02g/mol

• Now calculate the total mass of hydrogen in the compound --> 2.02g/mol

• Divide part by whole, 2.02/18.02

• Then finish by multiplying by 100!

• You've now calculated the part of water that is hydrogen only.

• The rest, of coursem, is oxygen. So the %H +%O = 100%

• This is only true in this case because the compound is only made up of hydrogen and oxygen.

Multiple Choice

What is the percent of oxygen in carbon dioxide?

• 27.3%

• 100%

• 72.7%

• 16.3%

Multiple Choice

Find the mass percent of hydrogen in carbonic acid.

• 19.3%

• 77.4%

• 1.6%

• 3.3%

Answer the next slide on the multiple choice slide that follows by choosing the correct answer choice from those provided.

Multiple Choice

Choose the correct answer to the previous slide below.

• A

• B

• C

• D

YOUR WORK IS NOW COMPLETE!

SAVE YOUR WORK AND SUBMIT IT FOR GRADING.

THEN UPLOAD ALL WORK THAT YOU'VE DONE ON PAPER TO GOOGLE CLASSROOM.

HAVE A GREAT WEEKEND!