Question

how many millimeters of manganese metal, with a density of 7.43 g/ml would be needed to produce 21.7 grams of hydrogen gas in the single replacement Mn+H2O -> MnO + H2

Answer 1

Are you sure millimeters is the correct unit?

Answer 2

yes and i know tht the eqaution is already balamced i really need someone to explain it so i know how to do them

Answer 3

Well if millimeters is the correct unit, they you can't work it out. Millimeter is a measurement of length, not of mass or amount of substance. If the question is referring to a strip of manganese metal, then we need to know the diameter of that strip.

Answer 4

oh im so sorry its millileters

Answer 5

Ok. Then the first step would be to convert 21.7 grams of hydrogen gas in to moles. Do you know how to do that?

Answer 6

i am pretty sure but not 100%

Answer 7

Ok, try calculate the amount of hydrogen gas in moles and if there's a mistake I'll correct you.

Answer 8

okay thank you

Answer 9

what wud the abbrevaitaion be for hydrogen gas?

Answer 10

What do you mean by abbreviation?

Answer 11

like what letters?? mean hydrogen gas??

Answer 12

Do you mean: \[H_2\]

Answer 13

oh okay yes

Answer 14

just where do i find the mass on the periodic table?

Answer 15

The atomic mass of hydrogen should be under the letter "H". You should find it on the top left of most periodic tables.

Answer 16

okay i got the answer of 21.5299molH2

Answer 17

That's not correct... can you show me how you got 21.5299 mol?

Answer 18

21.7 grams H2 X 1mol h2 21.7/1.0079=21.5299
-------------
1.0079 g H2

Answer 19

The problem here is that its H2, not H. The mass on the periodic table is the atomic mass for one hydrogen atom. In hydrogen gas molecules, there are two hydrogen atoms. So you need to multiply the mass on the periodic table by two.

Answer 20

ohh okay got it so the correct answer will be.... im doing it now

Answer 21

Take your time

Answer 22

I got 10.76496

Answer 23

Great. Now we need to look back at the balanced equation:
\[Mn+H_2O \rightarrow MnO+H_2\]
Do you know how to deduce the molar ratios from a chemical equation?

Answer 24

no sorry :(

Answer 25

what does it mean to deduce the molar ratios??

Answer 26

Don't worry :) When you look at different chemical equations, you sometimes see numbers (co-efficients) before the molecules, like the following:

\[6CO_2+6H_2O \rightarrow C_6H_{12}O_6+6O_2\]
In the equation above, 6 moles of CO2 produces one mole of C6H12O6. These are molar ratios. In our own question, all coefficients are 1 but we dont write them out since, it is not necessary.

Answer 27

oh okay yea i know tht

Answer 28

Now, we need to look at the two things we concern about: hydrogen gas and manganese metal. We can ignore the others since the question doesnt concern other things in the reaction. We notice that the coefficient before H2 (hydrogen gas) and Mn (manganese metal) is 1 (not written, since it's 1).

Answer 29

So this means that one mole of H2 will produce 1 mole of Mn. Since we have 10.76496 moles of H2, we can deduce that 10.76496 of Mn is needed for that amount of H2 to be produced.

Answer 30

That gives us the amount of Mn involved in the reaction. Now, since the question does not use moles, we need to convert moles back to grams. Do you know how to do that?

Answer 31

okay

Answer 32

yes i do i think i got wud the final answer be 80.31mL??

Answer 33

I got 79.59 ml, but I'm sure its just the significant figures of the manganese mass used.

Answer 34

I think you've got it.

Answer 35

oh okay thank you soooo much! if i have any others im suck on or need u to check will you?

Answer 36

The key to solving these questions is to convert everything in grams into moles then use the molar ratios to convert moles of one thing to another, and finally convert that mole to grams again.

Answer 37

Sure. Just drop me a message if you have anything else to ask in the future.

Answer 38

okay i will thank you :)

Answer 39

:)