Chapter 16, Problem 34CI

(a)

Interpretation Introduction

Interpretation: A strip of magnesium metal dissolves rapidly in 6.00 mL of a 0.150 M HCl solution, producing hydrogen gas and magnesium chloride.

  $\text{Mg}\left(\text{s}\right)\text{ + HCl}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right){\text{ + MgCl}}_{\text{2}}\left(\text{aq}\right)$

Assign oxidation numbers to all of the elements in the reactants and products.

Concept Introduction:Here are the rules for assigning oxidation number to elements:

• For an element in its free state it is assigned an oxidation number of zero.
• Monatomic ions have oxidation number that is equal to charge of the monatomic ion.
• Alkali metals have +1 oxidation number, alkaline earth metals have +2 oxidation number and halogens are assigned -1 oxidation number.
• In most compounds H is assigned a +1 oxidation number and O is assigned a -2 oxidation number.
• For a neutral compound the summation of oxidation numbers of all elements in the compound is zero.

If the oxidation number of an element increases then it undergoes oxidation and if the oxidation number of the element decreases then it undergoes reduction.

(b)

Interpretation Introduction

Interpretation: $\text{Mg}\left(\text{s}\right)\text{ + HCl}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right){\text{ + MgCl}}_{\text{2}}\left(\text{aq}\right)$

To write the balanced chemical equation for the reaction.

Concept Introduction:In a balanced chemical equation for a reaction the number of atoms of each element is equal on both side of the reaction.

(c)

Interpretation Introduction

Interpretation: $\text{Mg}\left(\text{s}\right)\text{ + HCl}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right){\text{ + MgCl}}_{\text{2}}\left(\text{aq}\right)$

To find the oxidizing agent.

Concept Introduction:An oxidizing agent itself gets reduced as it oxidizes other substances. An oxidizing agent accepts electrons.

(d)

Interpretation Introduction

Interpretation: $\text{Mg}\left(\text{s}\right)\text{ + HCl}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right){\text{ + MgCl}}_{\text{2}}\left(\text{aq}\right)$

To find the reducing agent.

Concept Introduction:A reducing agent itself gets oxidized as it reduces other substances. A reducing agent losses electrons.

(e)

Interpretation Introduction

Interpretation: To find the pH of the 0.150 M HCl solution.

Concept Introduction: $\text{pH = - log}\left[{\text{H}}^{\text{+}}\right]$

(f)

Interpretation Introduction

Interpretation: To find the grams of magnesium that can dissolve in the HCl solution.

Concept Introduction: $\text{Molarity = }\frac{\text{moles of solute}}{\text{Liter of solution}}$

  $\text{Moles = }\frac{\text{mass}}{\text{molar mass}}$