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Ch.3 - Mass Relationships in Chemical Reactions
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.3 - Mass Relationships in Chemical ReactionsProblem 87a
Chapter 3, Problem 87a

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

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1
Identify the chemical formula of malachite: Cu_2(OH)_2CO_3.
Calculate the molar mass of each element in the compound: Cu, O, H, and C.
Determine the total molar mass of the compound by summing the molar masses of all atoms in the formula.
Calculate the mass percent of each element by dividing the total mass of each element in the formula by the total molar mass of the compound and multiplying by 100%.
Express the mass percent composition for each element in the compound.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To calculate the molar mass of a compound, you sum the atomic masses of all the atoms in its chemical formula. For malachite, Cu₂(OH)₂CO₃, you would calculate the molar mass by adding the contributions from copper (Cu), oxygen (O), hydrogen (H), and carbon (C) based on their respective quantities in the formula.
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Mass Percent Composition

Mass percent composition refers to the percentage by mass of each element in a compound. It is calculated by dividing the mass of each element in one mole of the compound by the total molar mass of the compound, then multiplying by 100. This concept is essential for understanding the distribution of elements within a compound and is particularly useful in stoichiometry and chemical analysis.
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Chemical Formula Interpretation

Interpreting a chemical formula involves understanding the types and numbers of atoms present in a compound. In the case of malachite, Cu₂(OH)₂CO₃, the formula indicates that there are two copper atoms, two hydroxide groups (OH), one carbonate group (CO₃), and the associated oxygen and hydrogen atoms. This interpretation is crucial for accurately calculating both the molar mass and the mass percent composition of the compound.
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Related Practice
Textbook Question

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

Textbook Question

Sodium borohydride, NaBH4, a substance used in the synthesis of many pharmaceutical agents, can be prepared by reaction of NaH with B2H6 according to the equation 2 NaH + B2H6 → 2 NaBH4

(b) Which reactant is limiting, and how many grams of the excess reactant will be left over?

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

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

Textbook Question

Sodium borohydride, NaBH4, a substance used in the synthesis of many pharmaceutical agents, can be prepared by reaction of NaH with B2H6 according to the equation 2 NaH + B2H6 → 2 NaBH4

(a) How many grams of NaBH4 can be prepared by reaction between 8.55 g of NaH and 6.75 g of B2H6?

Textbook Question

What are the empirical formulas of substances with the following mass percent compositions? (a) Aspirin: 4.48% H, 60.00% C, 35.52% O