Question

Five grams of sodium are combined with unlimited bromine. How many moles of bromine are used up? How many liters of bromine would be used if the reaction took place at STP?

Answer 1

I think it's 0.1088 mol Br2 and 2.44 L Br2.

Answer 2

You're pretty close, make sure you round/check your sigfigs for your number of moles and divide by the correct pressure for your volume.

Answer 3

@a1234 write out our reaction first between na and br. including reactions and product

Answer 4

I started out with 22.38 g NaBr. The balanced equation is 2Na + Br2 = NaBr.

Answer 5

okay great. so you know you have unlimited bromine

Answer 6

yes

Answer 7

STP = standard temperature and pressure. there's actually a rule behind this do you know what it is?

Answer 8

1 mole of gas at STP is 22.4 liters

Answer 9

exactly

Answer 10

So I converted 22.38 g NaBr to moles:

22.38 g NaBr (1 mole/102.89 g NaBr)
0.2175 mole NaBr

Answer 11

you start out with 5 grams of Na right? and you know Br is unlimited @a1234 that's a hint that you must always make sure to take note of that because you automatically know that Na will run out first make sense?

Answer 12

yes

Answer 13

The reason why this is important is because to find the number of moles of NaBr we've got to use the limiting reagent, what runs out first. we know we've got unlimited Br so that doesn't matter when calculating the moles. so we use number moles of sodium multiplying that by the molar ratio. check it out below.

\[5~grams~of~sodium*(\frac{ moles }{ molar~mass~sodium })*(\frac{ NaBr }{ 2Na })\]

Answer 14

@a1234

Answer 15

The molar mass of sodium is 22.99 g.
5(1 mole/22.99 g Na)
.2175 mole

.2175 mole Na(NaBr/2Na)

So it's .2175/2?

Answer 16

yes

Answer 17

do you get why sodium is the limiting reagent?

Answer 18

Yes, we have unlimited bromine

Answer 19

okay great

Answer 20

the concept though that every gas occupies 22.4L at STP is a powerful one. Just remember that this will only apply to the conditions at STP

Answer 21

yes

Answer 22

Hope this clarifies things

Answer 23

that's correct because you're told this is happening at STP