3. Chemical Reactions

Mass Percent

GCSE Science Revision Chemistry "Calculating Percentage by Mass"

Calculate the percentage by mass of oxygen in the following 
compounds: (c) acetaminophen, C8H9NO2

Calculate the percentage by mass of oxygen in the following
compounds: (b) isopropyl alcohol, C3H8O

Determine the percent composition of nitrogen and oxygen with nitrogen dioxide, NO2.

A mixture of FeO and Fe2O3 with a mass of 10.0 g is con-verted to 7.43 g of pure Fe metal. What are the amounts in grams of FeO and Fe2O3 in the original sample?

Calculate the percentage by mass of the indicated element in the
following compounds: (a) hydrogen in methane, CH4, the major
hydrocarbon in natural gas

An aqueous NaCl solution is made using 112 g of NaCl diluted
to a total solution volume of 1.00 L. Calculate the mass percent of the solution. (Assume a density of
1.08 g>mL for the solution.)

A copper wire having a mass of 2.196 g was allowed to react with an excess of sulfur. The excess sulfur was then burned, yielding SO2 gas. The mass of the copper sulfide produced was 2.748 g.
(a) What is the percent composition of copper sulfide?

Most fertilizers consist of nitrogen-containing compounds
such as NH3, CO(NH2)2, NH4NO3, and (NH4)2SO4. Plants use
the nitrogen content in these compounds for protein synthesis. Calculate the mass percent composition of nitrogen in CO(NH2)2.

Calculate the percentage by mass of the indicated element in the 
following compounds: (d) nitrogen in epinephrine, C9H13NO3 , also 
known as adrenalin, a hormone that is important for the fightor- 
flight response

The compound XCl4 contains 75.0% Cl by mass. What is the
element X?

A metal (M) forms a compound with the formula MCl3. If the
compound contains 65.57% Cl by mass, what is the identity of
the metal?

Water softeners often replace calcium ions in hard water with sodium ions. Since sodium compounds are soluble, the presence of sodium ions in water does not cause the white, scaly residues caused by calcium ions. However, calcium is more beneficial to human health than sodium because calcium is a necessary part of the human diet, while high levels of sodium intake are linked to increases in blood pressure. The U.S. Food and Drug Administration (FDA) recommends that adults ingest less than 2.4 g of sodium per day. How many liters of softened water, containing a sodium concentration of 0.050% sodium by mass, would a person have to consume to exceed the FDA recommendation? (Assume a water density of 1.0 g>mL.)

Calculate the percentage by mass of oxygen in the following 
compounds: (f) penicillin, C16H18N2O4S.

Iron in the earth is in the form of iron ore. Common ores include
Fe2O3 (hematite), Fe3O4 (magnetite), and FeCO3 (siderite).
Calculate the mass percent composition of iron for each of
these iron ores. Which ore has the highest iron content?

The mass percent of an element in a compound is the mass of the element (total mass of the element’s atoms in the com-pound) divided by the mass of the compound (total mass of all atoms in the compound) times 100%. What is the mass per-cent of each element in acetaminophen? (See Problem 2.170.)

The nitrogen in sodium nitrate and in ammonium sulfate is
available to plants as fertilizer. Which is the more economical
source of nitrogen, a fertilizer containing 30.0% sodium nitrate
by weight and costing $9.00 per 100 lb or one containing
20.0% ammonium sulfate by weight and costing $8.10 per
100 lb?

Iron metal can be produced from the mineral hematite, Fe2O3, by reaction with carbon. How many kilograms of iron are present in 105 kg of hematite?

Determine the chemical formula of each compound and 
then use it to calculate the mass percent composition of each 
constituent element. 
b. lead(II) phosphate

Li-ion batteries used in automobiles typically use a
LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. (a) Calculate the mass percent lithium in each electrode material.

What is the percent composition by mass of Mn in potas-sium permanganate, KMnO4? (LO 3.10) 
(a) 22.6%
(b) 34.8%
(c) 49.9% 
(d) 54.9%

The total mass must the same after the reaction.

 It depends on the type of rust that is formed. 

 There is not enough information to determine the total mass. 

 According to the law of conservation of mass, matter cannot be created or destroyed. 

 A 70.0-g iron nail combines with 30.0 g of oxygen to form rust.  What is the total mass of the iron nail plus the rust that forms? 

