Problem 20 - Chemistry: Principles and Reactions

Question

Complete and balance the following equations. If no reaction occurs, write NR. (a) \(\mathrm{Cl}_{2}(g)+\mathrm{Br}^{-}(a q) \longrightarrow\) (b) \(\mathrm{I}_{2}(s)+\mathrm{Cl}^{-}(a q) \longrightarrow\) (c) \(\mathrm{I}_{2}(s)+\mathrm{Br}^{-}(a q) \longrightarrow\) (d) \(\mathrm{Br}_{2}(l)+\mathrm{Cl}^{-}(a q) \longrightarrow\)

Step-by-Step Solution

Answer

Answer: Only the first reaction occurs, involving Cl2 and Br-, and its balanced equation is: $\mathrm{Cl}_{2}(g) + 2\mathrm{Br}^{-}(a q) \longrightarrow 2\mathrm{Br}(g) + 2\mathrm{Cl}^{-}(a q)$.

Step 1: Identify the redux reaction

In this reaction, Cl2 is a stronger oxidizing agent than Br- which means this reaction will occur.

Step 2: Write the balanced equation

The balanced equation for the reaction is: $$ \mathrm{Cl}_{2}(g) + 2\mathrm{Br}^{-}(a q) \longrightarrow 2\mathrm{Br}(g) + 2\mathrm{Cl}^{-}(a q) $$ (b) \(\mathrm{I}_{2}(s)+\mathrm{Cl}^{-}(a q) \longrightarrow\)

Step 1: Check if a redux reaction occurs

In this reaction, I2 is not a stronger oxidizing agent than Cl- which means no reaction will occur.

Step 2: Write NR for no reaction

So the answer for this reaction is: $$ \mathrm{I}_{2}(s)+\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{NR} $$ (c) \(\mathrm{I}_{2}(s)+\mathrm{Br}^{-}(a q) \longrightarrow\)

Step 1: Check if a redux reaction occurs

In this reaction, I2 is not a stronger oxidizing agent than Br- which means no reaction will occur.

Step 2: Write NR for no reaction

So the answer for this reaction is: $$ \mathrm{I}_{2}(s)+\mathrm{Br}^{-}(a q) \longrightarrow \mathrm{NR} $$ (d) \(\mathrm{Br}_{2}(l)+\mathrm{Cl}^{-}(a q) \longrightarrow\)

Step 1: Check if a redux reaction occurs

In this reaction, Br2 is not a stronger oxidizing agent than Cl- which means no reaction will occur.

Step 2: Write NR for no reaction

So the answer for this reaction is: $$ \mathrm{Br}_{2}(l)+\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{NR} $$

Key Concepts

Redox Reactions

Understanding redox reactions is essential when exploring the world of chemistry. Redox is short for 'reduction-oxidation.' It's a type of chemical reaction involving the transfer of electrons between two species. An oxidation reaction involves the loss of electrons, while reduction involves the gain of electrons.

In a redox process, you can identify the species getting oxidized and the one getting reduced by following the transfer of electrons. An easy way to remember this is the mnemonic 'OIL RIG'—Oxidation Is Loss, Reduction Is Gain. Let's look at an example:

• Oxidation: ē ē ē Ē Ē Ē Ē Ē Ē Ē Ē Ē Ē Ē Ē Ē Ē Ē Ē Ē

  Chemical Reaction Predictability

  
  To appreciate the predictability of chemical reactions, you must recognize the patterns that determine whether a reaction will take place. Predictability in chemistry is centered around the reactivity of various substances and knowing the conditions under which they react.The predictability of a reaction can often be determined by looking at reactant characteristics and using established rules like the activity series of metals, which ranks metals based on their ability to be oxidized. A more reactive metal will often displace a less reactive metal from its compounds. Solutions that focus on reaction predictability often stress understanding of these trends and using these principles to deduce outcomes, as well as remembering exceptions to the rules, such as noble gases which typically are unreactive.
  
  Consider this example:
  • In the exercise above, Cl₂ is a stronger oxidizing agent than Br^-, which aids in predicting the first reaction.
  • For the second and third reactions, based on reactivity, I₂ does not displace Cl^- or Br^-, leading to a prediction of no reaction.
  The ability to predict chemical reactions can help in many practical applications, ranging from industrial synthesis to environmental chemistry, providing scientists and students with an essential tool in their chemistry toolkit.