Solutions Problem Set 20XX

1. Complete the following table.

Name Formula Cation Anion High or low

solubility and phase (s or aq)

sodium chloride NaCl Na+ Cl–

lithium iodide

Mg(ClO3)2

strontium hydroxide

BaCO3

2. Complete the following table.

Name Formula High or low

solubility and phase (s or aq)? Al(OH)3

ammonium chloride

K2S

molybdenum chlorate

Pb(CH3COO)2

copper(II) iodide

CuI calcium sulfite

Ba3(PO4)2 (s)

palladium(II) bromide

Explanation of solution and solubility

A. Solutions generally have 2 important physical characteristics : their ability to conduct an electric current ( electrolytic ) [ non-electrolytes do not conduct electricity ] and their activity on litmus paper

a. Electrolyte and non-electrolyte :

The solution’s ability to conduct electricity is because the solute dissolved had dissociated in water and ions exist in solution. A solution must have ions to conduct electricity.

e.g. NaCl(aq) can conduct electricity because NaCl(s) - - > Na+(aq) + Cl-(aq)

C12H22O11(s) can not conduct because it can not dissociate into ions

 Only soluble ionic compounds and strong acid dissociate to form electrolytes, solutions that conduct electricity

 Molecular compounds and elements can not dissociate when dissolved

( note : weak acids are assumed to remain undissociated and in their molecular form) b. Change color of litmus paper :

Acidic and basic solutions can act on litmus paper because of the presence of hydrogen ions ( H+ (aq) )

and hydroxide ions ( OH-(aq) ) in solution. If a solution have H+ ions, it will change litmus red,

low pH etc.

If a solution have OH- ions, it will change litmus paper blue, taste bitter etc

Characteristics of solutions :

There are four kinds of solutions. They are neutral ionic, neutral molecular, acid and base. a. Neutral ionic solutions : ionic compounds are dissolved in water to make a solution e.g NaCl(aq) , Mg(NO3)2(aq)

Physical characteristics : electrolyte and no activity on litmus paper

b. Neutral molecular solutions : molecular compounds are dissolved in water to make a solution. e.g. C12H22O11(aq) , C2H5OH(aq)

Physical characteristics : non-electrolyte and no activity on litmus paper

c. Acidic solutions : hydrogen compounds are dissolved in water to make a solution e.g. HCl(aq) , H2CO3(aq)

Physical characteristics : electrolyte, taste sour, litmus turns red, low pH, reacts with metal to form gas , neutralize bases

3. Write the balanced dissociation equation for the following ionic compounds: ALL DISSOCIATON EQUATIONS MUST BE BALANCED BY AMOUNTS AND CHARGE!

a. Potassium borate

b. Strontium hydroxide

c. Aluminum carbonate

d. Iron (III) acetate

e. Mercury (II) acetate

f. Lead (II) bromide

g. Aluminum nitrate

h. Vanadium oxalate

i. Ammonium bisulfate

j. Titanium (IV) chlorate

4. What is the difference between an electrolyte and non-electrolyte?

6. Identify the major species of chemical existing in the beaker by writing it/ them into beaker ( list major species present in solution )

NaCl(s) is stirred into water

PbSO4(s) is stirred into water

C25H52(s) is stirred into water CH3OH(l) is stirred

into water

Cl2(g) is stirred into water

Cu(s) is stirred into water

AgOH(s) is stirred into water NaOH(s) is stirred

into water

H3PO4(s) is stirred into water HCl(g) is stirred

7. Identify the significant forms of the substances present in water for the each of the following:

a. Zinc

b. Sodium bromide c. Oxygen

d. Nitric acid e. Methanol f. Sulfur

g. Silver chloride

h. Paraffin wax (C25H52 (s))

1. General definitions :

All solutions are uniform mixtures of a solute and a solvent . ( e.g. mixtures of gases, liquids or solids dissolved in liquids and many alloys which are metal solutions of two or more metals ) a solute can be defined as the substance being dissolved

a solvent can be defined as the substance dissolving the solute. e.g. NaCl(aq) , O2 ( N2 )

Solutions can be described quantitatively;

a. Concentration is the amount of solute ( moles ) dissolved in a specific amount of solvent. ( units such as mol

L , , mole percent , mass fraction , mass - volume fraction , parts per million . etc )

mol kg

b. Solubility is the maximum concentration of solution in units of g_L at a particular temperature c. Molar solubility is the maximum concentration in mol

L at a particular temperature.