Calculate the mass percent composition of each of the following substances.
(a) Malachite, a copper-containing mineral: Cu2(OH)2CO3

Calculate the mass percent composition of nitrogen in each
nitrogen-containing compound.
c. NO2

(a) Calculate the mass percentage of Na2SO4 in a solution
containing 10.6 g of Na2SO4 in 483 g of water.

 Converting each percentage to a mass, then dividing by the molar mass of each component gives 0.7796 mol Zn, 0.5179 mol P and 2.071 mol O which need to be converted to small whole numbers.  

Zn16P5O10

Zn6P2O4

Zn3P2O8

 Correct use of the percent composition to determine the simplest whole number ratio. 

Zn5P16O33

 An empirical formula may be determined from the simplest whole number mole ratio of each element in the compound. 

The following data were collected when analyzing a compound used in dentistry as a cement to repair teeth: 
50.82% Zn;	16.04% P;	33.14% O 
What is the empirical formula of the compound?

Percent Composition By Mass Part 1

Calculate the mass percent composition of each of the following substances.
(c) Prussian blue, an ink pigment: Fe4[Fe(CN)6]3

Glycine, an amino acid used by organisms to make proteins, 
is represented by the following molecular model. 
(d) Calculate the percent nitrogen by mass in glycine.

Determine the chemical formula of each compound and 
then use it to calculate the mass percent composition of each 
constituent element. 
c. nitrogen triiodide

Phosphorus is obtained primarily from ores containing calcium
phosphate. If a particular ore contains 57.8% calcium phosphate,
what minimum mass of the ore must be processed to obtain
1.00 kg of phosphorus?

Calculate the mass percent composition of carbon in each
carbon-containing compound.
a. CH4

Mass Percent of a Solution Made Easy: How to Calculate Mass % or Make a Specific Concentration

Saline solution used in hospital contains 0.9% sodium chloride
by mass. Calculate the number of grams of sodium chloride
in 0.5 gal of saline solution if the solution has a density of
1.01 g/mL.

Calculating Mass Percent, Part 1 of 2, from Thinkwell Chemistry

When magnesium metal is burned in air (Figure 3.6), two
products are produced. One is magnesium oxide, MgO. The
other is the product of the reaction of Mg with molecular
nitrogen, magnesium nitride. When water is added to magnesium
nitride, it reacts to form magnesium oxide and ammonia
gas. (c) In
an experiment, a piece of magnesium ribbon is burned in air
in a crucible. The mass of the mixture of MgO and magnesium
nitride after burning is 0.470 g. Water is added to the
crucible, further reaction occurs, and the crucible is heated to
dryness until the final product is 0.486 g of MgO. What was
the mass percentage of magnesium nitride in the mixture obtained
after the initial burning?

Calculate the mass percent composition of carbon in each 
carbon-containing compound. 
c. C2H2

The karat scale used to describe gold alloys is based on
mass percentages. (a) If an alloy is formed that is 50 mol%
silver and 50 mol% gold, what is the karat number of the
alloy? Use Figure 12.18 to estimate the color of this alloy.<img src="https://lightcat-files.s3.amazonaws.com/problem_images/58f742ce1d2f5615-1665497830170.jpg" alt="" />

Silver chloride, often used in silver plating, contains 75.27% Ag
by mass. Calculate the mass of silver chloride required to plate
155 mg of pure silver.

Calculate the percentage by mass of the indicated element in the
following compounds: (c) sulphur in magnesium sulphate, MgSO4, a substance used
as a drying agent

A particular brand of beef jerky contains 0.0552% sodium nitrite
by mass and is sold in an 8.00-oz bag. What mass of sodium
does the sodium nitrite contribute to the sodium content of the
bag of beef jerky?

Lead is a toxic metal that affects the central nervous system. A
Pb-contaminated water sample contains 0.0011% Pb by mass.
How much of the water (in mL) contains 150 mg of Pb? (Assume
a density of 1.0 g>mL.)

 This compound does not contain 63.25% by mass nitrogen. 

 Correct, this compound is commonly known as nitrous oxide or "laughing gas". 

either NO2 or N2O4

 Use the formulas given and the formula masses of each to determine the mass percent nitrogen. 

