Thursday, February 19, 2009
INTENSE!!!
I can't believe i slept the whole afternoon after i reach home! DIE! i wasted my time, and later i have to go mr ho! AND I HAVE NOT STUDIED PHYSICS! LENSES!. My physics cannot cmi again already, i must make it nah! And, my english compre improve! wooho. Hope dont have to go el srp. And i hope no Cl srp, and no Physics srp. If physics srp does not falls on wed, i would go, but, it falls on wed! tmr will know who would be going for srp.
Chem test was.. HAHASS! i did some of them during mr ho! And that woman actually copied the whole question, the whole chunk in! except the ammonia part. GRR.... And i still dont know what the hell is... relative abundance. searched the net.. and what i got is...,
How can you calculate the relative abundance of two isotopes when given the atomic masses of both isotopes and also the average atomic mass for the element?
Igloo says The conventional method is to use algebra. Let’s take an example. Copper consists mainly of two isotopes, 63Cu and 65Cu, and its (average) atomic mass is 63.55 (to 2 d.p.) Let’s assume next that the percentage abundance of 63Cu is x This means that the percentage abundance of 65Cu will be 100-x Given 100 random copper atoms, x will each have a mass of 63 [total mass = 63x] And 100-x will have a mass of 65 [total mass = (100-x) x 65 = 6500-65x] So the total mass of 100 atoms = 63x + 6500–65x = 6500–2x This means that the average mass = (6500–2x) / 100 But we are told in the question that average mass = 63.55 Therefore (6500-2x) / 100 = 63.55 So 6500–2x = 6355 Hence 2x = 6500-6355 = 145 And x = 72.5 So, in a typical sample of copper 72.5% of the atoms are 63Cu and 27.5% are 65Cu.
and... i don't even understand a single part of it.
GEOG TEST= no hope, didn even prepare the least...
I can't believe i slept the whole afternoon after i reach home! DIE! i wasted my time, and later i have to go mr ho! AND I HAVE NOT STUDIED PHYSICS! LENSES!. My physics cannot cmi again already, i must make it nah! And, my english compre improve! wooho. Hope dont have to go el srp. And i hope no Cl srp, and no Physics srp. If physics srp does not falls on wed, i would go, but, it falls on wed! tmr will know who would be going for srp.
Chem test was.. HAHASS! i did some of them during mr ho! And that woman actually copied the whole question, the whole chunk in! except the ammonia part. GRR.... And i still dont know what the hell is... relative abundance. searched the net.. and what i got is...,
How can you calculate the relative abundance of two isotopes when given the atomic masses of both isotopes and also the average atomic mass for the element?
Igloo says The conventional method is to use algebra. Let’s take an example. Copper consists mainly of two isotopes, 63Cu and 65Cu, and its (average) atomic mass is 63.55 (to 2 d.p.) Let’s assume next that the percentage abundance of 63Cu is x This means that the percentage abundance of 65Cu will be 100-x Given 100 random copper atoms, x will each have a mass of 63 [total mass = 63x] And 100-x will have a mass of 65 [total mass = (100-x) x 65 = 6500-65x] So the total mass of 100 atoms = 63x + 6500–65x = 6500–2x This means that the average mass = (6500–2x) / 100 But we are told in the question that average mass = 63.55 Therefore (6500-2x) / 100 = 63.55 So 6500–2x = 6355 Hence 2x = 6500-6355 = 145 And x = 72.5 So, in a typical sample of copper 72.5% of the atoms are 63Cu and 27.5% are 65Cu.
and... i don't even understand a single part of it.
GEOG TEST= no hope, didn even prepare the least...
what we could have been, 5:34 PM.
