# Blog Archives

## What Is The Total Molar Concentration of Ions?

What is the total molar concentration of ions in each of the following solutions? Assuming complete dissociation.

1.)   .750 M of K2CO3

2.)   .355 M of AlCl3

## What Is The Mass Percent?

A sample weighing 14.98g and containing a small amount of copper was treated to give a solution containing aqueous Cu^2+ ions.  Sodium iodide was then added ti yield solid copper (I) iodide plus I3^- ion, and the I3^- was titrated with thiosulfate, S2O3^2-.  The titration required 10.49mL of .100M Na2S2O3 for complete reaction.  What is the mass percent copper in the sample?  The balanced equations are…

2Cu^2+(aq)+5I^-(aq)—->2CuI(s)+I3^-(aq)

I3^-(aq)+2S2O3^2-(aq)—->3I^-(aq)+S4O6^2-(aq)

## What Is The Mass Percent?

The metal content of iron in ores can be determined by a redox procedure in which the sample is first oxidized with Br2 to convert all the iron to Fe^3+ and then titrated with Sn^2+ to reduce the Fe^3+ to Fe^2+.  The balanced equation is:

2Fe^3+(aq)+Sn^2+(aq)—->2Fe^2+(aq)+Sn^4+(aq)

What is the mass percent of Fe in a .1875g sample of ore if 13.28mL of a .1015M Sn^2+ solution is needed to titrate the Fe^3+?

## What Is The Molar Concentration?

What is the molar concentration of As(III) in a solution if 22.35mL of .100M KBrO3 is needed for complete reaction with 50.00mL of the As(III) solution?  The balanced equation is…

3H3AsO3(aq)+BrO3^-(aq)—->Br^-(aq)+3H3AsO4(aq)

## What Is The Concentration?

Dichromate ion, Cr2O7^2-, reacts with aqueous iron(III) ion in acidic solution according to the balanced equation

Cr2O7^2-(aq)+Fe^2+(aq)+14H^+(aq)—->2Cr^3+(aq)+6Fe^3+(aq)+7H20(l)

What is the concentration of Fe^2+ if 46.99mL of .2004M K2Cr2O7 is needed to titrate
50.00mL of the Fe^2+ solution?

## Molar Concentration

What is the molar concentration of Br^- ions in a 0.225M (aq) solution of FeBr3, assuming complete dissociation?

## Molar Concentration

What is the molar concentration of As(III) in a solution if 25.35mL of 0.110MKBrO3 is needed to titrate 53.55mL of the As(III) solution? The balanced equation is
3H3AsO3(aq)+BrO−3(aq)→Br−(aq)+3H3AsO4(aq)

## Concentration

Iodine, I2, reacts with aqueous thiosulfate ion in neutral solution according to the balanced equation I2(aq)+2S2O2−3(aq)→S4O2−6(aq)+2I−(aq).

How many grams of I2 are present in a solution if 40.00mL of 0.150M Na2S2O3solution is needed to titrate the I2solution?

## Molar Concentrations

Titration with solutions of potassium bromate, KBrO3, can be used to determine the concentration of As(III).

What is the molar concentration of As(III) in a solution if 25.35mL of 0.110M KBrO3 is needed to titrate 53.55mL of theAs(III) solution? The balanced equation is
3H3AsO3(aq)+BrO−3(aq)→Br−(aq)+3H3AsO4(aq)