 A nitrogen oxide is 63.65% by mass nitrogen.  The molecular formula could be: 

Determine the chemical formula of each compound and 
then use it to calculate the mass percent composition of each 
constituent element. 
d. cobalt(II) bromide

(b) Hemoglobin, the oxygen-carrying protein in red blood cells,
has four iron atoms per molecule and contains 0.340% iron by
mass. Calculate the molar mass of hemoglobin.

Describe how to prepare each solution from the dry solute and the solvent.
c. 125 g of 1.0% NaNO3 solution by mass

Calculate the percentage by mass of the indicated element in the
following compounds: (b) oxygen in vitamin E, C29H50O2

Calculate the percentage by mass of oxygen in the following
compounds: (a) vanillin, C8H8O3

The karat scale used to describe gold alloys is based on
mass percentages. (b) If an alloy is formed that is 50 mol% copper and 50 mol% gold, what is the karat number of the alloy? What is
the color of this alloy?<img src="https://lightcat-files.s3.amazonaws.com/problem_images/29a290f5fd6fe3de-1665498007656.jpg" alt="" />

Determine the chemical formula of each compound and
then use it to calculate the mass percent composition of each
constituent element.
c. sulfurous acid

Propenoic acid, C3H4O2, is a reactive organic liquid that is
used in the manufacturing of plastics, coatings, and adhesives.
An unlabeled container is thought to contain
this liquid. A 0.275-g sample of the liquid is combusted to
produce 0.102 g of water and 0.374 g carbon dioxide. Is the
unknown liquid propenoic acid? Support your reasoning
with calculations.

Calculate the percentage by mass of the indicated element in the 
following compounds: (e) oxygen in the insect pheromone sulcatol, 
C8H16O

Calculate the percentage of carbon by mass in each of the
compounds represented by the following models:
(a)

A dioxin-contaminated water source contains 0.085% dioxin
by mass. How much dioxin is present in 2.5 L of this water?
Assume a density of 1.00 g>mL.

Pure gold is usually too soft for jewelry, so it is often alloyed
with other metals. How many gold atoms are in an 0.255-
ounce, 18 K gold bracelet? (18 K gold is 75% gold by mass.)

Copper(II) fluoride contains 37.42% F by mass. Calculate the
mass of fluorine (in g) in 55.5 g of copper(II) fluoride.

Urea, a substance commonly used as a fertilizer, has the for-mula CH4N2O. What is its percent composition by mass?

Calculate the mass percent composition of each of the following substances.
(b) Acetaminophen, a headache remedy: C8H9NO2

Calculate the mass percent composition of nitrogen in each
nitrogen-containing compound.
a. N2O

Mass Percent Example

Calculate the mass percent composition of carbon in each 
carbon-containing compound. 
d. C2H5Cl

An aqueous KNO3 solution is made using 72.5 g of KNO3 diluted
to a total solution volume of 2.00 L. Calculate the mass percent of the solution. (Assume a density of
1.05 g>mL for the solution.)

Percent Composition By Mass

The iodide ion is a dietary mineral essential to good nutrition. In countries where potassium iodide is added to salt, iodine deficiency (or goiter) has been almost completely eliminated. The
recommended daily allowance (RDA) for iodine is 150 mg/day. How much potassium iodide (76.45% I) should you consume if you want to meet the RDA?

A compound whose empirical formula is XF3 consists of 65%
F by mass. What is the atomic mass of X?

Calculate the number of moles of solute present in each
of the following aqueous solutions: (c) 124.0 g of a solution 
that is 6.45% glucose 1C6H12O62 by mass.

A metal (M) forms an oxide with the formula M2O. If the oxide
contains 16.99% O by mass, what is the identity of the metal?

A solution is prepared by dissolving 20.2 mL of methanol
(CH3OH) in 100.0 mL of water at 25 °C. The final volume of the
solution is 118 mL. The densities of methanol and water at this
temperature are 0.782 g>mL and 1.00 g>mL, respectively. For
this solution, calculate the concentration in each unit.
c. percent by mass

A compound, Na2Cr2Ox, where x is unknown, is analyzed
and found to contain 39.70% Cr. What is the value of x?

Mass Percent Concept

How To calculate Percentage Mass | Chemical Calculations | Chemistry | FuseSchool

What is the percent composition of cysteine, one of the 20 amino acids commonly found in proteins? (Gray = C, red = O, blue = N, yellow = S, ivory = H.)

