If 34.2 grams of lithium react with excess water, how many liters of hydrogen gas can be produced at 299 Kelvin and 1.21 atmospheres? Show all of the work used to solve this problem.

Question

anonymous · Answer

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anonymous · Answer

someone? pleaz?
I'm about to take a quiz and I don't understand.

anonymous · Answer

@dumbsearch2 @DullJackel09 @Daniellelovee @DarkMoonZ

anonymous · Answer

@emo__gamer101 @elyrose101 @fluteprincess352 @Godlovesme @gelow @ghuczek @gahm8684 @hhelpplzzzz @HelpBlahBlahBlah @Hotchellerae21 @Here_to_Help15

godlovesme · Answer

sorry idk :(

anonymous · Answer

thx for looking at it :)

godlovesme · Answer

np :) wish i could help though..

jfraser · Answer

balanced reaction first

gelow · Answer

sorry don't now super sorry their is a medal thoe

anonymous · Answer

balanced reaction...like when you have those two group of numbers on either side of the equal sign and you balance them?

jfraser · Answer

it shouldn't be an equals sign, but you're basically on the right idea. You need to turn that word problem into a chemical equation with the proper formulas, and then balance

anonymous · Answer

how do I do that?

jfraser · Answer

if you're doing this kind of problem and you don't know how to balance a reaction, you've got a lot of work to do

jfraser · Answer

"lithium reacts with water" turn those words into proper chemical symbols

anonymous · Answer

Li + H2O?

jfraser · Answer

good, those are the reactants

jfraser · Answer

the products are actually not all given to you. hydrogen gas will be formed, which is $H_2$, but the other product is missing. This is a double displacement reaction

jfraser · Answer

do you know what the other product is going to be?

anonymous · Answer

the other product would by Lithium and Oxygen right? Lithium oxide?

jfraser · Answer

almost, it's really lithium hydroxide, $LiOH$

jfraser · Answer

not put all 4 of those together into a reaction

anonymous · Answer

Li + H2O --- H2 + LiOH

jfraser · Answer

good, now balance

anonymous · Answer

Li2 + 2 H2O = 2 LiOH + H2

anonymous · Answer

oops, i didn't mean to use =

anonymous · Answer

now I have to find out how many moles I have right?

jfraser · Answer

right

anonymous · Answer

so I got 2.48 moles of Lithium, for the H2O do I have 2.48 moles or do I have to times that by 2 because of the 2 before it?

jfraser · Answer

you don't need to know about the water, it's asking about the hydrogen $produced$ from the lithium

anonymous · Answer

oh ok

jfraser · Answer

2.48 moles of lithium is not correct. How did you get it?

jfraser · Answer

$$34.2\cancel{g \space Li} * (\frac{1 mol \space Li}{6.97\cancel{g \space Li}})$$

jfraser · Answer

then I bet you multiplied by 2 because of the coefficient in the reaction?

anonymous · Answer

the atomic mass is 6.9 when rounded. Since there's a 2 next to Li I timesed it by 2 and got 13.8. It said there was 34.2 grams of lithium so I divided 34.2 by 13.8. I ended up with2.48

jfraser · Answer

yeah, don't do that

anonymous · Answer

ok

jfraser · Answer

the coefficients are handled later, molar mass is always grams per $one$ mole, regardless of the coefficient in front of that particular reaction

anonymous · Answer

oh ok

jfraser · Answer

the proper conversion is the one I posted above

anonymous · Answer

so it would just be 6.97?

jfraser · Answer

no, it's $$34.2\cancel{g \space Li} * (\frac{1 mol \space Li}{6.97\cancel{g \space Li}})$$

anonymous · Answer

4.9

jfraser · Answer

yes, moles of Li

jfraser · Answer

$NOW$ the coefficients matter

jfraser · Answer

your balanced reaction should be$$2Li + 2H_2O \rightarrow H_2 + 2LiOH$$

anonymous · Answer

ok

jfraser · Answer

the mole ratio is now (properly) 2:1, so that becomes the new conversion$$4.96\cancel{moles \space Li} * (\frac{1mole \space H_2}{2\cancel{moles \space Li}})$$

anonymous · Answer

so 9.92?

jfraser · Answer

you multiplied

jfraser · Answer

you need to divide

anonymous · Answer

divide 1 by 2?

jfraser · Answer

divide the 4.96 by 2

anonymous · Answer

oh, I'm sorry that looked like it was multiplying

anonymous · Answer

2.48

jfraser · Answer

2.48 moles of $H_2$

anonymous · Answer

Ok, so now I know how many moles I have of Lithium and H2, now what do I do with them?

jfraser · Answer

the moles of lithium are gone, used up

jfraser · Answer

that's why the reaction arrow isn't an equals sign

jfraser · Answer

what you have now is moles of $H_2$

jfraser · Answer

but the problem is asking for $LITERS$ of $H_2$, which is a volume of gas.

You need to use the ideal gas law

anonymous · Answer

ohh, ok...pV=nRT?

jfraser · Answer

yes. You're given a pressure, a temperature, and now you've just solved for the moles. R is a constant, so just find the volume

jfraser · Answer

rearrange the equation first, and that will tell you which terms should be multiplied and which should be divided

anonymous · Answer

ok

anonymous · Answer

$$V = nRT \div P$$

jfraser · Answer

true. now just plug in everything you have

anonymous · Answer

ok, I got 50.31 as my answer

jfraser · Answer

that's what I get, GJ

anonymous · Answer

Thank you so much, now I think I know how to do that, and sorry for taking so long, I'm usually really smart but chemistry is my worst subject