Question

I need help with HW please!

Answer 1

@Vocaloid

Answer 2

are you familiar with the boiling point and freezing point elevation/depression formulas?

Answer 3

yes

Answer 4

good, let's start on the first problem then

Answer 5

okay

Answer 6

i think we willing be using the boiling point formula first

Answer 7

yes

Answer 8

then the freezing point

Answer 9

delta T = Kb * molality * i

Answer 10

the problem is the 104.75 do i subtract it from 100?

Answer 11

yes

Answer 12

that gives you your boiling point elevation (deltaT)

Answer 13

use that to solve for molality

Answer 14

then plug that into the freezing point formula

Answer 15

3.10=m

Answer 16

not quite

Answer 17

remember that i = 3 in this case

Answer 18

i did 0.51 x 3

Answer 19

then 1.53 divided by 4.75

Answer 20

where are you getting .51 from

Answer 21

kb= 0.51

Answer 22

kf= -1.86

Answer 23

oh right

Answer 24

correct

Answer 25

yes, that makes your molality 3.10

Answer 26

then plug that into the freezing formula

Answer 27

-17 is the freezing point?

Answer 28

good

Answer 29

i did -1.86 x 3.10 x 3

Answer 30

yes good

Answer 31

thx but can u help me with the others too?

Answer 32

do u want me to make new post?

Answer 33

sure

Answer 34

nah it's ok

Answer 35

thank you

Answer 36

i have no idea how to do the next one

Answer 37

for the next one you want to set up two equations, one for the pee and one for the pee + salt

Answer 38

so how would i set it up?

Answer 39

hm let me see

Answer 40

this one's a bit tricky

Answer 41

@sweetburger would you mind checking me on this one? I have an idea but i'm not 100% sure. it's the second problem on the page

Answer 42

Which question number 10?

Answer 43

yes

Answer 44

\[\Delta T = -5.27C^o - (-3.16C^o)=-2.11 \] to represent the change in temperature. Otherwise looks good.

Answer 45

i'm not certain if i should use 2 for van't Hoff since this isn't pure water

Answer 46

( i mean, not a solution made from pure water + solute)

Answer 47

Van hoffs is still 2. Assume the question is relatively simple.

Answer 48

gotcha

Answer 49

in that case, we just set it up like this

Answer 50

oh so we have to convert it?

Answer 51

yes

Answer 52

just convert 15 grams of NaCl to moles

Answer 53

so first we solve for the m then convert

Answer 54

convert NaCl first

Answer 55

m= 2.1

Answer 56

hold on a sec

Answer 57

@MarcoReus11 how did you get m= 2.1?

Answer 58

first we convert 15 g NaCl to moles, giving us .256 moles

.256/.175kg = 1.46 molality

Answer 59

0.51 x 2=1.02/2.11

Answer 60

2.11/1.02

Answer 61

Where does .51 come from?

Answer 62

we can't use 0.51 since this isn't water

Answer 63

thats what kb=

Answer 64

Follow what @Vocaloid did above.

Answer 65

we're solving for the Kb of pee

Answer 66

oh i see

Answer 67

0.72=kb

Answer 68

good

Answer 69

so its 0.72?

Answer 70

i would label it 0.72 KF right?

Answer 71

yes, Kf

Answer 72

(not Kb, that was a typo )

Answer 73

yea Kb is the base dissociation constant to measure the relative strength of a base.

Answer 74

okay just making sure thx

Answer 75

ready for 11?

Answer 76

yup

Answer 77

i think i should be ok on my own now

Answer 78

for 11, we solve for molarity

Answer 79

okay

Answer 80

it gives up 2 product with grams

Answer 81

so are we suppose to set up 2 different equation?

Answer 82

just one equation this time

Answer 83

okay

Answer 84

were you given a freezing point depression constant for ether?

Answer 85

yes -116.87

Answer 86

what about the constant?

Answer 87

Kf?

Answer 88

-1.86