quantitative analysis: 2 - morrison's...

Quantities in Chemistry 123NEL

2.52.5Quantitative Analysis:

Concentrations of SolutionsWhen a driver is asked to breathe into a Breathalyzer, the instrument analyzesthe breath sample and determines the quantity of alcohol in the driver’s blood(Figure 1). A lifeguard at a swimming pool takes a sample of pool water toanalyze the quantity of acid and determine whether any chemicals need to beadded to the pool (Figure 2). Soil samples are sent to a laboratory to beanalyzed for the quantity of toxins. Blood and urine are routinely analyzed inmedical labs to determine the quantities of sugars, ions, gases, and fats theycontain.

High levels of cholesterol in the blood have been linked to heart disease andstroke. The quantity of cholesterol in the blood increases after a meal becausemany foods contain cholesterol. As the cells of the body use cholesterol, itsquantity in the blood decreases to a minimum level. To obtain an accuratemeasurement of the quantity of cholesterol in the blood, a patient is asked tofast for 12 to 14 h before a blood sample is drawn. The patient is also asked tostop taking medications that could affect the cholesterol level.

In many laboratory procedures, such as the cholesterol test, the quantity(usually concentration) of a chemical entity is measured. This type of analysisis called quantitative analysis.

Concentrations of SolutionsIn many cases, quantitative analysis involves the measurement of theconcentration of a solute in a solution. The concentration of a solution is theratio of the quantity of solute to the quantity of solution. In general, theconcentration, c, may be expressed by the ratio

concentration �

A solution is dilute if it has a relatively small quantity of solute per unitvolume of solution (Figure 3(a)). A solution is concentrated if it has arelatively large quantity of solute per unit volume of solution (Figure 3(b)).

quantity of solute��quantity of solution

Figure 1A Breathalyzer provides an on-the-spot quantitative analysis of aperson’s blood-alcohol content bymeasuring the concentration ofalcohol in a sample of exhaled air.

Figure 2 Quantitative analysis requirescareful and precise work. It alsorequires perseverance andopenness to unexpected results.

quantitative analysismeasurement of the quantity of achemical entity

concentration a ratio of thequantity of solute to the quantity ofsolution; symbol c

(a) dilute solution (b) concentrated solution Figure 3

124 Unit 2 NEL

An intravenous (IV) solution is a solution that is injected directly into apatient’s veins. Knowing the concentration of an IV solution is critical in ahospital setting. The label on the container for a typical IV solution shows theconcentration of the solute in the solution (Figure 4). The doctor or nurse iscareful to administer the solution with the correct solute concentration to apatient. Giving an IV solution with the wrong concentration can sometimesbe fatal. If the concentration of an IV solution is too low, for example, redblood cells swell and burst, causing a condition called hemolytic crisis. Inhemolytic crisis, the cells of the body are deprived of nutrients and oxygen.Severe cases of hemolytic crisis can be fatal if not treated quickly.

Percentage ConcentrationThe concentrations of solutions are sometimes expressed as percentages,especially on the labels of consumer products (Figure 5). For example, avinegar label indicating 5% V/V acetic acid means that there are 5 mL of pureacetic acid dissolved in every 100 mL of vinegar solution. The V/V (volume byvolume) notation indicates that two liquids (water and acetic acid) are mixedto make the solution. The first V refers to the volume of solute dissolved in thesolution. The second V refers to the final volume of the solution.

When the solute is a solid, the percentage concentration is followed by W/V(weight by volume). Historically, the W in W/V stood for weight. Today, the Wrefers to the mass of the solid solute that is used to make the solution. The Vrefers to the total volume of solution made.

Simple equations are used to calculate percentage concentrations. Forvolume by volume (V/V) concentrations,

csolution � � 100%

where csolution is the concentration of the solutionvsolute is the volume of solute in the solutionvsolution is the volume of the solution

For weight by volume (W/V) concentrations,


where csolution is the concentration of the solutionmsolute is the mass of solute in the solutionvsolution is the volume of the solution

msolute�vsolution

vsolute�vsolution

Figure 4 The label on this IV solutionindicates that it contains 0.9%sodium chloride.