Solutions can be described qualitatively,

a. A dilute solution has a small amount of solute dissolved in the solvent. b. A concentrated solution has a large amount of solute dissolved.

c. A saturated solution has the maximum amount of solute dissolved in the solvent at a specific temp.

d. A supersaturated solution has more than the maximum amount of solute dissolved at

Notation for solution

2. Solution process. The general rule :

a. All gases dissolve in each other in all proportions.

b. For solutions, “ like dissolves like “ , meaning the solute will dissolve in a solvent of similar characteristics but not in a solvent of different characteristics.

The dissolving process for solution requires three major steps :

a. The solute particles are separated so that the solvent can fit in between them

( energy is required to break attractions between solute molecules : endothermic step ) b. The solvent particles are separated so that solute can fit between them

( energy is required to break attractions between solvent molecules : endothermic step ) c. The separated solute and solvent particles are combined to form the solution

( energy is released when new attractions are formed : exothermic step )

If step C releases more energy than required in A and B, the solvent will dissolve the solute and an increase in temperature is observed.

If step C releases less energy than required in A and B, external energy is required

( some of the shortfall of energy can be accounted for by the increase of randomness or entropy )

Solution Chemistry : Concentration units

Concentration of solutions is a value ( number ) derived by comparing an amount of solute dissolved in an amount of solvent.

Units of concentration such as molarity, molality, normality, % by volume, % by weight, parts per million, parts per billion. Etc are used in many discipline of Science.

For the Chemistry 20 program, we will only examine a few of these units and will only emphasize molarity.

1. Molarity ( M )

2. % by volume ( % V/V ) 3. % by weight ( % W/V ) 4. ppm ( parts per million )

1. Molarity is defined as the amount of moles of solute dissolved to make 1 L volume of solution

A 1 molar solution means that 1 mol of solute was dissolved in water to make 1 L of solution [ note : it does not mean 1 mol of solute was dissolved into 1 L of solvent ]

A 2 molar solution means 2 mol of solute was dissolved in water to make 1 L of solution 2. % by volume ( % V/V )

A 5% by volume solution means 5 mL of solute was dissolved to make 100 mL of solution A 10% by volume solution means 10 mL of solute was dissolved to make 100 mL of solution 3. % by weight ( % W/V )

A 5% by weight solution means that 5 g of solute was dissolved to make 100 mL of solution A 10% by weight solution means that 10 g of solute was dissolved to make 100 mL of solution

solution of amount solute of amount ion Concentrat  L mol molarity of

unit 

solution of volume solute of mol Molarity 

solution of volume solute of volume by volume

%  x 100%

solution of volume solute of mass by weight

4. % by weight ( % W/W )

Do not forget that the mass of solution contains the mass of solute and solvent

5. Parts per million ( ppm )

Used to describe very dilute solutions. e.g. in the measurement of toxic substances in our environment. Such as measurement of chlorine in swimming pool.

The formula for ppm is

For water and dilute solutions we assume the density is 1g/mL. This means that 1 gram of solution occupies 1 mL and 1mL of water or dilute solution weighs 1 g. Thusly 1kg of water or solution occupies 1L.

THE GENERIC FORMULA FOR CONCENTRATiON is

And the symbol for concentration is ….

solution of mass solute of mass by weight

%  x 100%

8. Calculate the molar concentration, or molarity, of each of the following solutions: a. 2.92 g of table salt in 500 mL of solution

b. 9.22 g of copper (II) sulfate in 250 mL of solution

c. 1.07 g of sodium sulfate in 300 mL of solution

d. 19.5 mg of mercury (II) acetate in 25 mL of solution.

e. 13.71 g of barium hydroxide in 4.0 liters of solution.

9. Calculate the mass of solute in the following quantities and concentrations of solutions? a. 3.00 liters of 14.6 mol/L of HCl (aq)

b. 25.0 mL of 0.0080 mol/L of KMnO4 (aq)

d. 1.50 L of 17.8 mol/L of sulfuric acid

10. Calculate the concentration, in molarity, of each of the following solutions: a. 1.0 mol of KCl in 750 mL of solution

b. 0.50 mol of MgCl2 in 1.5 L of solution

c. 400 g of CuSO4 in 4.00 L of solution

11. Calculate the number of moles and the number of grams of solute in each solution a. 1.0 L of a 0.50 mol/L NaCl solution

b. 500 mL of a 2.0 mol/L KNO3 solution

c. 250 mL of a 0.10 mol/L CaCl2 solution

d. 2.0 L of a 0.30 mol/L Na2SO4 solution

12. What are the ion concentrations of the following solutions (provide dissociation equation to accompany each of your answers).

a. 2.50 mol/L of hydrochloric acid

b. 1.11 mol/L of potassium phosphate

c. 3.60 mmol/L of ammonium dichromate

d. 1.02 mmol/L of cesium dihydrogen phosphate

e. 1.02 mmol/L of aluminum nitrate

f. 2.32 g of platinum (IV) nitrate in 150 mL.

