﻿ Chemistry HELP! - Page 2

1. Originally Posted by DarkSnow @Blizzard OMG.. You GENIUS. Thank you so much T_T
I have a question though, do the forumlas I've highlighted only work when the volume is given in dm-3? Or can they also work when the information is given in cm-3?

Also, I used the formulas you gave me (which made a lot of sense and I'm wondering why my teacher didn't give us those), for question 6 C and it made a lot of sense (of the same exercise and that I had left blank since I did not understand it), however, I also left question 5 C (ex. 1.5) and I can't figure that one out, could you please help me?
I can explain but I can't do all of them. Secondly, cm3 will also work with all these formulas, or any unit of volume for that fact, its just that the concentration was given in mol dm-3, so I converted everything to dm3. You have to make sure the units are same before doing ANY calculation.  Reply With Quote

2. The percentage composition by mass of a hydrocarbon is C = 85.6% and H = 14.4%.
(a) Calculate the empirical formula of the hydrocarbon.  Reply With Quote

3. Originally Posted by DarkSnow The percentage composition by mass of a hydrocarbon is C = 85.6% and H = 14.4%.
(a) Calculate the empirical formula of the hydrocarbon.
I didn't have to answer that; http://answers.yahoo.com/question/in...5205520AAMLOER If you don't understand just tell me, I will elaborate.  Reply With Quote

4. @Blizzard
What is the mass, in g, of one molecule of ethane, C2H6?  Reply With Quote

5. Originally Posted by DarkSnow @Blizzard
What is the mass, in g, of one molecule of ethane, C2H6?
1. Find Molar Mass:
Mass of C * 2
Mass of H * 6

2.
Mass in g x : Molar Mass
1 molecule : 6.23 * 1023

Ans: Mass in g = Molar Mass / 6.23 * 1023

Solve it and tell me the answer, I'll confirm if it is right or wrong.  Reply With Quote

6. I remember doing this in year 12... so awesome when you know how to get the answer   Reply With Quote

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•