Figure 5 The concentrations of differentconsumer products depend on theproduct and sometimes the brandname. Concentrations are usuallyexpressed as percentages.


Section 2.5

A photographic “stop bath” contains 160 mL of pure acetic acid,HC2H3O2(l), in 600 mL of solution. What is the V/V percentageconcentration of acetic acid in the stop bath?

Step 1: List Given Values

vHC2H3O2� 160 mL

vsolution � 600 mL

csolution � ?

Step 2: Write Percentage Concentration Equation, Substitute Values, andSolve

Here you need to use the V/V percentage concentration equation:


� � 100%

csolution � 27% V/V

The concentration of the stop bath is 27% V/V.

ExampleA salt solution is formed by mixing 2.80 g of sodium chloride, NaCl(s), in enoughwater to make exactly 250 mL of solution. What is the W/V percentageconcentration of sodium chloride in the salt solution?

Solution

mNaCl � 2.80 g

vsolution � 250 mL

csolution � ?


� � 100%

csolution � 1.1% W/V

The concentration of the salt solution is 1.1% W/V.

2.80 g�250 mL

msolute�vsolution

160 mL�600 mL

vHC2H3O2�vsolution

SAMPLE problem 1Calculating V/V Percentage Concentration

126 Unit 2 NEL

Molar ConcentrationIn laboratory chemistry, the concentration of a solution is more commonlyexpressed as the molar concentration (c). The molar concentration is theamount of solute, in moles, that is dissolved in one litre of solution.

molar concentration �

c �

where c is the molar concentration in mol/Ln is the amount of solute in molv is the volume of solution in L

Molar concentration is sometimes indicated by the use of square brackets.For example, if the molar concentration of an ammonia solution is 0.5 mol/L,it may be written as [NH3(aq)] � 0.5 mol/L.

n�v

amount of solute (mol)��volume of solution (L)

PracticeUnderstanding Concepts1. Gasohol, a solution of ethanol and gasoline, is considered to be a cleaner

fuel than gasoline alone. A typical gasohol mixture, which is available acrossCanada, contains 4.1 L of ethanol in a 55-L tank of fuel. Calculate the V/Vpercentage concentration of ethanol in this mixture.

2. Solder flux, which is available at hardware and craft stores, contains 16 g ofzinc chloride in 500 mL of solution. The solvent is hydrochloric acid. What isthe W/V percentage concentration of zinc chloride in the solution?

3. An IV solution is prepared by dissolving 27.5 g of glucose, C6H12O6(s), in waterto make 550 mL of solution. What is the W/V percentage concentration ofglucose in the IV solution?

Answers

1. 7.5% V/V

2. 3.2% W/V

3. 5.0% W/V

molar concentration theconcentration of a solutionexpressed as moles of solute perunit volume of solution (mol/L)

(a) A sodium hydroxide solution contains 0.186 mol of sodium hydroxidein 0.250 L of solution. Calculate the molar concentration of thesodium hydroxide solution.


nNaOH � 0.186 mol

vNaOH � 0.250 L

cNaOH � ?

SAMPLE problem 2Calculating Molar Concentration of a Solution, Given theAmount of Solute


Section 2.5

Step 2: Write Molar Concentration Equation, Substitute Values, andSolve

cNaOH �

�

cNaOH � 0.744 mol/L

The molar concentration of the sodium hydroxide solution is 0.744 mol/L.

(b) A solution is prepared by dissolving 1.68 g of copper(II) sulfate,CuSO4(s), in enough water to make 150 mL of solution. Calculate themolar concentration of the copper(II) sulfate solution. The molarmass of copper(II) sulfate is 159.6 g/mol.

