PRELAB QUESTIONS ___

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5

PRELABQUESTIONS ___

  1. Identify the five possible anions which are to be identified in this experiment.

ChlorideCl,Bromide Br,Iodide I,Carbonate CO32-,Sulfate SO42-

  1. How many of these five anions will appear in your unknown sample?

Two,Bromide and Iodide

  1. Four of the chemicals used to make the known and unknown samples contain the sodium ion. How will this affect your results in this experiment?

Sincesodium is more reactive, it displaces less reactive elements andhence helps in the formation of insoluble salts.

4.What purpose does the centrifuge have in this experiment?

Soas to separate particles with different densities, the precipitatedparticles will settle at the bottom of the test tube.

5.Four of positive tests for an unknown ion include the formation of aprecipitate. Which ion has a positive test that involves theformation of gas?

Carbonateion CO32-

POSTLABQUESTION ___

  1. Write the name of the following ions.

  1. ClChloride ions

  2. BrBromide ions

  3. IIodide ions

  4. SO42-Sulphate ions

  5. N03Nitrate ions

  6. C2H3O2Methanoate ions

  7. CO32-Carbonate ions

  8. NH4+Ammonium ions

  9. Ba2+Barium ions

  10. Cu2+Copper (II) ions

  11. Fe3+Iron (III) ions

2.Write the formula of the following ions.

a.hypochlorite – ClO

b.chlorate – ClO3

c.magnesium – Mg2+

d.sulfite – SO32-

e.bicarbonate – HCO3

f.aluminum – Al3+

g.sulfide – S2-

h.fluoride – F

i.nitride – N3-

j.phosphate – PO43-

k.cobaltic or cobalt(III) – Co3+

3.Write the formulas of the following compounds.

a.magnesium acetate – Mg(CH3COO)2

b.sodium sulfate – Na2SO4

c.iron(III) sulfite – Fe2(SO3)3

d.potassium bicarbonate – KHCO3

e.zinc oxide – ZnO

f.copper(II) oxide – CuO

g.sulfur dioxide – SO2

h.dinitrogen monoxide – N2O

i.aluminum phosphate – AlPO4

j.magnesium nitride – Mg3N2

k.sodium oxalate – Na2C2O4

4.Write the name of the following formulas.

a.Mg3P2MagnesiumPhosphide

b.Ca(HCO3)2CalciumBicarbonate

c.CaF2CalciumFluoride

d.Al2(CO3)3Aluminiumcarbonate

e.K3PO3PotassiumPhosphite

f.FeCl3Iron(III) Chloride

g.Ni2S3Nickel(III) Sulfide

h.CaC2O4CalciumOxalate

i.Zn(C2H3O2)2ZincAcetate

j.CrO3ChromiumTrioxide

k.MnO2ManganeseDioxide

5.A student analyzed an unknown sample that contained a single anion.The sample gave a yellow precipitate upon addition of a solution ofAgNO3 which did not dissolve in ammonia. Which anion is present inthe unknown solution? Write the corresponding net ionic equation.

Ipresent

Ag+(aq)+ I(aq) AgI(s)(yellow precipitate)

6.A student analyzed an unknown sample that contained a single anion.The sample gave a white precipitate upon addition of a solution ofAgNO3which dissolved in ammonia. Which anion is present in the unknownsolution? Write the corresponding net ionic equation.

Clpresent.

Ag+(aq)+ Cl(aq) AgCl(s)

7.Iodine (I2) and bromine (Br2) are soluble in mineral oil and slightlysoluble in water. Why? Suggest another solvent, hexane or alcohol,which can be used instead of mineral oil? Explain.

CH3CH2CH2CH2CH2CH3 CH3CH2OH

Hexane Alcohol

Theyare made up of molecules that are nonpolar.

Hexanecan be used as a solvent because it is nonpolar. Alcohol is polar,and iodine and bromine dissolves in nonpolar solvents.

8.Write the net ionic equations for the following reactions.

a.An aqueous solution of sodium carbonate is added to an aqueoussolution of calcium chloride.

Calciumcarbonate is precipitated.

CO32-(aq)+ Ca2+(aq) CaCO3(s)

b.An aqueous solution of sodium phosphate is added to an aqueoussolution of strontium chloride. Strontium phosphate is precipitated.

2PO3-4(aq)+3 Sr2+(aq) &nbspSr3(PO4)2(s)

c.An aqueous solution of potassium sulfate is added to an aqueoussolution of barium chloride.

Bariumsulfate is precipitated.

SO42-(aq)+ Ba2+(aq)BaSO4(s)

d.An aqueous solution of ammonium iodide is added to an aqueoussolution of silver nitrate. Silver Iodide is precipitated.

I(aq)+Ag+(aq)AgI(s)

References

Thomson,R.B. (2012). IllustratedGuide To Home Chemistry Experiments.Gravestein: O’Reilly Media Inc.