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Ch.22 - The Main Group Elements
Chapter 22, Problem 23

The following pictures represent structures of the hydrides of four second-row elements:
(1)
(2)
(3)
(4)
(c) Which compounds yield H2 gas when they are mixed together?

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1
Identify the second-row elements that form hydrides. These elements are lithium (Li), beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), and fluorine (F).
Determine which of these hydrides can react with each other to produce hydrogen gas (H2).
Consider the typical reactions of these hydrides. For example, metal hydrides like lithium hydride (LiH) can react with water to produce hydrogen gas.
Evaluate the possible reactions between the given hydrides. For instance, a metal hydride reacting with an acid or water could yield H2 gas.
Conclude which specific pairs of hydrides, when mixed, would result in the production of H2 gas based on their chemical properties and typical reactions.

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Key Concepts

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

Hydrides

Hydrides are compounds formed between hydrogen and another element. In the context of second-row elements, these hydrides can exhibit varying properties based on the electronegativity and atomic size of the elements involved. Understanding the nature of these hydrides is crucial for predicting their reactivity and the types of reactions they may undergo, including the production of hydrogen gas.
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Reaction Types

Chemical reactions can be classified into several types, including synthesis, decomposition, and displacement reactions. In the case of hydrides, certain combinations can lead to reactions that produce hydrogen gas (H2) as a byproduct. Recognizing the specific reaction type that occurs when mixing different hydrides is essential for determining which compounds will yield H2 gas.
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Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions. It involves understanding the mole ratios of the substances involved, which is vital for predicting the amounts of products formed, such as H2 gas. By applying stoichiometric principles, one can determine whether the mixing of specific hydrides will result in the generation of hydrogen gas and in what quantities.
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