Biology; Chemistry; Physics: Post your doubts here!

[daredevil]

what is meant by FIDUCIAL AID?? it is in relation to physics atp. in some notes my sir gave me. i looked it up in the dictionary for fiducial and it said:
"(esp. of a point or line) assumed as a fixed or basis for comparison.
please can anyone elaborate on it??
it is mostly used in ray diagrams i gues... if that helps/ :|

 

[Fallen316]

what is meant by FIDUCIAL AID?? it is in relation to physics atp. in some notes my sir gave me. i looked it up in the dictionary for fiducial and it said:
"(esp. of a point or line) assumed as a fixed or basis for comparison.
please can anyone elaborate on it??
it is mostly used in ray diagrams i gues... if that helps/ :|

(Physics / General Physics) ​

Physics​

used as a standard of reference or measurement​

 

[SilverCrest]

5070 s2005 p1
9 How many moles per dm3 of gaseous carbon dioxide are there if 4.4 g occupies 500 cm3?
A 0.1 mol / dm3 B 0.2 mol / dm3 C 2.2 mol / dm3 D 8.8 mol / dm3

the answer is B..how??

 

[SilverCrest]

what is meant by FIDUCIAL AID?? it is in relation to physics atp. in some notes my sir gave me. i looked it up in the dictionary for fiducial and it said:
"(esp. of a point or line) assumed as a fixed or basis for comparison.
please can anyone elaborate on it??
it is mostly used in ray diagrams i gues... if that helps/ :|

for example when u r counting the periods of oscillation for a pendulum....u can stand a marker at the start of the swing..to help you know when each period is over!

 

[asd]

and ayeshaK and asd but howw??? why can't H+ ions be most in number?? it IS an aquesous solution after all. that is what's confusing me

Water dissociates into H+ and OH- . So There can't be 2 H+ ions since only one H atom forms the Positive Ion, while the other stays with oxygen to from OH-

 

[SilverCrest]

5070 s2005 p1
9 How many moles per dm3 of gaseous carbon dioxide are there if 4.4 g occupies 500 cm3?
A 0.1 mol / dm3 B 0.2 mol / dm3 C 2.2 mol / dm3 D 8.8 mol / dm3

the answer is B..how??

please need help quickly!

 

[daredevil]

Water dissociates into H+ and OH- . So There can't be 2 H+ ions since only one H atom forms the Positive Ion, while the other stays with oxygen to from OH-

yeah but they didn't tell us the amount of water so how do we know that there is lesser water in there so lesser H+ ions than Na+ ions will b formed. sorry for the nagging ... i just can't stop until i get it al cleared

 

[A star]

please need help quickly!

4.4g/(32+12)= 0.1mole and 0.1mole/0.5dm3 gives 0.2mol/dm3

 

[A star]

yeah but they didn't tell us the amount of water so how do we know that there is lesser water in there so lesser H+ ions than Na+ ions will b formed. sorry for the nagging ... i just can't stop until i get it al cleared

can you repeat ur question so i can help. i cannot find it

 

[daredevil]

please need help quickly!

is the answer 0.2mol/dm3 for the first one??

 

[A star]

is the answer 0.2mol/dm3 for the first one??

i think she already told that

 

[SilverCrest]

4.4g/(32+12)= 0.1mole and 0.1mole/0.5dm3 gives 0.2mol/dm3

oh thanks. .i was using the formula wrong!

 

[Dukeofwin]

4.4g/(32+12)= 0.1mole and 0.1mole/0.5dm3 gives 0.2mol/dm3

Where did you get 32 from?
Shouldn't the Mr be 18?
Moles=Mass/Mr
4.4/18=0.2moles
Answer is same Why?

 

[asd]

yeah but they didn't tell us the amount of water so how do we know that there is lesser water in there so lesser H+ ions than Na+ ions will b formed. sorry for the nagging ... i just can't stop until i get it al cleared

did they tell you the amount of sodium sulfate? They didn't either. Just the concentration (the no. of moles in 1 dm3). What do you expect will the concentration of water be? It's just water.

 

[Dukeofwin]

please need help quickly!

I got Moles=Mass/Mr
4.4/18=0.2 moles!
What formula are you guys using?

 

[SilverCrest]

I got Moles=Mass/Mr
4.4/18=0.2 moles!
What formula are you guys using?

mr of CO2
12+16+16=44
no.of moles=4.4/44=0.1
molar conc=moles/volume
0.1/0.5=0.2 mol/dm3

hope that clears it up!

 

[Dukeofwin]

mr of CO2
12+16+16=44
no.of moles=4.4/44=0.1
molar conc=moles/volume
0.1/0.5=0.2 mol/dm3

hope that clears it up!

Thanks, 18 Mr is of H20!
Sorry abt that!

 

[ashiqbal]

and ayeshaK and asd but howw??? why can't H+ ions be most in number?? it IS an aquesous solution after all. that is what's confusing me

it is 2 mol/dm3, and this is indeed very high concentration of sodium sulphate!! so very less H+ and OH- ions! plus the thing about the number of sodium and sulphate ions dissociated cancels out sulphate as well!

 

[ayeshaK]

http://www.xtremepapers.com/papers/...nal O Level/Physics (5054)/5054_s10_qp_41.pdf
Question 2 ci)
Can anybody confirm !! Ihave made it ! Just wanna confirm

 

[a.abid]

http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Physics (5054)/5054_s10_qp_41.pdf
Question 2 ci)
Can anybody confirm !! Ihave made it ! Just wanna confirm

It will be a slant line upto 100m after which it will be a straight one...the same graph as the one i told u earlier today...