# Question 4.7: Assigning Oxidation Numbers Use the rules from Table 4.5 to ...

Assigning Oxidation Numbers Use the rules from Table 4.5 to obtain the oxidation number of the chlorine atom in each of the following: (a) $HClO_4$ (perchloric acid), (b) $ClO_3^-$ (chlorate ion).

PROBLEM STRATEGY

In each case, write the expression for the sum of the oxidation numbers, equating this to zero for a compound or to the charge for an ion (Rule 6). Now, use Rules 2 to 5 to substitute oxidation numbers for particular atoms, such as -2 for oxygen and +1 for hydrogen, and solve for the unknown oxidation number (Cl in this example).

Table 4.5

 Rules for Assigning Oxidation Numbers Rule Applies to Statement 1 Elements The oxidation number of an atom in an element is zero. 2 Monatomic ions The oxidation number of an atom in a monatomic ion equals the charge on the ion. 3 Oxygen The oxidation number of oxygen is  -2 in most of its compounds. (An exception is O in $H_2O_2$ and other 4 Hydrogen The oxidation number of hydrogen is + 1 in most of its compounds. (The oxidation number of hydrogen is -1 in binary compounds with a metal, such as $CaH_2$.) 5 Halogens The oxidation number of fluorine is  -1 in all of its compounds. Each of the other halogens (Cl, Br, I) has an oxidation number of  -1 in binary compounds, except when the other element is another halogen above it in the periodic table or the other element is oxygen. 6 Compounds and ions The sum of the oxidation numbers of the atoms in a compound is zero. The sum of the oxidation numbers of the atoms in a polyatomic ion equals the charge on the ion.
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Question: 4.9

## Calculating Molarity from Mass and Volume A sample of NaNO3 weighing 0.38 g is placed in a 50.0-mL volumetric flask. The flask is then filled with water to the mark on the neck, dissolving the solid. What is the molarity of the resulting solution? PROBLEM STRATEGY To calculate the molarity, you ...

You find that 0.38 g NaNO_3  is   4.\underl...
Question: 4.3

## Deciding Whether Precipitation Occurs For each of the following, decide whether a precipitation reaction occurs. If it does, write the balanced molecular equation, and then the net ionic equation. If no reaction occurs, write the compounds followed by an arrow and then NR (no reaction). a. Aqueous ...

a. The formulas of the compounds are NaCl and [lat...
Question: 4.2

## Writing Net Ionic Equations Write a net ionic equation for each of the following molecular equations. a. 2HClO4(aq) + Ca(OH)2(aq) → Ca(ClO4)2(aq) + 2H2O(l ) Perchloric acid, HClO4, is a strong electrolyte, forming H^+ and ClO4^- ions in solution. Ca(ClO4)2 is a soluble ionic compound. b. ...

a. According to the solubility rules presented in ...
Question: 4.14

## Calculating the Quantity of Substance in a Titrated Solution A flask contains a solution with an unknown amount of HCl. This solution is titrated with 0.207 M NaOH. It takes 4.47 mL NaOH to complete the reaction. What is the mass of the HCl? PROBLEM STRATEGY You convert the volume of NaOH (4.47 × ...

The calculation is as follows: 4.47  \times...
Question: 4.13

## Calculating the Volume of Reactant Solution Needed Consider the reaction of sulfuric acid, H2SO4, with sodium hydroxide, NaOH. H2SO4(aq) + 2NaOH(aq) → 2H2O(l) + Na2SO4(aq) Suppose a beaker contains 35.0 mL of 0.175 M H2SO4. How many milliliters of 0.250 M NaOH must be added to react completely with ...

The calculation is as follows: 35.0  \times...
Question: 4.12

## Determining the Amount of a Species by Gravimetric Analysis A 1.000-L sample of polluted water was analyzed for lead(II) ion, Pb^2+, by adding an excess of sodium sulfate to it. The mass of lead(II) sulfate that precipitated was 229.8 mg. What is the mass of lead in a liter of the water? Give the ...

Following Example 3.7, you obtain the mass percent...
Question: 4.11

## Diluting a Solution You are given a solution of 14.8 M NH3. How many milliliters of this solution do you require to give 100.0 mL of 1.00 M NH3 when diluted (Figure 4.21)? ...

You know the final volume (100.0 mL), final concen...
Question: 4.10

## Using Molarity as a Conversion Factor An experiment calls for the addition to a reaction vessel of 0.184 g of sodium hydroxide, NaOH, in aqueous solution. How many milliliters of 0.150 M NaOH should be added? PROBLEM STRATEGY You first need to convert grams NaOH to moles NaOH, because molarity ...

Here is the calculation. (The molar mass of NaOH i...
Question: 4.1