Solutions Problems - Percent Concentration, PPM and Molar Concentrations 1. Calculate the number of grams of solute required to make the following:

a. 2.5 L of normal saline solution (0.90% m/v)

b. 50 mL of 4.0% MgCl2 (m/v)

c. 250 mL of 0.10% MgSO4 (m/v)

2. What is the concentration in percent (m/v) of the following solutions? a. 20 g KCl in 600 mL of solution

b. 32 g NaNO3 in 2.0 L of solution

3. Express the following solutions as % concentration by mass a. 5.0 g of potassium dichromate in 100.0 mL of water

b. 3.0 g of sodium chloride in 50.0 mL of water

c. 0.25 g of cesium bromide in 25.0 mL of water

d. 0.75 g of methanol in 10.0 mL of water

e. 15.3 g of ethanoic(acetic) acid in 2.65 liters of water

4. What mass of solute is contained in each of the following solutions? a. 100.0 mL of 1.5% solution of calcium nitrate

b. 50.0 mL of a 2.5% solution of ammonium sulfate

c. 25.0 mL of a 0.50% solution of sulfuric acid

d. 75.0 mL of a 1.2% solution of hydrochloric acid

5. Calculate the mass of solute needed to prepare the following concentrations of solutions? a. 3.00 liters of 35% of HCl (aq)

b. 50.0 mL of 99.5% of CH3CO2H (aq)

c. 1.50 L of 95% of H2SO4 (aq)

d. 1.2 L of 3.26% of barium iodate

MOLAR SOLUBILITIES: Let’s take some notes….and learn how to make rock candy and slurpees in seconds.

6. A solution contains 26.5 g of NaCl in 75.0 g of H2O at 20 C. Determine whether the solution is

Procedure 1 : How to make a solution from stock solid

1. Calculate mass of solid solute required to make the solution : a. n = CV b. mass = n M

2. Acquire mass of solute

0.00 g

Tare button On / off

button

Weighing paper

4. Transfer dissolved solution into

volumetric flask ( using decanting

method )

3. Dissolve mass acquired into ½ final volume of distilled water ( using glass stirring rod )

5. Rinse the beaker with distilled water and

transfer solution into volumetric flask

6. Add water to volumetric flask and make up

solution to gradated mark by using meniscus

finder and eye dropper.

7. Stopper and Mix to achieve

homogeneous state

Sample Lab :

Problem : to make a 100.00 mL of a 0.125 mol/L solution of CuSO4  5H2O(s)

Experimental design :

A mass of CuSO4  5H2O(s) is weighed out and dissolved in water. The solution is then

transferred into a volumetric flask and ditilled water is added to make up to final volume

required.

Procedure :

1. Calculate the mass of CuSO4 5H2O(s) required to make solution

2. Acquire mass calculated with an electric balance

3. Dissolve mass acquired in ½ final volume of distilled water 4. Transfer solution into a clean 100 mL volumetric flask

5. Rinse glass utensils used and transfer rinse water into volumetric flask

6. Add water up to gradated mark of volumetric flask with eye dropper and meniscus finder 7. Stopper volumetric flask and Mix to achieve homogeneous solution.

Evidence :

Mass of CuSO4  5H2O(s) = 3.12 g

Color of solution = clear blue solution

Analysis :

Pre-lab calculation :

g 3.12 249.72 x mol 0.0125 nM mass mol 0.0125 L 0.10000 x 0.125 CV mol mol g L mol      

1 Cu = 63.55

1S = 32.07

Solutions - Practice - Making a Primary Solution

7. Calculate the mass of solid lye (sodium hydroxide) needed to make 500 mL of a 10.0 mol/L strong cleaning solution.

8. A technician prepares 500.0 mL of a 0.0750 mol/L solution of hydrogen peroxide as part of a quality-control analysis in the manufacture of hydrogen peroxide. Calculate the mass of hydrogen peroxide needed to prepare the solution.

9. Describe how to prepare 250.0 mL of a 0.200 mol/L solution of potassium chloride.

10. Describe how to prepare 500.0 mL of 0.150 mol/L solution of copper (II) sulfate-5-water.

Chemistry 20 Laboratory Process : Dilution

Problem : to learn how to make a solution from a concentrated solution

1. Calculate the volume of concentrated solution needed to make the diluted solution : C1V1 = C2V2

2. Acquire the solution from

stock bottle

4. Add water to volumetric flask and make up

solution to gradated mark by using meniscus

finder and eye dropper.

