December 30, 2024, 05:45:22 PM
Forum Rules: Read This Before Posting


« previous next »
Pages: [1]   Go Down

Topic: significant figures  (Read 4046 times)

0 Members and 1 Guest are viewing this topic.

Offline Moss

  • Regular Member
  • ***
  • Posts: 20
  • Mole Snacks: +0/-0
significant figures
« on: September 21, 2009, 05:57:52 AM »
hey
N2H4 + O2 --> N2 + 2H2O

DETERMINE WHICH IS IN EXCESS AND BY HOW MANY GRAMS

oxygen is in excess.

find how many grams

n(N2H4) = 2.29/ ( 2*14.01 + 4*1.01)
=0.071..

m(O2)= 0.071.. *32
=2.2857..

3.14-2.2857.. =0.854g

but the answer says 0.853g... this is really irritating me

please help
thanks
Logged

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27891
  • Mole Snacks: +1816/-412
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: significant figures
« Reply #1 on: September 21, 2009, 06:16:25 AM »
State clearly what was the question, nobody is going to reverse engineer your answer to guess what was the original data.
Logged
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Moss

  • Regular Member
  • ***
  • Posts: 20
  • Mole Snacks: +0/-0
Re: significant figures
« Reply #2 on: September 21, 2009, 06:22:30 AM »
hydrazine is used in rocket fuel. it reacts with oxygen as follows:

N2H4 + O2 --> N2 + 2H2O

in a particular rocket engine,2.29g of hydrazine and 3.14g of oxygen are available for reaction.
DETERMINE WHICH IS IN EXCESS AND BY HOW MANY GRAMS.
Logged

Offline kimyaa2

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +1/-0
Re: significant figures
« Reply #3 on: September 21, 2009, 07:07:52 AM »
the answere is so close to what you get..not a big deal..maybe there are some sig fig problems from the begining ..
Logged

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27891
  • Mole Snacks: +1816/-412
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: significant figures
« Reply #4 on: September 21, 2009, 07:25:04 AM »
Most likely they used slightly different molar mass of hydrazine - your is 32.06, exact one is 32.0452.

But in this case giving answer with accuracy better than 0.85g is absurd.
Logged
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info
Pages: [1]   Go Up
« previous next »
Sponsored Links