In section 2.2, you learned that chemists measure the amount of a chemical(number of moles) by mass. Here you are given the mass of solute that isused to prepare a solution, and you need to calculate the concentration ofthe solution.


mCuSO4� 1.68 g

vCuSO4� 150 mL

cCuSO4� ?

Since molar concentration is calculated per litre of solution, convert thegiven volume of solution from millilitres to litres.

vCuSO4� 150 mL �

vCuSO4� 0.150 L

Step 2: Convert Molar Mass of Compound to Amount of CompoundIn this problem, you are given the mass of the solute and the volume of thesolution. To calculate the molar concentration of the solution, you must firstcalculate the amount of copper(II) sulfate in 1.68 g of the salt.

nCuSO4� 1.68 g CuSO4 �

nCuSO4� 0.0105 mol CuSO4

Step 3: Write Molar Concentration Equation, Substitute Values, andSolve

cCuSO4�

�

cCuSO4� 0.0700 mol/L

The molar concentration of the copper(II) sulfate solution is 0.0700 mol/L.

0.0105 mol CuSO4��0.150 L

nCuSO4�vCuSO4

1 mol CuSO4��159.6 g CuSO4

1 L�1000 mL

0.186 mol NaOH��

0.250 L

nNaOH�vNaOH

You can also use the molar concentration equation to calculate the amount(number of moles) of solute in a solution, when you know the concentrationand volume.

128 Unit 2 NEL

ExampleSodium carbonate, Na2CO3(s), is a water softener that is a significant part ofwashing-machine detergent. A student dissolves 5.00 g of solid sodiumcarbonate in enough water to make 250 mL of solution. What is the molarconcentration of the sodium carbonate solution?

Solution

mNa2CO3� 5.00 g

vNa2CO3� 250 mL �

vNa2CO3� 0.250 L

MNa2CO3� 105.99 (calculated from periodic table values)

cNa2CO3� ?

nNa2CO3� 5.00 g Na2CO3 �

nNa2CO3� 0.0472 mol Na2CO3

cNa2CO3�

�

cNa2CO3� 0.189 mol/L

The molar concentration of the sodium carbonate solution is 0.189 mol/L.

0.0472 mol Na2CO3��0.250 L

nNa2CO3�vNa2CO3

1 mol Na2CO3��105.99 g Na2CO3

1 L�1000 mL

PracticeUnderstanding Concepts4. Household bleach is an aqueous solution that contains 5.25 g of sodium

hypochlorite, NaOCl(aq), per 100.0 mL of solution. What is the molarconcentration of sodium hypochlorite in bleach?

5. A brine solution that is used in pickling contains 235 g of pure sodiumchloride, NaCl(s), dissolved in 3.00 L of solution. What is the molarconcentration of the sodium chloride?

6. A stock solution of hydrochloric acid, HCl(aq), is made by dissolving 7.66 g ofhydrogen chloride, HCl(g), in enough distilled water to produce 1.50 L ofsolution. Calculate the concentration of aqueous hydrochloric acid in thisstock solution.

7. Potassium dichromate solution, K2Cr2O7(aq), is used to analyze the alcoholcontent of wine. A lab technician dissolves 102.9 g of solid potassiumdichromate in enough distilled water to produce 1.75 L of aqueous potassiumdichromate. Determine the concentration of aqueous potassium dichromatein this solution.

Answers

4. 0.705 mol/L

5. 1.34 mol/L

6. 0.140 mol/L

7. 0.200 mol/L


Section 2.5

A sample of laboratory ammonia solution, NH3(aq), has a molarconcentration of 14.8 mol/L (Figure 6). What amount of ammonia ispresent in a 1.50-L bottle? (Remember that amount means number ofmoles.)


vNH3� 1.50 L

cNH3� 14.8 mol/L

nNH3� ?

Step 2: Write Molar Concentration Equation

cNH3�

Step 3: Isolate Unknown Value on Left Side of EquationTo calculate the amount of ammonia, isolate the nNH3

term on the left side of theequation.

nNH3� cNH3

vNH3

Step 4: Substitute Values into Equation, and Solve

nNH3� cNH3

vNH3

� � 1.50 L

nNH3� 22.2 mol NH3

There is 22.2 mol of ammonia in the bottle.

