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9

SCIENCE Grade 9 Quarter 2 - Module 8

Percentage Composition of a Compound

Name of Learner: ___________________________

Grade & Section: ___________________________

Name of School: ___________________________

1

This module introduces you to the language of Chemistry. The module is

designed to help you find out how Chemist overcome the problems of counting tiny particles of the atoms, molecules and measuring the moles, mass and the

number of particles and their relation to one another. It is difficult to do so because they are very small and numerous to measure the mass of each atom.

However, in real life situations, pieces of matter are quantified by finding

the mass, counting or weighing them using a unit for measuring quantities of matter based on a fixed number of particles called Mole. Like a dozen, a ream or

a case, a mole also represents a certain number of particles. Remember to search for the answer to the following questions:

● How is the percentage composition of a given compound determined? ● How is the mass percentage of an element in a compound determined

from its formula?

After going through this module, you are expected to: ▪ Determine the percentage composition of a compound given its

chemical formula and vice versa (S9MT-IIj-20) Percentage composition of a compound is a ratio of an amount of each

element to the total amount of individual elements in a compound, which is then multiplied with 100 percent. So, the percentage composition of a compound tells the percentage of the mass made up by each element in a compound.

Are you interested to know how much of an element is present in a compound? You can answer this question by determining percentage

composition.

What’s In

Module

8 Percentage Composition of a Compound

What I Need to Know

2

What’s New

Activity # 2: Find My Percentage! Directions: Read and understand the following situations to solve for what is ask in each problem. Write your solutions on the space provided after each word

problem.

Problem # 1: The Toribio Minor National High School Softball team played 25 games and won 15 of them. What percent of the games did they lose?

Note: Problem No 1 is done for you to guide you in answering problem # 2 and 3.

Solution: 25 games

- 15 won 10

10 lose 25

In Problem no. 1, The total number of games played by the team is 25 and the

total number of wins is 15. Thus, the total number of loses is 10. The question is

asking for the percent of not winning the games. To get the percentage, divide the

total number of loses by the total number of games and then, multiply the quotient

by 100% to get the answer of 40%.

Problem # 2: Michelle answered 38 problems on a test correctly out of 50 items. What percent of the total number of items did Michelle answered

incorrectly? (5 points each) Problem # 3: Let us compare it in a classroom situation. You are 50 in your

section with 21 boys and 29 girls. If you will be asked what percent of the class are boys and what percent of the class are boys and what percent are girls, how

are you going to compute for the answer? (5 points each)

What is It

What is Percentage Composition of a Compound?

Percentage composition is calculated from a molecular formula by

dividing the mass of a single element in one mole of a compound by the mass of one mole of the entire compound. The results of these measurements permit the

calculation of the compound’s percent composition, defined as the percentage by mass of each element in the compound.

X 100% = 40 %

The word problems above will help you understand the next topic. Note

that, to determine the percentage, you must divide the portion of the whole by

the whole itself and multiply it by 100.

3

Formula for the computation of percentage composition:

mass of element in the compound

% mass of element =

Using the formula above, let us try to solve the compound which is so

important to all of us, water (H2O). The computation below shows the molar mass of water on how to compute the percentage of Oxygen and Hydrogen in water:

Percent Composition of Water

To find the mass percent composition of the elements in water, H2O. Follow the following steps:

Step 1: Find the mass of the individual atoms.

● Find the molar mass of water by adding up the atomic masses of the elements. Use values from the periodic table:

H is 1.01 grams per mole O is 16.00 grams per mole

Step 2: Find the number of grams of each component make up one

mole of H2O

● Get the molar mass by adding up all the masses of elements in the

compound. The subscript after the hydrogen (H) indicates there are two atoms of hydrogen. There is no subscript after oxygen (O), which means only one atom is present.

H2O

Step 3: Find the mass percent of each atom.

● Divide the mass of each element by the total mass to get the mass percentages. Formula for the computation of percentage composition:

mass of element in the compound

% mass of element =

▪ mass % H = 2.02 x 100% mass % O = 16.00 x 100 %

18.02 18.02

▪ mass % H = 11.21% mass % O =88.79 %

Note that these percentages sum to equal 100.00% when appropriately rounded.

