Question

( 2 points) How much potassium chloride is produced, in grams, from a reaction that started with of 3.00 g of KClO3? (Assume all the KClO3 decomposes, and make sure the equation is balanced!!!)

KClO3 → KCl + O2

Answer 1

thanks for helping again!

Answer 2

First balance the equation.
Then convert the mass given to moles.
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To interconvert between mass and moles, use the relationship:

\(n=\dfrac{m}{M}\)

where, M=molar mass, m=mass, and n= moles.

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Next, use the stoichiometric coefficients to find moles produced.
Set up a ratio using the species of interest, like so:

e.g. for a general reaction:

\(\color{red}{a}A + \color{blue}{b}B\) \(\rightleftharpoons\) \( \color{green}{c}C\)

where upper case are the species (A,B,C), and lower case (a,b,c) are the coefficients ,

\(\dfrac{n_A}{\color{red}{a}}=\dfrac{n_B}{\color{blue}{b}}=\dfrac{n_C}{\color{green}{c}}\)

From here you can isolate what you need.
For example: if you have 2 moles of B, how many moles of C can you produce?

solve algebraically: \(\dfrac{2}{\color{blue}{b}}=\dfrac{n_C}{\color{green}{c}}\rightarrow n_C=\dfrac{2*\color{green}{c}}{\color{blue}{b}}\)

Answer 3

uh give me a min trying to understand haha

Answer 4

sure. all these stoichiometry problems are the same, so once you understand this one you can do all of them.

Answer 5

i know the equation but my professor sucks at explaining everything and he uses other university power point and he gets lost and all that stuff so i am just trying to learn

Answer 6

ok cool. we'll if you have doubts after you've tried it just gimme a shout

Answer 7

2 2 3 for the balancing

Answer 8

0.024 moles of KCLO3

Answer 9

now what do i do?

Answer 10

now you use a ratio to relate them.

\(\dfrac{0.024}{2}=\dfrac{n_{KCl}}{2}\)

you would solve algebraically, but since they coefficients are the same, then theres no work to be done (the coefficients cancel out).

so now that you have the moles of KCl convert to grams

Answer 11

so just divide 0.024/2 ?

Answer 12

then multiply bby 2?

Answer 13

that would be to find the moles of KCl, yes. But since you're multiplying and dividing by the same number, its redundant.

Answer 14

ops i am wrong i would end up with the moles

Answer 15

can you please explain ? sorry

Answer 16

sure, the process in these stoichiometry problems is to convert whatever you're given to moles, then use the coefficients (via the ratio) to find the moles of what you're looking for. THEN you convert the moles to whatever they're asking for (grams, volume, etc.)

So you have \(\dfrac{0.024}{2}=\dfrac{n{KCl}}{2}\rightarrow n_{KCl}=\dfrac{2*0.024}{2}=0.024 ~moles~of ~KCl\)

now you convert these to what they asked for.

Answer 17

thats the moles for KCLO3 though wait can i just divide the O3 moles from KCL? and get the answer?

Answer 18

its asking for potassium chloride

Answer 19

the moles is wrong its 0.0176

Answer 20

wait thats wrong too

Answer 21

the right moles is 0.012

Answer 22

can i just divide the O3 moles from KCL? and get the answer?

no, you can't do that.

Is 0.012 moles for KClO3?

Answer 23

yes

Answer 24

okay, so from the balanced equation we know that the coefficients are the same. So the moles of KClO3 are equal to the moles of KCl.

(This is apparent when you look at the ratio above)

So now that you know the moles of KCl, convert them to mass

Answer 25

uhhh yes i guess because its 2 2 3

Answer 26

i am so lost sorry!! i know this the moles part

Answer 27

it's because it's 2:2.

IN comparison, if you were asked to find the moles of \(O_2\) produced, then it'd be

\(\dfrac{0.012}{2}=\dfrac{n_{O_2}}{3}\)

Answer 28

right

Answer 29

so i checked and 0.024 moles was the right amount of mole of KClO3

Answer 30

can't be because after you balance and multiply 2*39+2*35.45*16*6

Answer 31

then divide 3 by that

Answer 32

35.45+16*6

Answer 33

you dont include the coefficient into the formula

it;s just \(KClO_3\), not \(2~times~KClO_3\)

Answer 34

oh yeah i was right the first time then

Answer 35

so (0.024/2)= (1/2)

Answer 36

because moles of KCL is just 1 on the other side

Answer 37

hm no you dont need to divide by 2.

It;s just algebra,

\(\dfrac{0.024}{2}=\dfrac{x}{2}\)

solve for x

\(x=0.024\)

Answer 38

you actually dont know the moles of KCl, so it's not 1. it's an unknown

Answer 39

so thats it?

Answer 40

0.024 is the moles of KCL?

Answer 41

and convert to grams now?

Answer 42

thats the moles, yeah. (this is useful when the coefficients arent the same)

now convert to mass

Answer 43

yep

Answer 44

so 0.024*122.45

Answer 45

i mean 0.024 * 74.45

Answer 46

yeah, the bottom one is right

Answer 47

so 1.79 g THANK YOU SO MUCH! I CONFUSED MYSEL

Answer 48

can you help me with one more problem? this is the last one

Answer 49

yeah, its confusing at first. you'll be fine after you do a few of them.

and yeah, post it

Answer 50

okay about to i will post a screenshot of this because it has graph