ExampleThe concentration of sodium chloride, NaCl(aq), in typical blood serum isapproximately 0.140 mol/L. What amount of sodium chloride is in 0.120 mL ofblood serum?

Solution

vNaCl � 0.120 mL �

vNaCl = 1.20 � 10�4 L

cNaCl � 0.140 mol/L

nNaCl � ?

cNaCl �

nNaCl � cNaClvNaCl

� � 1.20 � 10�4 L

nNaCl � 1.68 � 10�5 mol NaCl

There is 1.68 � 10�5 mol of sodium chloride in the blood serum.

0.140 mol NaCl��

L

nNaCl�vNaCl

1 L�1000 mL

14.8 mol NH3��L

nNH3�vNH3

SAMPLE problem 3Calculating Amount of Solute in a Solution

Figure 6 Aqueous ammonia is purchased forscience laboratories as aconcentrated solution.

130 Unit 2 NEL

The molar concentration equation may be used to calculate the volume of asolution when the concentration and amount of solute are known.

PracticeUnderstanding Concepts8. What amount of silver nitrate, AgNO3(aq), is in 50.0 mL of a 0.570-mol/L

solution?

9. The molar concentration of commercial hydrochloric acid, HCl(aq), is12.4 mol/L. What amount of hydrogen chloride is in 1.50 L of commercialhydrochloric acid?

10. The hemoglobin in red blood cells carries oxygen to body tissues. Whatamount of hemoglobin is in 25.0 mL of a hemoglobin solution with aconcentration of 1.90 � 10�3 mol/L?

11. A lab technician adds 35.8 mL of a 0.0176-mol/L solution of potassiumhydroxide, KOH(aq), to a reaction mixture. What amount of potassiumhydroxide does the technician add to the mixture?

Answers

8. 0.0285 mol

9. 18.6 mol

10. 4.75 � 10�5 mol

11. 6.30 � 10�4 mol

What volume of a 5.0-mol/L glucose solution, C6H12O6(aq), contains2.5 mol of glucose?


cC6H12O6� 5.0 mol/L

nC6H12O6� 2.5 mol

vC6H12O6� ?

Step 2: Write Molar Concentration Equation

cC6H12O6�

Step 3: Isolate Unknown Value on Left Side of EquationTo calculate the volume of solution, isolate the vC6H12O6

term on the left side ofthe equation.

vC6H12O6�


vC6H12O6�

�

vC6H12O6� 0.50 L

Therefore, 0.50 L of 5.0-mol/L glucose solution contains 2.5 mol of glucose.

2.5 mol��5.0 mol/L

nC6H12O6�cC6H12O6

nC6H12O6�cC6H12O6

nC6H12O6�vC6H12O6

SAMPLE problem 4Calculating the Volume of a Solution


Parts per MillionIn environmental studies, very dilute solutions often need to be analyzed.For example, dioxin can be detected in lake water at concentrations as low as3 � 10�6 mol/L. (Dioxin is a toxic pollutant that is produced by theincineration of plastics containing chlorine, and also by processes in the pulpand paper industry.) The human body is so sensitive to dioxin that, even atsuch low concentrations, it poses a health risk. Such low molar concentrationvalues are cumbersome to deal with. Therefore, for very dilute solutions,chemists use parts per million (ppm), parts per billion (ppb), or parts pertrillion (ppt). In general, one part per million of chlorine in a swimming poolcorresponds to 1 g of chlorine in 1000 L of pool water, which is equivalent to1 mg of chlorine per litre of water.

Section 2.5

ExampleWhat volume of a 0.120-mol/L copper(II) sulfate solution, CuSO4(aq), contains0.150 mol of copper(II) sulfate?