5. Stopper and Mix to achieve

homogeneous state

Sample dilution lab

Problem : to make 100.0 mL of a 0.100 mol/L solution from 1.00 mol/L stock solution

Procedure :

1. Wash all glassware with tap and distilled water ( all WET )

2. Pre-lab calculation : to calculate the volume of concentrated solution required for dilution

3. Acquire a volume of concentrated solution in a small beaker

- to prevent dilution in the WET beaker, wash the beaker out with a small aliquot of concentrated solution

4. Transfer concentrated solution into volumetric flask using pipet

- to prevent dilution in the WET pipet, wash the pipet out with a small aliquot of concentrated solution

- the pipet is calibrated to leave a small droplet of solution on the tip, do not dispense that small droplet into volumetric flask

5. Add distilled water into volumetric flask using meniscus finder and eye dropper

6. Stopper and mix to achieve homogeneous solution.

Evidence : ( none )

Analysis :

Pre-lab calculation :

_1.00 0.0100Lor 10.0mL

L 0.1000 x 0.100 V L mol L mol

Solutions - Practice Dilution

12. You have these stock solutions available: 2.0 mol/L NaCl, 4.0 mol/L KNO3, and 0.50 mol/L MgSO4.

Calculate the volumes you must dilute to make the following solutions: a. 500 mL of a 0.50 mol/L NaCl solution

b. 2.0 L of a 0.20 mol/L MgSO4 solution

c. 50 mL of a 0.20 mol/L KNO3 solution

13. You are asked to make a 1.50 L of a 0.250 mol/L HNO3 solution by diluting concentrated 16.0 mol/L

HNO3. What volume of the concentrated acid will be required to make the dilution?

14. Describe how to prepare 250.0 mL of 0.0500 mol/L solution of hydrochloric acid from a stock solution of 0.500 mol/L hydrochloric acid.

16. Radiator antifreeze (ethylene glycol) is diluted with an appropriate quantity of water to prevent freezing of the mixture in the radiator. A 4.00 liter container of 94% (v/v) antifreeze is diluted to 9.00 liters. Calculate the concentration of the final solution.

17. Many solutions are prepared in the laboratory from purchased concentrated solutions. Calculate the volume of concentrated 17.8 mol/L stock solution of sulfuric acid a laboratory technician would need to make 2.00 liters of 0.200 mol/L solution by dilution of the original concentrated solution.

18. In a study of reaction rates, you need to dilute the copper (II) sulfate in solution. You take 5.00 mL of 0.005000 mol/L of copper (II) sulfate and dilute it to a final volume of 100.0 mL.

a. Determine the final concentration of the dilute solution.

b. What mass of CuSO4 (s) is present in 10.0 mL of the final dilute solution?

Qualitative analysis of solutions.

Flame tests and solutions colors can be found on pages 6 and 11 in your data booklets. These tests allow us to figure out which ions are or are not in certain solutions.

Examples:

We can also use selective precipitation to create insoluble salts that can also be used to determine which ions were in solution and in what

concentrations.

1. Devise a procedure that will enable you to separate each ion from the other in mixtures of the following pairs of ions:

(a) Cl-(aq) and PO43-(aq)

(b) SO42-(aq) and I-(aq)

(c) OH-(aq) and I-(aq)

(d) Pb2+(aq) and Ca2+(aq)

CHEMICAL DETECTIVES

Mystery #1: A colourless solution produces a bright red flame when a wooden splint soaked in the solution is held in a Bunsen burner flame. What ion is present in the solution ? How else can we prove this?

Mystery # 2: A unknown solution is known to contain sodium hydroxide, sodium carbonate, or sodium chloride. When a solution of zinc sulfate is added, no reaction occurs. What is the unknown ?

Mystery #3: An unknown is a solution of barium nitrate, barium chloride, or sodium sulfide. When a solution of silver nitrate is added, no reaction occurs. What is the identity of the unknown ?

Mystery #4: A solution contains a mixture of ions. The solution is pink and produces a precipitate when sulfide ions in solution are added to it. What is the identity of one of the ions ?

Mystery # 5: A devious industrial worker, Harry Hazard, has flushed a chemical down the toilet. The chemical sleuths find traces of a green solution coming into the water treatment plant. After capturing a sample, they eagerly test it using qualitative analysis techniques learned in chemistry 20. The flame test produces no results. However iodide ions in solution produce a precipitate! What ion had Harry flushed down the toilet ?

Mystery # 6: Our sleuths suspect a solution of containing barium ions. How could they test the solution to determine this and eliminate all other suspect ions ?

Mystery # 7: A solution is suspected of containing lead (II) ions, a dangerous poison. An elderly widow is unsuspectingly ingesting the solution in her tea. (made by her doting grandson, Nea Farious) What tests could detect the lead ions in the tea ?