/*! 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 125 A chemist analyzed several porti... [FREE SOLUTION] | 91影视

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Chapter 1: Problem 125

A chemist analyzed several portions taken from different parts of a sample that contained only selenium, Se, and oxygen, \(\mathrm{O}\). She reported the results in the table. Could this sample be a compound of selenium and oxygen? Explain why or why not. $$ \begin{array}{ccc} \hline \text { Portion } & \text { Total Mass }(g) & \text { Mass of Se }(g) \\\ \hline 1 & 1.518 & 1.08 \\ 2 & 2.056 & 1.46 \\ 3 & 1.873 & 1.33 \\ \hline \end{array} $$

Short Answer

Expert verified
Yes, the sample could be a compound because the mass ratios are nearly constant.

Step by step solution

01

Calculate Mass of Oxygen for Each Portion

To determine the mass of oxygen in each portion, subtract the mass of selenium from the total mass for each. For Portion 1: \(1.518 - 1.08 = 0.438\), for Portion 2: \(2.056 - 1.46 = 0.596\), and for Portion 3: \(1.873 - 1.33 = 0.543\).
02

Determine the Mass Ratios

Calculate the ratio of mass of selenium to mass of oxygen for each portion. For Portion 1: \(\frac{1.08}{0.438} = 2.47\), for Portion 2: \(\frac{1.46}{0.596} = 2.45\), and for Portion 3: \(\frac{1.33}{0.543} = 2.45\).
03

Compare the Mass Ratios

Compare the mass ratios. If the ratios are the same or very close, the sample could be a compound because compounds have a fixed ratio of elements. Here, the ratios (2.47, 2.45, 2.45) are very close to each other, suggesting a fixed composition.
04

Conclude Based on Constant Mass Ratio

Since the ratios of selenium to oxygen masses are consistent across portions, the sample could indeed be a compound of selenium and oxygen.

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Key Concepts

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

Compound Identification
Identifying a chemical compound involves understanding whether the elements combine in a fixed and consistent ratio. In this exercise, we have selenium and oxygen, tested across different portions to see if they adhere to a specific pattern. Chemical compounds are characterized by a distinct atomic ratio that does not vary, wherever the compound is analyzed or sampled. This means that if selenium and oxygen form a compound, their ratio is a unique signature that remains perceptible, despite changes in sample size or quantity.
Mass Ratio
The concept of mass ratio in stoichiometry is an essential tool for determining the existence of a compound. It is calculated by dividing the mass of one element by the mass of another element within the substance.
In our example, the calculated mass ratio of selenium to oxygen across the three portions were approximately all around 2.45.
  • Portion 1: \( rac{1.08}{0.438} = 2.47\)
  • Portion 2: \(\frac{1.46}{0.596} = 2.45\)
  • Portion 3: \(\frac{1.33}{0.543}= 2.45\)
These values being very close to each other indicate a possible fixed composition, leading us to suggest a chemical bond between the two elements.
Elemental Analysis
Elemental analysis is a common technique to determine the composition of a chemical substance. This process includes calculating the mass of each element present in a sample.
In this exercise, it involved determining the mass of selenium and then subtracting this from the total mass to find the mass of oxygen for each portion. This allows us to further explore the mass ratio between selenium and oxygen. Through consistent elemental analysis, chemists can confirm or refute the composition and identity of the sample in question, looking for uniform patterns that represent a true chemical compound.
Consistent Composition
Consistent composition is a hallmark of true chemical compounds. According to the law of definite proportions, compounds are made from elements in specific mass ratios that never change. In the case of the selenium and oxygen sample, the consistent mass ratios across portions strongly indicated that their composition was not random.
The close similarity in mass ratios (2.47 for Portion 1 and 2.45 for Portions 2 and 3) suggests that the different parts of the sample maintain a stable, fixed composition. This consistency in composition across all sampled portions strongly supports the hypothesis that the analyzed substance is a compound of selenium and oxygen.

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Most popular questions from this chapter

The element magnesium reacts with the element oxygen to form a white solid compound, magnesium oxide. When a sample of magnesium that weighs \(24.30 \mathrm{~g}\) reacts with oxygen, it is found that the magnesium oxide produced weighs exactly \(40.30 \mathrm{~g}\). (a) Calculate the mass of oxygen in the magnesium oxide. (b) Calculate the mass of magnesium oxide that could be produced from \(40.0 \mathrm{~g}\) magnesium.

Write a chemical formula for each substance and draw a picture of how the nanoscale particles are arranged at room temperature. (a) Iodine, a solid that consists of diatomic molecules (b) Ozone, a gas that consists of triatomic molecules (c) Helium (d) Carbon dioxide

The element chromium forms three different oxides (that contain only chromium and oxygen). The percentage of chromium (number of grams of chromium in \(100 \mathrm{~g}\) oxide) in these compounds is \(52.0 \%, 68.4 \%,\) and \(76.5 \%\). Do these data conform to the law of multiple proportions? Explain why or why not.

Name and give symbols for three transition metals in the fourth period. Look up each of your choices in a dictionary, a book such as The Handbook of Chemistry and Physics, or on the Internet, and make a list of their properties. Also list the uses of each element.

Give a nanoscale interpretation of the fact that at the melting point the density of solid mercury is greater than the density of liquid mercury, and at the boiling point the density of liquid mercury is greater than the density of gaseous mercury.
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