X 100 %

mass of the

compound

1 O atom (16.00g) = 16.00 g

2 H atoms (1.01g) = 2.02g

18.02 g

X 100 %

mass of the

compound

Figure 1

A pie chart is probably one of the most

useful way to help visualize the

composition of water. The segments of

the circle are indicative of the percentage

composition. The mass percentages of

hydrogen and oxygen add up to 100%.

4

What’s More

Activity # 6: Percent Composition of Smarties

Background:

Every compound has a specific ratio of atoms bonded together. This ratio

of atoms can be written as its CHEMICAL FORMULA. In this activity, we are

going to use a package of Smarties® and consider each pack as a specific

compound. You will be counting each atom (different color candy) to determine

its chemical formula. From this information, you will calculate the formula mass

and chemical composition of your “compound”.

Purpose:

● To simulate the construction of a chemical compound and its

chemical formula.

● To determine the formula mass of a compound.

● To determine the percentage composition of a compound.

Materials: Package of Smarties or Nips

Procedure:

1. Obtain a package of Smarties® and count the number of each color in

your pack. Enter in data table.

2. Use the data entered to determine the “compound’s” CHEMICAL

FORMULA. (Use the first letter of the color as its element symbol & be

sure to use the proper subscripts.) Ex. W5Y3G2 etc…

3. If your package does not contain a particular color, DO NOT put it into

the chemical formula.

4. Determine the total masses for each color for the compound. (so if you

have 3 atoms of green times the molar mass given which is 7g the total

mass would be 21g)

5. Use the formula for % composition to determine the percentage

composition of each “atom” (color) in the compound (candy pack). You

must show the math equation for each and remember to round to the

hundreds place!

6. Now “dispose” of your Smarties! Remember to Share!

89%

11%

Percent Composition of Water

Oxygen

Hydrogen

Figure 1

A pie chart is probably one of the most

useful way to help visualize the

composition of water. The segments of

the circle are indicative of the percentage

composition. The mass percentages of

hydrogen and oxygen add up to 100%.

5

Data & Conclusion:

Table 2: Total Mass and Number of Atoms in Smarties Package

Color of Atom # of Atoms

Mass Number

Total Mass of Atom

% Composition Total Mass of atom x 100 Formula

Mass of compound

Red

(R)

12

= _______ %

Orange (O)

11

= _______ %

Yellow (Y)

9

= _______ %

Green (G)

7

= _______ %

Purple

(P)

1 1

= _______ %

White

(W)

32

= _______ %

Total Formula Mass of Compound = ______________

Final CHEMICAL FORMULA =

What I Have Learned

The percentage composition of a compound tells you the percentage of the

mass made up by each element in a compound. Do this activity to apply what

you have learned.

Activity # 4: Fill Me In! Directions: Fill in the blank spaces to complete the table below.

Table 1:

Element # Mole Molar Mass Total Mass Percentage

1.) Al2 (SO4)3

Al 2 26. 98 g 53.96 g 15.8 %

S 1.) 32.07 g 2.) 4.)

O 12 16.00 g 3.) 5.)

2.) NaBr

Na 1 22.99 g 7.) 9.)

Score: ___ / 10

6

Br 6.) 79.90 g 8.) 10.)

Activity # 5: Pair Matching!

Match the chemical compounds in Column A to their corresponding

percent composition in Column B. Choose the letter of the correct pair and write

the letter of your choice before each item.

Column A Column B

___ 1.) Aluminum sulfate A. 26 % Mg, 74 % Cl ___ 2.) Calcium carbonate B. 39% Ca, 20 % P, 41% O

___ 3.) Magnesium chloride C. 40% Ca, 12% C, 48% O ___ 4.) Calcium phosphate D. 3.09%H, 31.61 % P, 27.21% O

___ 5.) Phosphoric acid E. 15.77 % Al, 28.12 % S, 56.11% O

What I Can Do

Directions: Study the word problem below to apply in real life situations the concept you have learned about percent composition. To note, in order to calculate for the percent composition, divide the experimentally derived mass of

each element by the overall mass of the compound, and then convert it to percentage.

Use the formula in computing for the percent composition to solve the following word problems below. Follow the steps found on pages 6 to 7.

Activity # 3: Percentage Composition Calculation

Calculate the following word problems on percentage composition. Show your solutions. (10 points each item).

