Chemistry 9th Edition

Published by Cengage Learning
ISBN 10: 1133611095
ISBN 13: 978-1-13361-109-7

Chapter 4 - Types of Chemical Reactions and Solution Stoichiometry - Integrative Problems - Page 188: 143

Answer

Element X is Se or selenium Hydroselenic acid would be the name 0.252 g of $H_2Se$ used

Work Step by Step

Since element $X^{2-}$ has 36 electrons, we know that element X has 34 electrons normally when it has no charge. Hence, the element has 34 protons, which is Selenium. Since $H_2Se$ is a binary acid, we would name it hydroselenic acid. By balancing the equation given in the problem, we know that we need 2 moles of hydroxide ions for 1 mole of acid. To calculate the total moles of hydroxide ions, we multiply the concentration of it by the number of liters used. This gives us $0.175\times 0.0356$, which is 0.00623 moles of hydroxide. We divide this number by 2 to find the moles of acid which gives 0.003115 moles of acid. Multiplying the number of moles of hydroselenic acid by its molar mass, $80.976$, we obtain a total mass of 0.252 g of $H_2Se$.
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