Q. 10.23 - An Introduction to General, Organic, and Biological Chemistry

Question

Use Le Châtelier's principle to predict whether each of the following changes causes the system to shift in the direction of products or reactants:

$HN{O}_2\left(aq\right)+H_{2}O\left(l\right)\rightleftarrows CH{O}_2^{-}\left(aq\right)+H_{3}O\left(aq\right)$

a. adding more ${\mathrm{CHO}}_2^{-}$

b. removing some ${\mathrm{HCHO}}_2$

c. removing some ${\mathrm{H}}_3{\mathrm{O}}^{+}$

d. adding more ${\mathrm{HCHO}}_2$

Step-by-Step Solution

Answer

a) when ${\mathrm{CHO}}_2^{-}$ is added it shifts backward or produces more reactants

b) when ${\mathrm{HCHO}}_2$ is removed it shifts backward or produces more reactants

c) when ${\mathrm{H}}_3{\mathrm{O}}^{+}$ is removed it shifts forwards or produces more products.

d) when ${\mathrm{HCHO}}_2$is added it shifts forwards or produces more products.

Step 1: Introduction

Given is the chemical equation 

$$\begin{gathered} HN{O}_2\left(aq\right)+H_{2}O\left(l\right)\rightleftarrows CH{O}_2^{-}\left(aq\right)+H_{3}O\left(aq\right) \\ Reactants Products \end{gathered}$$

To find whether each of the following changes causes the system to shift in the direction of products or reactants using Le Châtelier's principle 

Step 2: explanation of (a)

One of the products is ${\mathrm{CHO}}_2^{-}$ . When ${\mathrm{CHO}}_2^{-}$ is added, the equilibrium shifts to that direction where it is consumed. This means it shifts backward or produces more reactants.

Step 3: explanation of (b)

One of the products is ${\mathrm{HCHO}}_2$ . When ${\mathrm{HCHO}}_2$ is removed, then the equilibrium shifts to that direction where it produces reactants. This means it shifts backward or produces more reactants.

Step 4: explanation of (c)

One of the products is ${\mathrm{H}}_3{\mathrm{O}}^{+}$ . When ${\mathrm{H}}_3{\mathrm{O}}^{+}$ is removed, the equilibrium shifts to that direction Where it produces products. This indicates it advances or generates more goods.

Step 5: explanation of (d)

${\mathrm{HCHO}}_2$ is one of the reactants. When ${\mathrm{HCHO}}_2$ is added, then the equilibrium shifts to that direction where it produces products. This means it shifts forwards or produces more products.