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Ch.2 - Atoms & Elements
Chapter 2, Problem 32

Two samples of sodium chloride are decomposed into their constituent elements. One sample produces 6.98 g of sodium and 10.7 g of chlorine, and the other sample produces 11.2 g of sodium and 17.3 g of chlorine. Are these results consistent with the law of definite proportions? Explain your answer.

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1
Identify the law of definite proportions, which states that a chemical compound always contains exactly the same proportion of elements by mass.
Calculate the mass ratio of sodium to chlorine for the first sample: \( \frac{6.98 \, \text{g Na}}{10.7 \, \text{g Cl}} \).
Calculate the mass ratio of sodium to chlorine for the second sample: \( \frac{11.2 \, \text{g Na}}{17.3 \, \text{g Cl}} \).
Compare the two mass ratios calculated in the previous steps to determine if they are the same or very close, which would indicate consistency with the law of definite proportions.
Conclude whether the results are consistent with the law of definite proportions based on the comparison of the mass ratios.

Key Concepts

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

Law of Definite Proportions

The Law of Definite Proportions states that a chemical compound always contains its component elements in fixed ratio by mass, regardless of the amount of the compound or its source. For example, in sodium chloride (NaCl), the ratio of sodium to chlorine by mass should remain constant, typically around 1:1.39, regardless of how the compound is prepared.
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Mass Ratio Calculation

To determine if the results are consistent with the Law of Definite Proportions, one must calculate the mass ratio of sodium to chlorine for each sample. This involves dividing the mass of sodium by the mass of chlorine for both samples and comparing the ratios. If the ratios are equal or very close, the results support the law; if they differ significantly, they do not.
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Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows chemists to predict the amounts of substances consumed and produced in a reaction based on balanced chemical equations. Understanding stoichiometry is essential for analyzing the results of the sodium chloride decomposition in relation to the Law of Definite Proportions.
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