Solution

cCuSO4� 0.120 mol/L

nCuSO4� 0.150 mol

vCuSO4� ?

cCuSO4�

vCuSO4�

�

vCuSO4� 1.25 L

Therefore, 1.25 L of copper(II) sulfate solution contains 0.150 mol copper(II)sulfate.

0.150 mol��0.120 mol/L

nCuSO4�cCuSO4

nCuSO4�vCuSO4

PracticeUnderstanding Concepts12. Seawater contains approximately 0.055 mol/L of magnesium chloride,

MgCl2(aq). What volume of seawater contains 4.1 mol of magnesium chloride?

13. What volume of 7.6-mol/L hydrochloric acid, HCl(aq), must be poured into aflask to obtain 0.050 mol of hydrochloric acid?

14. A lab technician must add 1.25 mol of iron chloride, FeCl3(aq), to a flask usinga 6.00-mol/L iron chloride stock solution. How many millilitres of the stocksolution must the technician pour into the flask?

15. How many litres of a 0.0020-mol/L sodium dichromate solution, Na2Cr2O7(aq),contains 5.0 mol of sodium dichromate?

Answers

12. 75 L

13. 6.6 mL

14. 208 mL

15. 2500 L

parts per million concentrationunit that is used for very lowconcentrations; one part solute permillion parts of solution; unit ppm

132 Unit 2 NEL

Concentrations in parts per million (ppm) can be expressed using a varietyof units. When solving a problem, choose the units that match theinformation given in the problem. For aqueous solutions,

1 ppm � 1 g/106 mL

� 1 g/1000 L

1 ppm � 1 mg/L

Parts per Million, Billion, andTrillion1 ppm � approximately 1 drop in a

full bathtub1 ppb � approximately 1 drop in a

full swimming pool1 ppt � approximately 1 drop in

1000 swimming pools

DID YOU KNOW ??

Conversion FactorRemember: 1 g � 1000 mg

LEARNING TIPIn a chemical analysis, 2.2 mg of oxygen was measured in 250 mL ofpond water. What is the concentration of oxygen, in parts per million?


mO2� 2.2 mg

vH2O � 250 mL

cO2� ?

Step 2: Write Percentage Concentration EquationSince you are given a mass and a volume, use the W/V percentage concentrationequation:

cO2�

Step 3: Make Necessary Metric ConversionsSince 1 ppm � 1 mg/L, convert vH2O from millilitres to litres. The mass of oxygenis given in milligrams, so it does not have to be converted.

vH2O � 250 mL H2O �

vH2O � 0.25 L H2O


cO2�

�

� 8.8 mg/L

cO2� 8.8 ppm

The concentration of oxygen is 8.8 ppm.

ExampleThe maximum permitted mass of lead in 1.0 L of public drinking water is 5.0 � 10�5 g. What is this concentration, in parts per million?

Solution

mPb � 5.0 � 10�5 g

vH2O � 1.0 L

2.2 mg O2��0.25 L

mO2�vH2O

1 L H2O��1000 mL H2O

mO2�vH2O

SAMPLE problem 5Calculating Concentration in Parts per Million


Type Equation Units

percentage V/V c � � 100% % V/V

percentage W/V c � � 100% % W/V

very low (number) c � � 100%

molar c � � 100% mol/Lnsolute�vsolution

msolute�vsolution

msolute�vsolution

vsolute�vsolution

Section 2.5

cPb � ?

1 ppm � 1 mg/L

mPb � 5.0 � 10�5 g Pb �

mPb � 0.050 mg Pb

cPb �

�

� 0.05 mg/L

cPb � 0.05 ppm

The maximum permitted concentration of lead in public drinking water is0.05 ppm.

0.05 mg�

1.0 L

mPb�vH2O

1000 mg Pb��

1 g Pb

PracticeUnderstanding Concepts16. Formaldehyde, CH2O(g), is an indoor air pollutant that comes from synthetic

materials and cigarette smoke. A dangerous level of formaldehyde is 3.2 mgin a 500.0-L sample of air. Express this concentration of formaldehyde inparts per million.

