Chemical Reactions and Equations

Chemical Reactions and Equations

1. Balanced Equations and Reaction Types

Complete and balance the following equations, indicating reaction type and state of matter where necessary.

a. Magnesium acetate (aq) + sodium chloride (aq) →

$Mg(C<em>2H</em>3O<em>2)</em>2(aq) + 2NaCl(aq) \rightarrow MgCl<em>2(aq) + 2NaC</em>2H<em>3O</em>2(aq)$

• Reaction Type: Double displacement (metathesis)

b. Copper (II) hydroxide is heated.

$Cu(OH)<em>2(s) \xrightarrow{\Delta} CuO(s) + H</em>2O(g)$

• Reaction Type: Decomposition

c. Solid sodium is added to liquid water.

$2Na(s) + 2H<em>2O(l) \rightarrow 2NaOH(aq) + H</em>2(g)$

• Reaction Type: Single displacement (redox)

d. The complete combustion of CH4.

$CH<em>4(g) + 2O</em>2(g) \rightarrow CO<em>2(g) + 2H</em>2O(g)$

• Reaction Type: Combustion

e. Silver is added to a solution of sodium hydroxide.

No reaction. Silver (Ag) is less reactive than sodium (Na) and will not displace it from sodium hydroxide (NaOH).

$Ag(s) + NaOH(aq) \rightarrow No Reaction$

• Reaction Type: No reaction

f. Potassium carbonate (aq) + iron (III) hydroxide (s).

$3K<em>2CO</em>3(aq) + 2Fe(OH)<em>3(s) \rightarrow 6KOH(aq) + Fe</em>2(CO<em>3)</em>3(s)$

However, iron (III) carbonate $Fe<em>2(CO</em>3)_3$ is unstable in aqueous solution and will decompose to iron (III) hydroxide and carbon dioxide.
So, the net reaction is:

$3K<em>2CO</em>3(aq) + 2Fe(OH)_3(s) \rightarrow No Reaction$

• Reaction Type: Double displacement (but no actual reaction occurs)

2. Balancing Equations

Balance the following equations using any method.

a.

$As<em>2O</em>5 + H<em>2O \rightarrow H</em>3AsO_4$

Balanced:

$As<em>2O</em>5 + 3H<em>2O \rightarrow 2H</em>3AsO_4$

b.

$Ca<em>3(PO</em>4)<em>2 + H</em>2SO<em>4 \rightarrow CaSO</em>4 + Ca(H<em>2PO</em>4)_2$

Balanced:

$Ca<em>3(PO</em>4)<em>2 + 2H</em>2SO<em>4 \rightarrow 2CaSO</em>4 + Ca(H<em>2PO</em>4)_2$

c.

$H<em>2SO</em>4 + B(OH)<em>3 \rightarrow B</em>2(SO<em>4)</em>3 + H_2O$

Balanced:

$3H<em>2SO</em>4 + 2B(OH)<em>3 \rightarrow B</em>2(SO<em>4)</em>3 + 6H_2O$

3. Reaction Coordinate Diagram for an Exothermic Reaction

A reaction coordinate diagram illustrates the energy changes during a chemical reaction. For an exothermic reaction:

• Reactants: Starting point on the left, representing the initial energy of the reactants.
• Products: Ending point on the right, at a lower energy level than the reactants (since energy is released in an exothermic reaction).
• Transition State: The highest energy point on the curve, representing the activated complex.
• Activation Energy (Ea): The energy difference between the reactants and the transition state. $E_a$ determines the rate of the reaction.
• ΔH (Enthalpy Change): The energy difference between the reactants and the products. For an exothermic reaction, \Delta H < 0.

Effect of a Catalyst:

A catalyst lowers the activation energy ($E_a$) by providing an alternative reaction pathway with a lower energy transition state. This speeds up the reaction. On the reaction coordinate diagram, a catalyst would be represented by a curve with a lower peak (transition state) than the uncatalyzed reaction.

Note: Drawing the diagram requires visual representation with labeled axes (Reaction Coordinate vs. Energy) and labeled parts (Reactants, Products, Transition State, Activation Energy, $\Delta$H). The color distinction would visually show the catalyst's effect on lowering the activation energy.