Question

A solution contains .530 mol of isopropanol (C3H7OH) dissolved in .870 mol water.
( a ) What is the mole fraction of isopropanol?
(b ) What is the mass percent of isopropanol?
(c ) What is the molality of isopropanol?

Answer 1

@Photon336

Answer 2

@ganeshie8

Answer 3

do u know the formula for mole fraction?

Answer 4

@priyar no

Answer 5

molefraction of solute = moles of solute/(moles of solute+moles of solvent)

Answer 6

here what is the solute and solvent?

Answer 7

The solute is isopropanol and the solvent is water.

Answer 8

good so plug in the appropriate values in the abv eq.

Answer 9

mol frac = .530/(.530+.870)

Answer 10

good!!

Answer 11

=.37857

Answer 12

good job!

Answer 13

Is that it for that part?

Answer 14

yup!

Answer 15

what is mass percent?

Answer 16

not really sure. I know I will need to times by 100

Answer 17

i thought u must have learnt it in ur school..

Answer 18

anyway, mass percent = (mass of solute/mass of solution) * 100

Answer 19

@priyar Would the solution be water and the isopropanol?

Answer 20

yes together they make the solution

Answer 21

mass percent = .530/1.4 *100

Answer 22

=38%

Answer 23

no u have not substituted the mass..

Answer 24

u have substituted the moles..

Answer 25

So do I need to change the solute and solution to grams?

Answer 26

yes

Answer 27

31.85 g Iso/109.333g Iso &H2O *100=29.13

Answer 28

29.13%

Answer 29

@priyar would it be just 29%?

Answer 30

31.85 g Iso/109.333g Iso &H2O *100=29.13??

Answer 31

@priyar Is that wrong?

Answer 32

31.8g is correct but what is "Iso" ???

Answer 33

Oh, I was abbreviating isopropanol

Answer 34

Is the rest of it correct?

Answer 35

oh ok and for water it is .870 *18 =15.66 to get mass of solution add both masses

Answer 36

@Photon336 they've asked for "molality"

Answer 37

i see then that's mol of solute per kilogram of solution

Answer 38

@staldk3 what do u get as the mass of solution?

Answer 39

Wait what about the water?

Answer 40

mass of water =15.66g

Answer 41

now tell me the mass of the entire solution..

Answer 42

15.66g+31.8g = 47.46g

Answer 43

good! so what will be the mass percent?

Answer 44

67.00%

Answer 45

great!

Answer 46

now u must be knowing molality formula right?

Answer 47

@staldk3

Answer 48

m= moles solute/kg solvent

Answer 49

good! now plug in the appropriate values!

Answer 50

31.8g/.01566kg

Answer 51

great! simplify

Answer 52

I got a crazy number

Answer 53

2030.65

Answer 54

yes correct.

Answer 55

did u understand ?

Answer 56

@priyar Sorry. I had internet issues.

Answer 57

@priyar It counted it wrong when I put 2030 for sig figs

Answer 58

its ok! was the answer to the 3rd part wrong?

Answer 59

@staldk3 ?

Answer 60

Yes. Sorry. Went to do something since no one was on.

Answer 61

np. but what did u say abt significant fig.

Answer 62

Shouldn't it be only 3 sig figs? So 2030?

Answer 63

are they asking for sig fig in the Q?

Answer 64

They usually want sig figs. Is 3 sig figs not right?

Answer 65

2030.65 this has 6 sig fig

Answer 66

Right but when you're doing problems you're suppose to take the least amount of sig figs as what the problem/equation contains right?

Answer 67

hey sry.. i don't know how i failed to notice the mistake when u wrote 31.8/0.01566... no of moles os solute should be the numerator..not mass..

Answer 68

u wrote the formula correctly..but plugged in the wrong value....

Answer 69

number of moles of solute should be the numerator..not mass..

Answer 70

So I should flip it?

Answer 71

why?no

Answer 72

can u write the formula again?

Answer 73

m= moles solute/kg solvent

Answer 74

Sorry had to find it.

Answer 75

u must remember these formulae always..coz u use them a lot ... now plug in the correct values..

Answer 76

.530/.01566

Answer 77

=33.84

Answer 78

correct!

Answer 79

So would it be 33.8 for sig figs?

Answer 80

no..the least is 2 sig. fig

Answer 81

So 34

Answer 82

Perfect!

Answer 83

good job!

Answer 84

Thanks and thanks for the help!

Answer 85

U r welcome!