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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 105a

Suppose you have 5.00 g of powdered magnesium metal, 1.00 L of 2.00 M potassium nitrate solution, and 1.00 L of 2.00 M silver nitrate solution. a. Which one of the solutions will react with the magnesium powder?

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1
Identify the possible reactions: Magnesium (Mg) can react with silver nitrate (AgNO_3) to form silver (Ag) and magnesium nitrate (Mg(NO_3)_2).
Write the balanced chemical equation for the reaction: Mg(s) + 2AgNO_3(aq) \rightarrow 2Ag(s) + Mg(NO_3)_2(aq).
Consider the reactivity series: Magnesium is more reactive than silver, which means it can displace silver from its compound.
Evaluate the reaction with potassium nitrate (KNO_3): Magnesium does not react with potassium nitrate because potassium is more reactive than magnesium and cannot be displaced.
Conclude that magnesium will react with silver nitrate solution, not with potassium nitrate solution.

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Key Concepts

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

Reactivity of Metals

The reactivity of metals is determined by their position in the reactivity series, which ranks metals based on their ability to displace other metals from compounds. Magnesium is a highly reactive metal that can displace less reactive metals from their solutions, making it important to identify which solutions contain metals that magnesium can react with.
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Double Displacement Reactions

Double displacement reactions occur when two compounds exchange ions to form new compounds. In this context, when magnesium reacts with a nitrate solution, it can potentially displace the metal cation from the nitrate, leading to the formation of magnesium nitrate and the release of the other metal. Understanding this type of reaction is crucial for predicting the outcomes of the given solutions.
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Solubility Rules

Solubility rules help predict whether a compound will dissolve in water. For example, most nitrates are soluble, which means that potassium nitrate and silver nitrate will dissociate into their respective ions in solution. Knowing the solubility of these compounds is essential for determining if a reaction will occur when magnesium is introduced.
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