Question

The mineral pyromorphite has the formula \(\text{Pb}_5(\text{PO}_4)_3\text{Cl}\). What mass percent of chlorine does it contain?

i use \[\text{mass %} = \frac{\text{mass of Cl}}{\text{mass of} \;\text{Pb}_5(\text{PO}_4)_3\text{Cl}}\times 100\text %\]
right?

Answer 1

i got \[\frac{35.45}{1,356.36} \times 100\text % \implies 0.0261 \times 100 \text %\implies 2.61 \text%\]
is that right?

Answer 2

Pb5(PO4)3Cl

Pick a random mass of Pb5(PO4)3Cl to work with I'm going to pick 100g

\[(\frac{( 100g_{Pb_5(PO_4)_3Cl} *\frac{35.45g/mol_{Cl}}{1356g/mol_{Pb_5(PO_4)_3Cl}} )}{100g})* 100 =2.6 \]

Your method looks good I just did it the longer way molecular mass ratio is constant so I didnt really need to apply gravimeter factor :)

Answer 3

sorry that should be 2.61% :)

Answer 4

the answer says it shoulld be 10.50% @Australopithecus that's why i was asking

Answer 5

I think your source is wrong

Answer 6

i doubt that

Answer 7

hmm well our answer makes sense logically as well chlorine takes up only a small fraction of the mass that all the other elements take up, I mean it has 5 atoms of lead in it

Answer 8

and only 1 of chlorine, what makes you doubt our answer?

Answer 9

what makes me doubt is im not good in chemistry

Answer 10

Well I'm a laboratory technologist and currently obtaining a degree in biochemistry, trust me it is the correct answer

Answer 11

The general equation should be,

\[(\frac{Molecular Mass_{Cl}}{Molecular Mass_{Pb_5(PO_4)_3Cl}})*100 = Mass_{Cl}%\]

Answer 12

well i'll still want to see how 10.5 was in the choices

Answer 13

That should be mass percent Cl

Answer 14

people dont post choices unless they make sense

Answer 15

Must have been a miss calculation of the molecular mass of pyromorphite

Answer 16

I used wolframalpha to check its molecular mass btw

Answer 17

then how to get that miscalculation?

Answer 18

https://www.wolframalpha.com/input/?i=+Pb5%28PO4%293Cl

Answer 19

who knows, but we both came to the same conclusion and furthermore our solution makes sense 10% doesn't make any sense look at the compound the majority of mass will be taken up by lead

Answer 20

i think oxygen takes the bigger percent...

Answer 21

no, do you understand what molecular mass is?

Answer 22

it is the ratio of mass per mole

Oxygens molecular mass is approximately

(15.9994g/mol )*4 = (63.9976g/mol)*3 = 191.9928g/mol

Lets look at leads molecular weight in this compound

207.2g/mol = Molecular mass of Lead

207.2g/mol*5 = 1036g/mol of lead In the compound

Answer 23

it seems from this website it really is 2.61 http://webmineral.com/data/Pyromorphite.shtml

Answer 24

i think i do understand the concept of molecular mass btw....i did answer this...lol

Answer 25

chlorine has 35.45grams per 1mol of compound
lead has 1035g per 1 mol of compound

Answer 26

Well you should have known you were right logically, and furthermore you stated that oxygen takes up more mass than lead in the compound :S

Answer 27

lol no need to explain. i already showed that i got 2.61...what i was asking how 10.5 was got

Answer 28

That is a mystery that is not worth solving :)

Answer 29

i was referring to the mole ratio that oxygen takes more

Answer 30

lead has 1035g per 1 mol of compound
Oxygen has 191.9928g per 1 mol of compound

Answer 31

it is an incorrect assumption on your part I just wanted to point out

Answer 32

I'm not trying to be a jerk btw :)

Answer 33

you always have to remember molecular mass is expressed per 1 mol

Cl has a molecular mass of
\[\frac{35.45g}{1mol}\]

Answer 34

i was lol

Answer 35

I'm sorry you stated you are not good at chemistry I just wanted to make sure you knew please don't take offense