A. Soil that is already depleted of its nutrients needs fertilizer. One of the nutrients needed to replenish the soil is nitrogen. If you are an

agricultural technician helping a farmer, which among these fertilizers are you going to use? Show your computations to convince the farmer about

your choice. (10 points each)

1. Ammonia – NH3

2. Ammonium sulfate – (NH4)2 SO4

3. Ammonium nitrate – NH4 NO3

Knowledge about percentage composition is useful in choosing the best

fertilizer that gives higher amount of nitrogen and potassium in the soil. Aside

from this, it will help us to be a wise consumer because it is a good basis for

choosing the food product we need to eat based on its content.

Score: ____ / 5

Score: ___ / 30

7

Directions. Choose the letter of the best answer. Write the chosen letter on the space provided before each number. ___ 1.) Aspirin is a compound with the molecular formula C9H8O4. What is its

percent composition?

A. 40 % C, 4.48 % H, 55.52 % O

B. 50 % C, 4.48 % H, 45.52 % O

C. 60 % C, 4.48 % H, 35.52 % O D. 80 % C, 4.48 % H, 15.52 % O

___ 2.) A compound of protein called Serine has an approximate molar mass of

100 g/mole. If the percent composition is as follows, what is the molecular formula of Serine? A. C3 H7 NO3 B. C4 H7 NO3 C. C6 H7 NO3 D. C8 H7 NO3

___ 3.) Find the molecular mass of glucose, which has a molecular formula

(C6 H12 O6)? A. 160.16 B. 180.16 C. 190.16 D. 192.16

___ 4.) Glucose (C6H12O6) is a six-carbon sugar (hexose) which is also known as the blood sugar. It is an energy source that fuels our body. How many percent

of carbon is present in glucose?

A. % C= 19.99 % C. % C= 39.99 %

B. % C= 29.99 % D. % C= 49.99 % C.

___ 5.) Determine the percent composition of calcium carbonate? A. 25 % Ca, 15 % C, 60 % O B. 40 % Ca, 12 % C, 48 % O

C. 40 % Ca, 12 % C, 16 % O D. 57 % Ca, 19 % C, 34 % O

___ 6.) In sodium nitride, what is the percent composition of a given compound?

A. 16.9 % B. 50 % C. 64.6 % D. 83.1 % ___ 7.) A 2.85g sample contains 0.82g magnesium, 0.41 g carbon and 1.62 g

oxygen. What is the percentage composition of an element given? A. Mg = 28.8 %, C= 14.4 %, O= 56.8 %

B. Mg = 28.8 %, C= 14.4 %, O= 56.8 % C. Mg = 28.8 %, C= 14.4 %, O= 56.8 %

D. Mg = 28.8 %, C= 14.4 %, O= 56.8 % ___ 8.) Bicarbonate of soda (sodium hydrogen carbonate) is used in many

commercial preparations. Its formula is NaHCO3. Find the mass percentages (mass %) of Na, H, C, and O in sodium hydrogen carbonate.

A. Na = 25.36 %, H = 1.20 %, C = 16.30 %, O = 57.14 % B. Na = 27.36 %, H = 1.20 %, C = 14.30 %, O = 57.14 %

C. Na = 37.36 %, H = 1.20 %, C = 15.30 %, O = 57.14 % D. Na = 47.36 %, H = 1.20 %, C = 16.30 %, O = 57.14 %

Assessment

Score: ___ / 15

8

___ 9.) The simplest formula for vitamin C is C3H4O3. Experimental data indicates that the molecular mass of vitamin C is about 180. What is the molecular formula of vitamin C?

A. C2H8O6 B.C4H8O6 C. C6H8O6 D. C8H8O6

___ 10.) What is the percent composition of oxygen in the compound of H2O? A. 33. 3% B. 66.6% C. 77. 5 % D. 88.8 %

___ 11.) Which of the following is the percent composition of Carbon monoxide?

A. 21. 49 % B. 49. 20 % C. 50. 00 % D. 57. 12 %

____ 12.) The formula for butane is C2H5 and its molecular mass is about 60.

What is the molecular formula of butane? A. C4H10 C6 H10 C. C6 H12 D. C8 H12

____ 13.) A 24.81 g sample of a gaseous compound containing only carbon, oxygen, and chlorine is determined to contain 3.01 g C,4.00g O, and17.81g Cl.