17. Copper is an element that is required in very small concentrations in thebodies of all animals. What is the concentration of copper, in parts permillion, if 1.0 L of drinking water contains 3.0 � 10�5 g of copper?

18. Dissolved oxygen in natural water is an important measure of the health ofthe ecosystem. In a chemical analysis of the water from a pond, 350 mL ofwater is found to contain 1.8 mg of dissolved carbon dioxide. What is theconcentration of dissolved carbon dioxide, in parts per million?

Answers

16. 6.4 � 10�3 ppm

17. 0.030 ppm

18. 5.1 ppm

Concentration of a Solution EquationsSUMMARY

mg/L � ppmµg/L � ppbng/L � ppt

134 Unit 2 NEL

Diluting Aqueous SolutionsExperiments sometimes require several concentrations of the same solution. Ifyou begin with a solution of known concentration (called a stock solution),you can prepare a solution of lower concentration by dilution. Diluting a stocksolution is a faster and more accurate way to make lower concentrations of asolution than making different concentrations of the solution from scratch.

Calculating the concentration of a dilute solution is straightforward if youknow the concentration of the original stock solution and the volume ofsolvent added. Adding more solvent does not change the quantity of solute,only its concentration. For example, if water is added to 6% hydrogenperoxide until the total volume is doubled, the concentration becomes one-half the original value, or 3% hydrogen peroxide (Figure 7).

You can calculate this concentration by using the following dilution equation:

civi � cfvf

where ci is the concentration of the initial solutionvi is the volume of the initial solutioncf is the concentration of the final solutionvf is the volume of the final solution

This equation allows you to solve for any one variable if the other threevariables are known.

dilution the process of decreasingthe concentration of a solution byadding more solvent

addwater

3% H2O26% H2O2

Figure 7If water is added to 6% V/Vhydrogen peroxide until the totalvolume is doubled, theconcentration becomes one-half ofthe original concentration, or 3% V/Vhydrogen peroxide.

(a) Calculate the final concentration of a hydrogen peroxide solution ifwater is added to 100 mL of 6% V/V hydrogen peroxide until the totalvolume is 200 mL.


ci � 6% V/V

vi � 100 mL

vf � 200 mL

cf � ?

SAMPLE problem 6Calculations of Diluted Solutions


Section 2.5

Step 2: Write Dilution Equation

civi � cfvf

Step 3: Isolate Unknown Value on Left Side of EquationSince you are asked to determine the concentration of the final solution,isolate cf on the left side of the equation:

cf �


cf �

�

cf � 3%

The final concentration of the diluted solution is 3% V/V hydrogen peroxide.

(b) You are asked to dilute a 2.0-mol/L copper(II) sulfate solution tomake 250 mL of 0.50-mol/L copper(II) sulfate solution. What volumeof 2.0-mol/L copper(II) sulfate should you initially use? Describe thedilution procedure.


ci � 2.0 mol/L

cf � 0.50 mol/L

vf � 250 mL

vi � ?

Step 2: Write Dilution Equation

civi � cfvf

Step 3: Isolate Unknown Value on Left Side of EquationSince you are asked to calculate the initial volume of the solution, isolate vion the left side of the equation:

vi �


vi �

�

vi � 62 mL

Therefore, 62 mL of 2.0-mol/L copper(II) sulfate solution is needed to make250 mL of 0.50-mol/L copper(II) sulfate solution.

(0.50 mol/L)(250 mL)��

2.0 mol/L

cfvf�ci

cfvf�ci

(6%)(100 mL)��

200 mL

civi�vf

civi�vf

136 Unit 2 NEL

Procedure: Since you are asked to make 250 mL of the final solution, you requirea 250-mL volumetric flask. The flask has a graduation mark at the 250-mL level.

