Another Phys with Calc problem

  • Thread starter Thread starter frankfjf
  • Start date Start date
Click For Summary
SUMMARY

The discussion revolves around calculating the mass of a water molecule (H2O) and estimating the number of water molecules in the world's oceans. A water molecule consists of two hydrogen atoms (1.0 u each) and one oxygen atom (16 u), resulting in a total mass of 18 u. The conversion from atomic mass units to kilograms is clarified, with the formula 1 u = 1/6.022 x 10^23 grams, leading to the conclusion that the mass of one water molecule is approximately 18/6.022 x 10^26 kilograms. This foundational understanding allows for straightforward calculations regarding the total number of water molecules in the oceans.

PREREQUISITES
  • Understanding of atomic mass units (u)
  • Basic knowledge of molecular composition
  • Familiarity with Avogadro's number (6.022 x 10^23)
  • Ability to perform unit conversions between grams and kilograms
NEXT STEPS
  • Research the concept of molar mass and its applications in chemistry
  • Learn about the significance of Avogadro's number in chemical calculations
  • Explore the methods for estimating the mass of other molecules
  • Investigate the distribution of water in Earth's oceans and its implications for environmental science
USEFUL FOR

Students studying chemistry or physics, educators teaching molecular composition, and anyone interested in understanding the calculations related to molecular mass and its applications in real-world scenarios.

frankfjf
Messages
166
Reaction score
0
Hey again all, this time my problem is how to start this problem:

One molecule of water (H2O) contains two atoms of hydrogen and one atom of oxygen. A hydrogen atom has a mass of 1.0 u and an atom of oxygen has a mass of 16 u, approximately. (a) What is the mass in kilograms of one molecule of water? (b) How many molecules of water are in the world's oceans, which have an estimated total mass of 1.4 × 1021 kg?

It's obvious that once I've got the answer to part a, part b is easy. However, my theory as to how to solve part a seems too simple to work. If I'm told that a molecule of water contains two hydrogen atoms and one oxygen atom, and that 1 hydrogem atom = 1 u whereas 1 oxygen atom = 16 u... is the answer to part a as simple as converting 18u to kilograms? Trying it that way seems to come up with an incredibly large decimal so I'm skeptical as to whether or not my theory is correct. Please help.
 
Physics news on Phys.org
I will give you an answer to first question. You have certainly seen the number 6.022*10^23. We get this number when we just divide 1g by u (in grams).
1/u=6.022*10^23
So if something weighs 18u it means that it weighs 18/6.022*10^23 grams. And that is 18/6.022*10^26 kilograms.
 
Last edited:

Similar threads

AC and Electrolysis
  • · Replies 11 ·
Replies
11
Views
1K
Finding recoil velocity of an object during a collision
  • · Replies 9 ·
Replies
9
Views
2K
Oscillation of free surface of water in parallelepiped container
  • · Replies 13 ·
Replies
13
Views
2K
Ball Lightning: Uncovering the Mystery of N_7^{14}, H_1^1, & O_8^{16}
  • · Replies 21 ·
Replies
21
Views
3K
Problem with molecular separation calculations
  • · Replies 5 ·
Replies
5
Views
2K
A runner weighs 687 N and 71% of this weight is water. (a) H
  • · Replies 6 ·
Replies
6
Views
3K
I try to solve a thermodynamics problem on heat transfer
  • · Replies 3 ·
Replies
3
Views
2K
How to solve multiple choice questions?
  • · Replies 4 ·
Replies
4
Views
20K
Why wasn't fluorine used as a standard for atomic mass?
  • · Replies 6 ·
Replies
6
Views
3K
Magnitude of the Net Electrostatic Force On an Oxygen Atom
  • · Replies 1 ·
Replies
1
Views
10K