# Connexions

You are here: Home » Content » General Chemistry I: 03 Mass Percent and Empirical Formulas POGIL

### Recently Viewed

This feature requires Javascript to be enabled.

# General Chemistry I: 03 Mass Percent and Empirical Formulas POGIL

Module by: Jason Ritchie. E-mail the author

Summary: General Chemistry I: 03 Mass Percent and Empirical Formulas POGIL

POGIL Exercise

Mass Percent and Empirical Formulas

 Bowling Balls 5.45 kg 7.27 kg

Model 1: Mass Percent and Composition

 Chemical Formula Structure 3D structure COcarbonmonoxide CO2carbondioxide

Critical Thinking Exercises:

1. Lets say you have two bowling balls, one weighing 5.45 kg, and the other weighing 7.27 kg. What is the total mass of the two bowling balls?
2. What % of the total mass is the 5.45 kg bowling ball?
3. What % of the total mass is the 7.27 kg bowling ball?
4. Show that your last two answers add up to 100%.
5. What is the molecular mass of the Carbon Monoxide (CO) molecule?
6. What % of the total mass of carbon monoxide is the carbon atom?
7. What % of the total mass of carbon monoxide is the oxygen atom?

1. Show that your last two answers add up to 100%.
2. Using a grammatically correct English sentence, describe how to calculate the mass percent of each component in a molecule or compound.
3. What is the molecular mass of the Carbon Dioxide (CO2) molecule?
4. What % of the total mass of carbon dioxide is the carbon atom?
5. What % of the total mass of carbon dioxide are the oxygen atoms?
6. Explain why your answers for Carbon Monoxide and Carbon Dioxide are different.
7. Algebraically rearrange the formula for percentage above to get the “part” alone on one side of the equation.

1. If a person consumes 22 g of Sodium Chloride (NaCl) in one day, and NaCl is 39% Sodium by mass, how many grams of Sodium did this person consume? (Use your equation from the previous problem to solve for the Sodium “part” of the Sodium Chloride “whole”)

Model 2: Chemical Formulas as Conversion Factors

Empirical Formula: the simplest whole number ratio of atoms of each element present in a compound.

1. If you had 1.00 moles of the Chlorofluorocarbon, CCl2F2, how many moles of Carbon (C) atoms would you have? of Chlorine (Cl) atoms? of Fluorine (F) atoms?
2. If you had 25.0 moles of the Chlorofluorocarbon, CCl2F2, how many moles of Carbon (C) atoms would you have? of Chlorine (Cl) atoms? of Fluorine (F) atoms?
3. Write an algebraic equation to describe how you calculated the number of Cl atoms using the terms: “moles of CCl2F2” and “moles of Cl”. (Make sure that your units cancel correctly)
4. Add two terms to your above equation to convert the “moles of CCl2F2” to “grams of CCl2F2” and the “moles of Cl” to “grams of Cl”.
5. If you had 25.00 grams of the Chlorofluorocarbon, CCl2F2, how many grams of Chlorine (Cl) atoms would you have? of Carbon (C) atoms? of Fluorine (F) atoms?
6. Compare the ratios of the (from problem #17) and the (from problem #20).
7. Which of the previous ratios is the same as in problem #16? What does this mean?
8. If we decomposed a sample of water in the laboratory, we might find that it contained 0.857 g of hydrogen and 6.86 g of oxygen. Convert each of these masses to their corresponding number of moles.
9. Calculate the ratio of ? Is this the ratio that you expected for Water (H2O)?
10. A compound containing nitrogen and oxygen was decomposed in the laboratory giving 24.5 grams of oxygen and 70.0 grams of nitrogen. What is the ratio of moles of nitrogen to moles of oxygen?
11. Write the empirical formula of the above compound in the form NxOy.
12. Can a molecule ever contain a fraction of an atom? Therefore, can an empirical formula ever contain a fraction of an atom?

1. Try thinking of your subscripts decimals as fractions, and then find the lowest common denominator to find the formula with the smallest whole number subscripts.

Exercises:

1. Calculate the mass percent of Carbon in the compound C2H5Cl.
2. The American Dental Association recommends that an adult female should consume 3.0 mg of fluoride (F) per day to prevent tooth decay. If you use a toothpaste that contains Sodium Fluoride (NaF), what mass of NaF contains the recommended amount of fluoride?
3. The drug aspirin was determined to be 60.00% Carbon, 4.48 % Hydrogen, and 35.52% Oxygen by mass. Find the empirical formula of aspirin. (Hint: assume you have 100 g of the aspirin).

## Content actions

PDF | EPUB (?)

### What is an EPUB file?

EPUB is an electronic book format that can be read on a variety of mobile devices.

For detailed instructions on how to download this content's EPUB to your specific device, click the "(?)" link.

### Add module to:

My Favorites (?)

'My Favorites' is a special kind of lens which you can use to bookmark modules and collections. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need an account to use 'My Favorites'.

| A lens I own (?)

#### Definition of a lens

##### Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

##### What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

##### Who can create a lens?

Any individual member, a community, or a respected organization.

##### What are tags?

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

| External bookmarks