兩條f.6 chem

陳小吉

1:在0攝氏度和760mmHG下 一公升氧的質量為1.43g。計算在23攝氏度和720mmHG下,一公升氧的質量。 ans:1.25g


2:在17攝氏度和740mmHG下 氧的體積為21.5cm^3。 翌日發現氧的體積是22.1cm^3 而壓強仍然保持在740mmHG 問實驗室的溫度是多少?   ans:298k



唔該用中文答同埋詳細列式=0=唔該

[ 本帖最後由 陳小吉 於 21-9-2008 15:51 編輯 ]

piyopiyo

PV=nRT
(720/760)=n(0.0825)(296)
n=0.039mole
32(0.039)=1.25
-------------
PV=nRT
(740/760)(21.5/1000)=n(0.0825)(290)
n=8.75x10^-4mole
----
PV=nRT
T=298k

陳小吉

原帖由 piyopiyo 於 21-9-2008 18:36 發表
PV=nRT
(720/760)=n(0.0825)(296)
n=0.039mole
32(0.039)=1.25
-------------
PV=nRT
(740/760)(21.5/1000)=n(0.0825)(290)
n=8.75x10^-4mole
----
PV=nRT
T=298k

紅字果度  個常數唔係8.314咩?點解變左0.0825

可唔可以列條式係用8.314黎計

piyopiyo

原帖由 陳小吉 於 21-9-2008 20:40 發表

紅字果度  個常數唔係8.314咩?點解變左0.0825

可唔可以列條式係用8.314黎計

R=8.314 is used when P is expressed in Pa....
R=0.0825 is for P expressed in atm

Zend

just change mmHg to Pa

101325 Pa = 760mmHg

倉鼠傑～＊

gas constant in atm= 0.08205 < am i wrong?
gas constant in Pa = 8.314
How about mmHG's gas constant?
i tried PV=nRT , (720/760)(101325) = n (8.314)(273) , n= 42.29...
in fact i dont understand the conversion of unit -_____-"

Puppet

原帖由 陳小吉 於 21-9-2008 15:49 發表
1:在0攝氏度和760mmHG下 一公升氧的質量為1.43g。計算在23攝氏度和720mmHG下,一公升氧的質量。 ans:1.25g


2:在17攝氏度和740mmHG下 氧的體積為21.5cm^3。 翌日發現氧的體積是22.1cm^3 而壓強仍然保持在740mmHG  ...

PV = nRT
PMV = mRT

M, V and R are constants.
=> P1/m1T1 = P2/m2T2

The only must for units is T in K.
Just plug in mmHg, which is fine.

Zend

原帖由 倉鼠傑∼＊ 於 22-9-2008 07:10 AM 發表
gas constant in atm= 0.08205 < am i wrong?
gas constant in Pa = 8.314
How about mmHG's gas constant?
i tried PV=nRT , (720/760)(101325) = n (8.314)(273) , n= 42.29...
in fact i dont understand the ...

1公升係1dm^3 唔係1m^3

請全部用番SI unit

P=> Pascal(N m^-2)
V (m^3)
n ( mol)
R (J mol^-1 K-1 )
T (K)

PV=nRT

piyopiyo 只係用known fact

P = 1atm
V = 22.4 dm^3
n= 1
T = 273
佢個R 會係22.4/273
=0.08205(個unit 會變左 atm dm^3 K^-1 mol^-1 )

但我唔會鼓勵這樣做

piyopiyo

原帖由 倉鼠傑∼＊ 於 22-9-2008 07:10 發表
gas constant in atm= 0.08205 < am i wrong?
gas constant in Pa = 8.314
How about mmHG's gas constant?
i tried PV=nRT , (720/760)(101325) = n (8.314)(273) , n= 42.29...
in fact i dont understand the ...

I also worked out that R in atm = 0.08205...
but the notes states that it is 0.0825,it is ptless to waste the time bothering about that[[tk_02]]

Zend

shame on you, piyopiyo[[tk_02]]