1. Place 62 mL of the 2.0-mol/L copper(II) sulfate solution into a 250-mLvolumetric flask (Figure 8(a)).

2. Add distilled water up to the 250-mL mark on the flask (Figure 8(b)).

The volume of the final solution is 250 mL, and its concentration is 0.5-mol/Lcopper(II) sulfate.

3. Place a stopper on the flask, and invert several times to thoroughly mix thecontents.

ExampleWhat volume of 10.0-mol/L sodium hydroxide solution, NaOH(aq), is needed toprepare 250 mL of 0.375-mol/L sodium hydroxide solution?

Solution

ci � 10.0 mol/L

cf � 0.375 mol/L

vf � 250 mL

vi � ?

civi � cfvf

vi �

�

vi � 9.38 mL

Therefore, 9.38 mL of 10.0-mol/L sodium hydroxide solution is needed to make250 mL of 0.375-mol/L sodium hydroxide solution.

(0.375 mol/L)(250 mL)��

10.0 mol/L

cfvf�ci

Figure 8(a)

Figure 8(b)

Diluting SolutionsWhen diluting aqueous solutions,other than acids, begin with thevolume of stock solutioncalculated. Then add water toreach the final volume required.

LEARNING TIP

PracticeUnderstanding Concepts19. Calculate the final concentration of a glucose solution if 240 mL of 15% W/V

glucose is diluted with water to 300.0 mL.

20. A laboratory technician needs to make 500.0 mL of a 0.100-mol/L sulfuricacid solution. What volume of 16.0-mol/L sulfuric acid does the technicianneed to use?

21. How many millilitres of a 14.8-mol/L ammonia solution, NH3(aq), do you needin order to make 100.0 mL of 1.00-mol/L ammonia solution?

22. Calculate the final concentration of a 0.400 mol/L barium chloride solution,BaCl2(aq), when 125 mL of the solution is diluted with distilled water to a finalvolume of 500.0 mL.

Answers

19. 12% W/V glucose

20. 3.13 mL

21. 6.76 mL

22. 0.100 mol/L


Section 2.5

Section 2.5 QuestionsUnderstanding Concepts1. What mass of pure hydrogen peroxide, H2O2(l), is

needed to make 500 bottles that each contain250 mL of 6% W/V hydrogen peroxide?

2. The maximum acceptable concentration of fluorideions in municipal water supplies is 1.5 ppm. What isthe maximum mass of fluoride ions you would getfrom a 250-mL glass of water?

3. How many grams of sucrose, C12H22O11(s), are in50.0 mL of a 0.50-mol/L solution of sucrose in water?

4. What is the molar concentration of phosphoric acidin a solution that contains 40.2 g of hydrogenphosphate, H3PO4(s), in 250 mL of solution?

5. (a) A lab technician dilutes 45.5 mL of a 1.50-mol/Lsodium sulfate solution, Na2SO4(aq), to a finalvolume of 200.0 mL. What is the concentration ofthe diluted solution?

(b) Another lab technician dilutes 50.0 mL of a 3.50-mol/L nitric acid solution, HNO3(aq), to a2.50-mol/L nitric acid solution. What is the finalvolume?

Applying Inquiry Skills6. A lab technician uses a 0.25-mol/L sodium carbonate

stock solution, Na2CO3(aq), to prepare 250 mL of a0.010-mol/L solution.

(a) Calculate the volume of 0.25-mol/L sodiumcarbonate stock solution needed to prepare thediluted solution.

(b) Describe the procedure that the technicianfollows to prepare the solution. Include safetyprecautions.

Making Connections7. Toxicity of substances for animals is usually

expressed by a quantity called LD50. Research theuse of this quantity. What does LD50 mean? What isthe LD50, in ppm, of a substance considered to be“highly toxic” and a substance considered to be“slightly toxic” for mice on the Hodge and Sternerscale? Assume that the substance is taken by mouth.

8. Why is it important for nurses, doctors, andpharmacists to establish common systems forcommunicating the concentration of solutions?Conduct research to find out what systems they use.Create a wall chart that can be used to informmedical workers of the various units that are used foreach system.

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