Question

A sample of nitrogen (Mr = 28.0) has a mass of 10 g and a
volume of 8 L. Which of the following values can be calculated
for the nitrogen sample from these data?
I moles II % w/v III density
A I only B I and II only
C I and III only D I, II and III
hello,
i was wondering what the answer to this question should be cause in the worked solution (funny enough didnt give any explaination of how they got their ans) got B but the back of the book said C and i said D???
thank you

Answer 1

mole
concentration
density

Answer 2

mole=mass/Mr --------------- u both mass and Mr
concentration= mole/volume --------- u have u can find mole and thus concentration
density=mass/volume ------------you have both mass and volume

Answer 3

btw what's % w/v ?

Answer 4

your book is right tho
it should be C

Answer 5

http://dl.clackamas.edu/ch105-04/wtvolpct.htm
according to this i see that for
%w/v to find you need, solute and solvent, so that u can have Solution
BUT u have only Nitrogen

Answer 6

thank you for helping, very much appreciated :) but can't the mass of nitrogen be the mass of solute?

Answer 7

but you do not have solvent right?

Answer 8

the volume that you are supposed to use in that formula is Volume of Solution
if there is no Solvent, then how can u has Solution?

Answer 9

isnt the solvent 8L?

Answer 10

Noooo lol
8 L is volume of Nitrogen itself :)

Answer 11

it could be volume of Solution if this volume of N was with for example mixed with water (water acts as solvent)

Answer 12

but its volume of N alone

Answer 13

have you learnt about dilution?

Answer 14

yes i have c1v1 = c2v2

Answer 15

see in dilution, its solute (which can be anything) and then u just add water to it to make up some amount of volume
in that case this volume that u made up is volume of Solution

Answer 16

thank you :)
i have another question though can u please help me here as well?
More energy is required to vibrate:
A C–C compared to C=C
B C–Cl compared to C–Br
C C–O compared to C–H
D C=C compared to C≡C

shouldn't the answer be B, the back of book says C?

Answer 17

well A and D are just too wrong, u understand why right?

Answer 18

yes cause triple bond is stronger than double bond which is stronger than single bonds

Answer 19

good :)
are you familiar with Electronegativity concept?

Answer 20

yes F most electronegative, electron attracting ability

Answer 21

okay so Cl is more electronegative then Br right?

Answer 22

yes

Answer 23

but Br is just below Cl right

Answer 24

Cl electronegativity values is 3.0
and Br is 2.8
and thus the difference is only 0.2 right?

Answer 25

electronegativity value for H is 2.1 and for O is 3.5
difference is 1.4

Answer 26

so what do you think which one requires highest amount of energy?

Answer 27

isnt it between c and cl or c and br not between cl and br?

Answer 28

C are going to stay same

Answer 29

so u focus on the one that changes

Answer 30

alright if u don't get it this way lets go with the way you get it

Answer 31

sorry

Answer 32

C is in group 4

Answer 33

u do know that electronegativity increases across the period right?

Answer 34

yes

Answer 35

so anything before C is less electronegative then C and anything after C is more electronegative then C

Answer 36

do u agree to this?

Answer 37

yes

Answer 38

next, u do know that electronegativity increases as u go UP the group
from the period 7 to period 1 going up it increases

Answer 39

yes

Answer 40

okay cool
now look
the bond is C-Cl and C-Br
Cl is is below and to the right of C
and Br is more below but same amount to the right

Answer 41

so that means it harder to break C-Cl bond the C-Br bond right?

Answer 42

yes so the ans is b?

Answer 43

now lets go back to electronegativities

C - 2.5 Cl- 3.0
C-2.5 Br- 2.8

Answer 44

u can understand why Cl is stronger right?

Answer 45

no, it is C

Answer 46

C- 2.5 O- 3.5
C- 2.5 H- 2.1

Answer 47

cause i always thought that we should look at it with the mass, the lighter the mass the harder to break the bond

Answer 48

difference in electronegativities between C-Cl is 3.0-2.5= 0.5
for C- Br 2.8-2.5= 0.3

and u see that difference in C-Cl is bigger
thus its stronger

Answer 49

no it's actually all about electronegativity

Answer 50

now when u look at C- O the difference is 3.5-2.5= 1
and for C-H its 2.1-2.5= -0.4

Answer 51

now tell me
difference between 0.5 and 0.3 OR difference between 1 and -0.4
is greater?

Answer 52

1

Answer 53

as u see the difference between C-H and C-O bond is way greater then in C-Cl and C-Br

Answer 54

thats why more energy is needed to break C-O then C-Cl

Answer 55

i hope i didn't confuse u even more, if i did please tell me

Answer 56

nope i got it now thank you i know it takes more to break c-o than c - cl but it takes more energy to break c-h than c-o right?

Answer 57

yes thats right! u compare the differences between elcetronegativities

Answer 58

difference between C- O and C-H was greater the difference between C-Cl and C-Br

Answer 59

thus C would be your right answer

Answer 60

yes i know... but just a side question: c-h requires more energy to break than c-o?

Answer 61

no no no lol C-O requires more energy

Answer 62

oh ok thank you :)

Answer 63

you are welcome :)