# Chem

posted by .

Potassium permanganate (KMnO4) solutions are used for the determination of iron in samples of unknown concentration. As a laboratory assistant, you are supposed to prepare 200. mL of a 0.300 M KMnO4 solution. What mass of KMnO4, in grams, do you need?

I got 60, but that's wrong. I know you have to get moles by using the molarity formula and then change it into grams using molar mass, but I can't get the right answer/ Any help is appreciated!

• Chem -

You appear to know what to do; the problem may be that you're just making a math error. Post your work and I'll find the error for you.

• Chem -

the molar mass of KMnO4 is

39.098 + 54.938 + 15.999*4 = 158.032

200 ml = 200 mL / 1000 mL/L = 0.2 L

0.2 L * 0.3 moles/L = 0.06 Moles KMnO4
= 0.06 * 158.032 g/mol = 9.48 g KMnO4

• Chem -

You must have changed your method because you're no longer reporting 60. You're right, 60 is millimoles KMnO4 you need which is 0.06 mols. Then g = mols x molar mass = 0.06 x 158.034 = 9.48 g KMnO4.
That looks good to me.

• Chem -

It says that the molarity is.3M so you would do .3 mol/1 L*.2L. .6mol*157g=94.2. That's my new answer.

• to annonymus--Chem -

nope. 0.3 x 0.2 is right but that answer is 0.06 and not 0.6 and that x 158.34 (not 157) = 9.48g.

## Similar Questions

1. ### Chemistry

In a previous experiment, 0.800 g of the green complex iron salt was placed in an Erlenmeyer flask and heated with concentrated sulfuric acid until all oxalate ion was destroyed (CO2, SO2 and H2O are formed). Ferric ion (Fe3+) remained …
2. ### Chemistry

A solution of hydrogen peroxide, H2O2 , is titrated with potassium permanganate, KMnO4 , according to the following equation: 5 H2O2 + 2 KMnO4+ 3H2SO4 -> 5O2 + 2 MnSO4 +8H2O + K2SO4 It requires 46.9mL of 0.145 mol/L KMnO4 to titrate …
3. ### Chemistry

solution of hydrogen peroxide, H2O2 , is titrated with potassium permanganate, KMnO4 , according to the following equation: 5 H2O2 + 2 KMnO4+ 3H2SO4 -> 5O2 + 2 MnSO4 +8H2O + K2SO4 It requires 46.9mL of 0.145 mol/L KMnO4 to titrate …
4. ### AP CHEM

Please help me with thses AP CHEM homework problems and show the steps to how to find the solutions: Solid Liquid Titrations: Determine the concentration of the indicated liquid unknown given the mass of a solid standard and the buret …
5. ### AP Chem

A solution of hydrogen peroxide, H2O2, is titrated with a solution of potassium permanganate, KMnO4. It requires 51.7 mL of 0.145 M KMnO4 to titrate 20.0 g of the solution of hydrogen peroxide. What is the mass percentage of H2O2 in …
6. ### Chemistry HELP!

In order to standardize a KMnO4 solution, 0.3498 g Na2C2O4 was dissolved in 30 mL water and 15 mL 3.0 M H2SO4. The KMnO4 solution was added to the Na2C2O4 solution until a pale pink color persisted. The titration took 29.5 mL of KMnO4 …
7. ### Chemistry HELP!

In order to standardize a KMnO4 solution, 0.3498 g Na2C2O4 was dissolved in 30 mL water and 15 mL 3.0 M H2SO4. The KMnO4 solution was added to the Na2C2O4 solution until a pale pink color persisted. The titration took 29.5 mL of KMnO4 …
8. ### chemistry

ou weigh out Potassium Permanganate, Mass of KMnO4 (MW=158.034).......... 0.1569 g You dissolve it completely in water.......... 46.00 mL (a) Molarity of MnO4- solution........................... ________________ M You pipet out your …
9. ### chemistry

ou weigh out Potassium Permanganate, Mass of KMnO4 (MW=158.034).......... 0.1569 g You dissolve it completely in water.......... 46.00 mL (a) Molarity of MnO4- solution........................... ________________ M You pipet out your …
10. ### Chemistry

Potassium permanganate (KMnO4) solutions are used for the determination of iron in samples of unknown concentration. As a laboratory assistant, you are supposed to prepare 700. mL of a 0.200 M KMnO4 solution. What mass of KMnO4, in …

More Similar Questions