Calculate the percentage by mass of the indicated element in the 
following compounds: (f) carbon in sucrose, C12H22O11, the compound that is 
responsible for the sweet taste of table sugar.

Element X, a member of group 5A, forms two chlorides, XCl3 and XCl5. Reaction of an excess of Cl2 with 8.729 g of XCl3 yields 13.233 g of XCl5. What is the atomic weight and the identity of the element X?

Silver nitrate solutions are often used to plate silver onto other
metals. What is the maximum amount of silver (in grams) that
can be plated out of 4.8 L of an AgNO3 solution containing
3.4% Ag by mass? Assume that the density of the solution is
1.01 g>mL.

Calculate the percentage by mass of oxygen in the following
compounds: (e) dioxin, C12H4Cl4O2

Calcium is an essential nutrient in our body. It is important for
bone health. Four common calcium-containing supplements
are calcium carbonate (CaCO3), calcium citrate (Ca3C12H10O14),
calcium gluconate (CaC12H22O14), and calcium lactate
(CaC6H10O6). Rank these calcium supplements in terms of the
mass percentage of calcium they contain.

Based on the following structural formulas, calculate the
percentage of carbon by mass present in each compound:
(a) Benzaldehyde (almond fragrance) 
(b) Vanillin (vanilla flavor) 
c) Isopentyl acetate (banana flavor)

Rubbing alcohol is a 90% (by mass) solution of isopropyl alcohol, C3H8O, in water. How many moles of isopropyl alcohol are in 50.0 g of rubbing alcohol? (LO 13.4)
(a) 45 mol

A sample that weighs 25.12 g contains 6.022 * 10^23 particles. If 25.00% of the total number of particles are argon atoms and 75.00% are another element, what is the chemical identity of the other constituent?

A phosphorus compound that contains 34.00% phosphorus by
mass has the formula X3P2. Identify the element X.

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Freesciencelessons

1. Intro to General Chemistry

2. Atoms & Elements

4. BONUS: Lab Techniques and Procedures

5. BONUS: Mathematical Operations and Functions

6. Chemical Quantities & Aqueous Reactions

7. Gases

8. Thermochemistry

9. Quantum Mechanics

10. Periodic Properties of the Elements

11. Bonding & Molecular Structure

12. Molecular Shapes & Valence Bond Theory

13. Liquids, Solids & Intermolecular Forces

14. Solutions

15. Chemical Kinetics

16. Chemical Equilibrium

17. Acid and Base Equilibrium

18. Aqueous Equilibrium

19. Chemical Thermodynamics

20. Electrochemistry

21. Nuclear Chemistry

22. Organic Chemistry

23. Chemistry of the Nonmetals

24. Transition Metals and Coordination Compounds

[BOOK CHEM] Clutch Version

Empirical Formula

The empirical formula gives the relative number of atoms.&nbsp;

Percent Yield

The Percent Yield determines how successful the product yield is in a chemical reaction.&nbsp;

Molecular Formula

The&nbsp;molecular formula gives the actual number of atoms.

Naming Ionic Compounds

An ionic compound is composed of a positive ion and a negative ion.&nbsp;

Functional Groups in Chemistry

The Functional Group is the portion of a molecule that is responsible for its chemical reactivity.&nbsp;

Naming Molecular Compounds

Molecular Compounds, also known as covalent compounds, contain only non-metals bonded together.&nbsp;

Naming Ionic Hydrates

An Ionic Hydrate is an ionic compound that is linked to at least one molecule of H2O.&nbsp;

Stoichiometry

Stoichiometry deals with the numerical relationship between compounds in a balanced chemical equation.

Writing Ionic Compounds

Determining the charges of a cation and anion are fundamental in Writing Ionic Compounds.

Polyatomic Ions

Polyatomic Ions are groups of multiple elements that possess a charge.

Balancing Chemical Equations

Balancing Chemical Equations is the first step in future chemical calculations.

Limiting Reagent

The Limiting Reagent represents the compound that is totally consumed in the reaction.&nbsp;

Combustion Analysis

Under Combustion Analysis, the empirical formula of a compound is determined through a combustion reaction.&nbsp;

Mass Percent is the percentage of a particular element within a compound.&nbsp;

Combustion Apparatus

A Combustion Apparatus vaporizes a sample into gases to later determine its formula.

Naming Acids

Acids, for the most part, are covalent compounds that begin with a hydrogen.&nbsp;