# Question bout physical chem

1. May 31, 2005

### siewwen168

1) The space vehicle,Gemini,started its journey in space with 322kg of liquid
fuel, CH3NHNH2. This fuel is oxidised by dinitrogen tetroxide,N2O4,to form
nitrogen,carbon dioxide and water.hat is the mass of N2O4,in kg,that is
required to oxidiese all the fuel?
(A) 258
(B) 644
(C) 805
(D) 875 *
(E) 161
The answer i got is c,but actual is d,is there anything wrong bout my calculations??can anyone show me???

2) Which of the following contains 1 mol of the particles stated?
(A) Chlorine molecules in 35.5g of chlorine gas
(B) Electrons in 1g of hydrogen gas *
(C) Hydrogen ions in 1dm3 of 1 moldm-3 aqueous sulphuric acid
(D) Oxygen atoms in 22.4dm3 of oxygen gas at s.t.p

thanks alot for anyone who help :tongue2:

Last edited: May 31, 2005
2. Jun 2, 2005

### gravenewworld

How many moles is this?

can you write out the balanced reaction that is taking place? Do these 2 steps and you should be able to get the answer. If not post what work you have done.

Once again calculate moles.

For A how many moles is 35.5g of Cl2 gas? 1 mole of Cl2 has 2 moles of Cl molecules.
b) how many moles is 1g of H2 gas? there are 2 e- in 1 mol of H2 gas....
etc.....

3. Jun 3, 2005

### siewwen168

hi,actually from my calculation of the first question,the mass of N2O4 that i got is 805kg,but the answer given is 875kg.i don;t think that i have anything wrong in my calculations,so i need your answer.Because those question got alot of mistakes,haha,maybe i'm just lying to myself.but pls,can u give me your answer??? :yuck:

Before i proceed,i have to apologize first because i got more question to trouble u.so sorry bout that.
1) Explain why carbon-12 replaced oxygen as a standard in the determination of relative atomic mass???(or why it used as a standard in determining Ar?)
Is it because carbon-12 is more available compared to oxygen,and it's easier to transport than oxygen.this is my answer,but i don;t know whether correct or not.it sounds stupid,right??? :tongue:

2) Haemoglobin is a protein which carries oxygen in the red blood cell. Each
molecule of haemoglobin contains 4 iron atoms.If 1g of haemoglobin contains 0.00341g of iron ,calculate the RMM of haemoglobin.

3) The density of ice is 1.00gcm-3.What volume of steam is produced when 1cm3 of ice is heated to 323degree celcius(596K) at a pressure of 1 atm.(101kPa)? (1 mol gas occupies 24.0dm3 at 25 degree celcius and 1 atm.)

Till here,that's all. I think there are more.sorry for that.u may think that i;m lazy to solve my own problem,but i did try,at last,i can't get it.therefore,i need someone to help.anyway,thanks alot for your help. :tongue2:

4. Jun 3, 2005

### gravenewworld

The balanced equation is:
CH3NHNH2 +(5/4)N204-----> (9/4)N2+CO2+3H20
I don't have a periodic table so you have to plug in what the values are...

322kg fuel x (1000gfuel/1kgfuel) x (1 mol fuel/mw of fuel) x (5/4 mol N204/1mol fuel) x (mw of N204/1mol N204)= units cancel and you get your answer in g of N204, you just need to fill in the 2 molecular weights. The answer asks for amount of N204 in kgs so just divide your answer by 1000

5. Jun 3, 2005

### gravenewworld

These are all the same types of problems

1) instead of me typing this website explains-http://dl.clackamas.cc.or.us/ch104-03/changes.htm [Broken]

2.)It says the ratio of molecules of Fe to a molecule of hemoglobin is 4:1. How many moles of Fe is 0.00341g of iron? Divide this by 4 and you have the number of moles of hemoglobin. Thus you know 1g is X moles of hemoglobin from that you should be able to find mw of hemoglobin

3.) how many moles of water is 1cm^3 of ice? figure that out and use PV=nRT

Last edited by a moderator: May 2, 2017
6. Jun 6, 2005

### siewwen168

question again.

thanks bout the answer for changes in standard.

for second question ,0.00341g of iron have 0.00341/26 moles of iron atoms ,right?the answer will then divided by 4 because 1 molecule of haemoglobin contain 4 atoms of iron.1g of haemoglobin will contain the moles that i count,then 1g will be divided by the answer,and the relative molecular mass of haemoglobin will be known.i got 30498.5 but the answer is 65454,why???

For the third question, 1 cm^3 of ice is 1/18 mole of ice,right???Then,pV=nRT,
V=nRT/p
=(8.31x1/18x596)/(101x10^3)
=2.72x10^-3 m3
*the answer given is 2.67 dm3,when i convert my answer,it's wrong ,why???

anyway,thanks alot for helping me so much :tongue2: