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### L35

Posted: **Fri Oct 06, 2017 1:37 am**

by **Maldonado3K**

Hi there, I was just wondering if someone could give me some basic steps or guidance to solve problem L35.

"Sodium bromide, NaBr, which is used to produce AgBr for use in photographic film, can itself be prepared as follows...

What mass of iron, in kilograms, is needed to produce 2.50t of NaBr?'

Thank you!

### Re: L35

Posted: **Fri Oct 06, 2017 9:36 am**

by **Kyra Dingle 1B**

Before doing anything it is important to check that all the equations are balanced!

1. Convert the 2.50 t to grams. This is best done by converting first to kilograms and then converting that value to grams.

2. Convert the g of NaBr to moles by dividing by the molar mass of NaBr.

3. Once you found the moles of NaBr, convert it to moles of Fe3Br8 by dividing the value by the number of moles of NaBr in the third equation and then multiplying it by the number of moles of Fe3Br8 in the third equation. The number of moles of each are found when the equation is balanced. (Hint: you should have 8 moles of NaBr and 1 mole of Fe3Br)

4. Convert to moles of FeBr2 by dividing by the number of moles of Fe3Br8 found in the second equation and multiplying by the number of moles of FeBr2 found in the second equation.

5. Convert to moles of Fe by dividing by the number of moles of FeBr2 found in the first equation and multiplying by the number of moles of Fe found in the first equation. (HInt: there should be one mole of each in the first equation.)

6. Convert the moles of Fe to grams of Fe by multiplying the value by the molar mass of Fe.

7. Convert grams of Fe to kilograms. You should now have your answer!

Hope this helps

### Re: L35

Posted: **Fri Oct 06, 2017 10:08 am**

by **Yingru_Huang_3E**

First, make sure the chemical equations are balanced, so that you can properly figure out the needed mass of iron.

First, convert the metric ton (t) to grams, by first converting the metric ton to kilograms (1000 kg= 1 metric ton), then grams (1000 grams = 1 kg). You should get about 102.9 g of NaBr

Then, you have to find the mass of Fe needed in the initial reaction. The key to solve this is to work from the final reaction backwards; find which parts of each chemical reaction contains iron. So, since 102.9 g of NaBr is a mole, use the moles via all coefficients that contain Fe, then the fact that 1 mol Fe=55.845 g Fe to find the mass.

I know this isn't the best explanation, but I hope this helps!