Chemistry Question?

Question

I have a question that I do not how to solve it even with the answer from the solution manual. Can someone please explain to me on how to solve it. Thank You. (Happy New Year!)

Q: An iron ore sample is dissolved in acid and the iron is obtained as Fe2+, which is analyzed by a titration with KMnO4. The titration reaction is:

5Fe^2+ + MnO4^- + 8H^+ ---> 5Fe^3+ + Mn^2+ + 4H2O

It is found that 24.00 ml of 0.0200 M KMnO4 solution is required to react with all the iron in a sample of ore weighing 0.4. What is the percent of iron in the ore?

A: 33.5%

Answer 1

The answer is quite straightforward. First, 24 ml (0.024 liters) of 0.02 M (moles/liter) KMnO4 is needed to react with the dissolved iron. First, you need to calculate how many moles of KMnO4 that is:

(0.024 liters)*(0.02 moles/L) = 0.00048 moles KMnO4 (or 0.48 millimoles)

Looking at the balanced titration reaction, one mole of KMnO4 (the equation omits the K because it isn't a crucial part of the reaction) reacts with 5 moles of Fe^2+, so you know:

(0.00048 moles MnO4)*(5 moles Fe^2+ / mole MnO4) = 0.0024 moles Fe^2+.

0.0024 moles of Fe^2+ are present in the ore. Next, we need to find out how much 0.0024 moles of Fe^2+ weighs in grams. The ore was dissolved in acid, which converted the atomic Fe in the ore into Fe^2+. However, the loss of two electrons upon reaction with the acid has a minimal effect on the mass of the Fe^2+ since the weight of those two electrons is very small relative to atomic masses. So you can use the atomic weight of atomic iron, which is 55.8 grams/mole. Then the next step is:

(0.0024 moles Fe^2+)*(55.8 grams Fe/mole) = 0.13392 g Fe.

You know that you have 0.4 (I'm assuming grams, though it's missing from your post) of ore, so the final step is:

0.13392 grams Fe / 0.4 g ore = 33.48%, which rounds to 33.5% using 3 significant figures.

I hope this helps!

Happy New Year to you as well!

Answer 2

Atomic weight: Fe = 55.845

24.00mLsoln x 0.0200molMnO4-/1000mLsoln x 5molFe2+/1molMnO4- x 55.845gFe/1molFe = (24.00)(0.0200)(5)(55.845) = 134gFe

134g/400g x 100% = 33.5%

I can only suppose that the "0.4" you give is kg of ore.

In the work above, the 24mL is given. The first factor comes from the titration data. The mL solution cancel, leaving moles MnO4-. The second factor comes from the balanced equation. The moles MnO4- cancel, leaving moles Fe2+. The third factor comes from the atomic weight. Moles Fe2+ cancel, leaving gFe.

Answer 3

OK. Interesting problem. Let's see how to figure it out.

You know the molar ration of Fe+2 to MnO4- is five to one.

So if you have a 0.02 M solution of KMnO4 you would need five times as many ml of the Fe+2 or 120 ml of a 0.02 M. So that means that you have 0.12 L * 0.02 moles/L = 0.0024 moles in your sample of Fe+2.

Now you need to convert that to grams, so you multiply the moles by the molar mass (atomic mass) of Iron, 0.0024 moles * 55.847 g/mole = 0.134 grams.

Then divide the 0.134 g of Fe by the grams of the sample, 0.4 g, 0.134/0.4 = 0.335, the decimal part of the whole. Multiply that by 100 to get the percent, 0.335 * 100 = 33.5%.

Answer 4

once you think of relating to the features modern-day in a real "soul mate" relationship, what one be conscious comes up maximum frequently on the precise of your checklist? Is it Chemistry? probable. it relatively is generally defined as a feeling that leaves you breathless, excited and susceptible interior the knees. hands sweat, the heart races and the physique tingles with frightened anticipation. the tip maximum might-be fans come to is that in the event that they journey those extreme thoughts in direction of somebody, they have the muse for an suitable and lasting relationship. suitable? in step with threat no longer. For this definition of chemistry is constrained to a minimum of one's actual reaction to a distinctive person. It lacks an entire length it is residing in our values, ideals, personalities and worldview. with a view to renowned you have the suitable connection with a ability (or latest) significant other, it is important to have a common wisdom of what genuine chemistry consists of, that encompass it. it is confusing to do. This extreme, actual hobby is the stuff that Oscar prevailing video clips and perfect-merchandising books are made up of. So, take a step back for a minute and spot in case you comprehend your self. :-)