What is this compound’s percent composition? A. 12.1% C, 26.1% O, 71.8% Cl

B. 12.1% C, 16.1% O, 71.8% Cl C. 12.1% C, 336.1% O, 71.8% Cl D. 16.1% C, 16.1% O, 71.8% Cl

____ 14.) What is the percent composition for each element in Ammonium

sulfide? A. 12 % N, 4 % H, 28 % S

B. 14 % N, 1 % H, 32 % S C. 21 % N, 6 %H, 24 % S D. 28 % N, 8 % H, 64 % S

____ 15.) Identify the % composition of each element in magnesium chloride.

A. 26 % Mg, 74 % Cl C. 46 % Mg, 74 % Cl

B. 36 % Mg, 84 % Cl D. 56 % Mg, 74 % Cl

9

Percent composition plays an important role in everyday lives. Percentages

can be compared more easily than fractions. Shops advertise discounts on

products. These discounts are percentages. Financial institutions quote interest

charged to the client on loans, or interest paid for money invested, as a

percentage.

Perform this activity to utilize practical uses of percentage composition.

Activity 7: It’s Grocery Time! Objectives:

o Apply the concept of percentage composition in choosing grocery

items; and o Realize that the amount of substance intake can be monitored with

the use of percentage composition.

Materials: Grocery item containers or packages (food wrappers, can, bottles etc.)

Procedure: 1. Get three samples of containers or packages of grocery items such as

canned goods, snacks and beverages. 2. List the substances written as contents/ ingredients on the label. Choose

two substances from each type of grocery item.

3. Research from a chemistry book or from the internet the chemical formula of the substances on your list.

4. Compute for the percentage composition of the substances you have listed.

Table 3: Use this table for your answer

List of Substances

Chemical Formula (3 pts.)

Percentage ( 5 pts.)

Canned Goods

1. 2. Snacks

1. 2. Beverages

1. 2.

Guide Questions:

1. Based on this activity, what food do you regularly consume which

gives your body a lot of carbon (C) atoms and sodium (Na) ions?

(5 pts.)

2. Are these good for your body? Why? Research on how much of

these types of food are recommended for your age group. (5 pts.)

Additional Activities

Score: ____ / 60

10

Answer Key-Gr9Q2W8 Science

Assessment

C

A

B

C

C

A

A

B

C

D

D

A

B

C

A

What I have

learned

Activity # 4

Fill Me In

3

96.21 g

192.00 g

28.1 %

56.1 %

1

22.99 %

79.90 %

23.3 %

77.7 %

What I know

Pre- Assessment

A

B

B

D

C

A

D

A

B

B

B

A

C

C

A

What’s In

Bubblegram

Activity # 1

Molecules

Proton

Electron

Element

What’s New

Activity # 2

Find My Percentage 40 %

24 %

42 % boys and

58 % girls

What I Can Do

1.)

ammonia,

NH3 = 82.22 %

ammonium

sulphate -

(NH4)2SO4

24.98% c.) ammonium nitrate,

NH4NO3 = 35.00%

Pair Matching

Activity # 5

1. E 4. B

2.C 5. D

3. A

11

References

Book: Chemistry; Science and technology Textbook for Third Year

Reprint Edition, 2006, 2009, Revised Edition, 2004, First Edition, 1991

Department of Education, Culture and Sports.1992 Teaching Resource

Package: S&T Chemistry. PASME ed August 13, 2020 from

https://www.northpolk.org/Page/1588

Chemistry: Percentage Composition; Retrieved 14, 2020 from http://www.chemistry.wustl.edu/~coursedev/Online%20tutorials/Plink/chemformkey.ht

How to Calculate Percent Composition, Retrieved August14,2020 from

https://www.thoughtco.com/mass-percent-composition-example-

Introduction to Chemistry; Retrieved August 15, 2020 from https://pressbooks.bccampus.ca/chem1114langaracollege/chapter/

Packages of Smarties; Retrieved August 26, 2020 from https://www.google.com/search?q=packages+of+smarties&tbm=isch&source=iu&ictx=1

Percent Composition of Smarties; Retrieved August 24, 2020 from https://www.matsuk12.us/cms/lib/AK01000953/Centricity/Domain/2870/Smartie_P

Thought Co.; Molecular Formula and Simplest Formula Retrieved August 24, 2020 from https://www.thoughtco.com/molecular-and-simplest-formula-problem-609514

Development Team Mi Ultimo Adios

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Majarani M. Jacinto, CESO VI SDS-ZDS

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