/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 5 Calculate the mass percentage of... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 11: Problem 5

Calculate the mass percentage of each element in the following organic compounds to four significant figures. (a) methane, \(\mathrm{CH}_{4}(g)\) (b) ethanol, \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(l)\) (c) acetic acid, \(\mathrm{CH}_{3} \mathrm{COOH}(a q)\) (d) benzene, \(\mathrm{C}_{6} \mathrm{H}_{6}(l)\)

Short Answer

Expert verified
(a) C: 74.85%, H: 25.15%; (b) C: 52.13%, H: 13.13%, O: 34.74%; (c) C: 40.00%, H: 6.71%, O: 53.29%; (d) C: 92.26%, H: 7.74%.

Step by step solution

01

Find Molar Mass of Methane

Methane, CH extsubscript{4}, has a molar mass: \( \text{12.01 g/mol for C} + 4 \times \text{1.008 g/mol for H} = 16.042 \text{ g/mol} \).
02

Calculate Mass Percentage for Methane

For Carbon: \( \frac{12.01 \text{ g/mol}}{16.042 \text{ g/mol}} \times 100\% = 74.85\% \). For Hydrogen: \( \frac{4 \times 1.008 \text{ g/mol}}{16.042 \text{ g/mol}} \times 100\% = 25.15\% \).
03

Find Molar Mass of Ethanol

Ethanol, CH extsubscript{3}CH extsubscript{2}OH, has a molar mass: \( 2 \times \text{12.01 g/mol for C} + 6 \times \text{1.008 g/mol for H} + \text{16.00 g/mol for O} = 46.068 \text{ g/mol} \).
04

Calculate Mass Percentage for Ethanol

For Carbon: \( \frac{24.02 \text{ g/mol}}{46.068 \text{ g/mol}} \times 100\% = 52.13\% \). For Hydrogen: \( \frac{6.048 \text{ g/mol}}{46.068 \text{ g/mol}} \times 100\% = 13.13\% \). For Oxygen: \( \frac{16.00 \text{ g/mol}}{46.068 \text{ g/mol}} \times 100\% = 34.74\% \).
05

Find Molar Mass of Acetic Acid

Acetic acid, CH extsubscript{3}COOH, has a molar mass: \( 2 \times \text{12.01 g/mol for C} + 4 \times \text{1.008 g/mol for H} + 2 \times \text{16.00 g/mol for O} = 60.052 \text{ g/mol} \).
06

Calculate Mass Percentage for Acetic Acid

For Carbon: \( \frac{24.02 \text{ g/mol}}{60.052 \text{ g/mol}} \times 100\% = 40.00\% \). For Hydrogen: \( \frac{4.032 \text{ g/mol}}{60.052 \text{ g/mol}} \times 100\% = 6.71\% \). For Oxygen: \( \frac{32.00 \text{ g/mol}}{60.052 \text{ g/mol}} \times 100\% = 53.29\% \).
07

Find Molar Mass of Benzene

Benzene, C extsubscript{6}H extsubscript{6}, has a molar mass: \( 6 \times \text{12.01 g/mol for C} + 6 \times \text{1.008 g/mol for H} = 78.114 \text{ g/mol} \).
08

Calculate Mass Percentage for Benzene

For Carbon: \( \frac{72.06 \text{ g/mol}}{78.114 \text{ g/mol}} \times 100\% = 92.26\% \). For Hydrogen: \( \frac{6.048 \text{ g/mol}}{78.114 \text{ g/mol}} \times 100\% = 7.74\% \).

