# Chemistry

Let's do 1 and 2 and go from there. I will get you started.
Take a 100 g sample.
That means we have
19.9% C = 19.9 g C
46.7% N = 46.7 g N
6.67% H = 6.67 g H
26.7% O = 26.7 g O
Find mols of these amounts.

mols C = 19.9/12 = 1.66
mols N = 46.7/14 = 3.33
mols H = 6.67/1 = 6.67
mols O = 26.7/16 = 1.67

To determine the empirical formula (it will be in small whole numbes), divide the smallest number of moles by itself (thereby forcing that to be 1.00), then to keep everything equal, divide all the other numbers by the same thing. The small whole numbers you obtain will be the empirical formula.

To determine the molar mass, use the boiling point constant.
delta T = Kb m
delta T is the difference between the normal boiling point of benzene and the boiling point of the solution of unknown and benzene. Kb is the benzene boiling point constant, and m is the molality of the solution. Calculate m.
Knowing that molality = # mols/kg solvent you can calculate # mols.
Knowing # mols=grams/molar mass you can calculate molar mass.

Post your work if you get stuck. If you don't know how to get started on 3 and 4, tell us what you don't understand about.

Determine the forumula and molecular mass for an organic compound from this information:
-5.00g of the organic solid was dissolved in 100.0g of benzene.
-Boiling point of solution was 82.3 degrees Celsius.
-The organic compound is 46.7% nitrogen, 6.67% hydrogen, 26.7% oxygen, and the remainder is carbon.
-The boiling temperature of pure benzene is 80.2 degrees C; Kb = 2.53 degrees CKg/mol

1. determine the molecular mass of the organic solid
2. determine the molecular formula of organic solid
3. determine the mole fraction of the organic solid in solution
4. if density of solution is 0.8989 g/ml, calculate molarity of solution.

This is what I got:

molecular formula: CN2H4O
molecular mass: 1.21 x 10^3

I got the molecular mass by subtracting 80.2 from 82.3 to get delta T which is 2.1 degrees celsius.
molality = delta T/kb=2.1/2.53=0.83 molal
mol = molal x kg= 0.83 x .005 kg=.00415 mol
mol = g/M therefore M=g/mol = 5/.00415 = 1205 M = 1.21 x 10^3 M

is that correct?

The empirical formula is correct. Good work. The molar mass is not quite right but almost. 0.83 molal is ok.
BUT, when I said molality = mols/kg I guess I SHOULD have said kg solvent but I assumed you would know you didn't use sample weight for BOTH g and kg solvent. You used kg of the sample as 0.005 and not 0.1 (for 100 g benzene solvent).
When you redo that one small part you will have CLOSE to (but not exact) molar mass. To find the exact molar mass is a 2-3 step procedure.
1. Add atomic masses of CN2H4O to obtain the exact mass of the empirical formula.
2. Divide the approximate molecular mass by what you have in #1. You should get very close to a whole number.
3. That whole number will be the number of units to multiply the empirical formula by. Usually these things are 1, 2, or 3.
4. Then recalculate the molecular mass from the molecular formula.

ok so now I got mol=molal x kg = 0.83 x 0.1 = 0.083 mol
M = 5.00g/0.083 mol = 60.24 = 60.2...when tryying to find the exact molar mass, the whole number was 1.002 which is very close to one so I just left it as 60.02...i think that should be right.
I need the molecular formula not the empirical formula, but when i divide the approximate molecular mass buy the exact, it's 1.002 so wouldn't the molecular formula and empirical formula be the same in this case?

i don't know give me the answer

1. 👍 0
2. 👎 0
3. 👁 119
1. yes it would

1. 👍 0
2. 👎 0

## Similar Questions

1. ### Social studies

What conclusion can be made about the british policy of assimilation? That it started because of settlement. That it started because of respect toward different culture. That it started because of exploration. That it started

asked by LOVE on February 2, 2016
2. ### probability

Mr. Spark has problems starting his two cars during the winter. He decided to record the number of times each car starts during a 30-day period. He recorded the following information. His Hyundai started 18 times. His Subaru

asked by jj reddick on November 4, 2010
3. ### English

1. In three minutes, he started to shout. 2. After three minutes, he started to shout. (Which preposition should we use? Which one is right?) 3. Three minutes later, he started to shout. 4. Some minutes later, he started to shout.

asked by rfvv on October 7, 2013
4. ### English

plz help me on this 1. What was the rumor about how "The Great Fire started? a. It was started to burn the germs from the plague b. A careless vagrant started it c. The French started it d. It started with the burning of the dead

asked by Soha on August 6, 2008
5. ### statistics

According to the Smart magazine, 70% of smokers started smoking before the age of 18. Suppose 10 smokers are randomly selected and the number of smokers who started to smoke before the age of 18 is recorded. a) explain why this is

asked by jerry on February 7, 2011
6. ### Creative

the level of excitement was getting higher and higher as the day went on. it was just us 4 kids at home waiting anxiously for some news of the baby the day seemed to stretch on forever, ... because there was nothing to do but wait

asked by y912f on October 12, 2009
7. ### English 12

I need help on an essay. I'm suppose to pick an author to write about and I chose Ernest Hemingway. I need help getting started. I need help on my thesis that way I can get started. Please Help and Thank you

asked by anoymous on November 9, 2011
8. ### History

Which most accurately describes the rise of the Arab Empire? the Arab empire started in Egypt and soon conquered lands to the southwest, including Sudan, Ethiopia, and Somalia the Arab empire started in Arabia and soon conquered

asked by malia on October 8, 2017
9. ### Physics

A kid slides down an icy (frictionless) hill starting from res. At the top his gravitational potential energy is 500J. Suppose after reaching the bottom he then continues sliding up another icy slope on the other side of the

asked by Tarissa on July 29, 2011
10. ### English

1. With night coming on, we started for home. 2. Because night came on, we started for home. 3. Night came on, and we started for home. -------------------------- Q1: Does #1 mean #2 or #3? Q2: What is the meaning of 'com on'?

asked by rfvv on August 24, 2016
11. ### english

How can I write a 8-12 paragraph essay describing the duties of a woman assisting her boss in a company doing everyday activities.I am having trouble gettig started. This is ficticious for a class I am taking. HELP!!!!!Can you get

asked by debbie on April 3, 2010

More Similar Questions