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Mass Percentage
Mass percentage is a way of expressing the concentration of an element in a compound. It indicates how much of a compound's mass is due to a specific element. To calculate mass percentage, use the formula:
  • Identify the molar mass of the compound.
  • Determine the molar mass of each element.
  • Divide the element's molar mass by the total molar mass of the compound.
  • Multiply the result by 100 to convert it into a percentage.
For example, the mass percentage of carbon in methane (CH鈧�) is calculated as follows:\[\frac{12.01 \, \text{g/mol}}{16.042 \, \text{g/mol}} \times 100\% = 74.85\%\]Breaking down such calculations can help understand the contribution of each element to the compound's mass.
Organic Compounds
Organic compounds primarily contain carbon and hydrogen atoms bonded together. These compounds are part of a large class that also includes other elements like oxygen, nitrogen, and sulfur. Common features include:
  • Presence of carbon-hydrogen bonds.
  • Often have a complex structure with chains, rings, and various functional groups like OH (hydroxyl) in ethanol (CH鈧僀H鈧侽H).
  • Examples of simple organic compounds include methane ( CH鈧� ) and benzene ( C鈧咹鈧� ).
Understanding organic compounds helps in the study of chemical reactions, biological processes, and the chemical composition of living organisms, highlighting their versatility and significance in chemistry.
Chemical Composition
Chemical composition refers to the identity and ratio of elements that make up a compound. It provides insight into the arrangement of atoms and their presence by weight. To analyze the chemical composition:
  • Calculate the total molar mass of the compound, which is the sum of all atoms' molar masses.
  • Determine each element's contribution to the compound's molar mass.
  • Use these individual contributions to find mass percentages, revealing the weight ratio of elements.
For example, in ethanol ( CH鈧� CH鈧� OH), carbon, hydrogen, and oxygen in the ratio of 2:6:1 create distinct contributions to the compound's properties and reactions.
Significant Figures
Significant figures in chemistry are crucial for precision and accuracy in calculations. They represent the digits in a number that contribute to its measurement accuracy.
  • Ensure that calculations are recorded with the correct number of significant figures.
  • For example, during mass percent calculation, express each percentage to four significant figures, maintaining precision.
  • Rules include:
    • Non-zero digits are always significant.
    • Any zero between significant digits is significant.
    • Leading zeros are not significant.
    • Trailing zeros in a number with a decimal point are significant.
Precision in significant figures ensures that even small variations in chemical measurements remain accurate, providing better data for scientific analysis.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Calculate the mass percentage of each element in each of the following compounds to four significant figures. (a) methanol, \(\mathrm{CH}_{3} \mathrm{OH}(l)\) (b) water, \(\mathrm{H}_{2} \mathrm{O}(l)\)

II - 49. Potassium nitrate is widely used as a fertilizer because it provides two essential elements, potassium and nitrogen. It is made by mixing potassium chloride and nitric acid in the presence of oxygen according to the equation $$ \begin{array}{r} 4 \mathrm{KCl}(a q)+4 \mathrm{HNO}_{3}(a q)+\mathrm{O}_{2}(g) \rightarrow \\ 4 \mathrm{KNO}_{3}(a q)+2 \mathrm{Cl}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l) \end{array} $$ How many kilograms of potassium nitrate will be produced from a solution containing \(50.0\) kilograms of potassium chloride and one containing \(50.0 \mathrm{ki}-\) lograms of nitric acid? An important by-product is chlorine. How many kilograms of chlorine gas will be produced?

When calcium carbonate is added to hydrochloric acid, calcium chloride, carbon dioxide, and water are produced. (a) Write the balanced chemical equation for this reaction. (b) How many grams of calcium chloride will be produced when \(25.0\) grams of calcium carbonate are combined with \(15.0\) grams of hydrochloric acid? (c) Which reactant is in excess and how many grams of this reactant will remain after the reaction is complete?

An ore is analyzed for its lead content as follows. A sample is dissolved in water; then sodium sulfate is added to precipitate the lead as lead(II) sulfate, \(\mathrm{PbSO}_{4}(s) .\) The net ionic equation for the reaction is $$ \mathrm{Pb}^{2+}(a q)+\mathrm{SO}_{4}^{2-}(a q) \rightarrow \mathrm{PbSO}_{4}(s) $$ It was found that \(13.73\) grams of lead(II) sulfate were precipitated from a sample of ore having a mass of \(53.92\) grams. How many grams of lead are there in the sample? What is the mass percentage of lead in the ore?

II-88. A police forensics lab is analyzing a sample of white powder found at a crime scene to determine if it is cocaine. Elemental analysis of the powder shows that it is \(67.31 \%\) carbon, \(6.978 \%\) hydrogen, \(4.618 \%\) nitrogen, and \(21.10 \%\) oxygen by mass. The chemical formula of cocaine is \(\mathrm{C}_{17} \mathrm{H}_{21} \mathrm{NO}_{4} .\) From this evidence, can the investigators conclude that the white powder is cocaine?
See all solutions

Recommended explanations on Chemistry Textbooks

Making Measurements

Read Explanation

Organic Chemistry

Read Explanation

Chemical Analysis

Read Explanation

Chemistry Branches

Read Explanation

Nuclear Chemistry

Read Explanation

Chemical Reactions

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.