Solve Mass Fraction Problem: 100g H2O, 11.2g H, 3.06g H2

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Discussion Overview

The discussion revolves around a homework problem involving the mass of water produced from a given mass of hydrogen gas (H2) reacting with oxygen. Participants explore the relationships between the masses of hydrogen and water, as well as the distinction between elemental hydrogen (H) and molecular hydrogen (H2).

Discussion Character

  • Homework-related, Conceptual clarification

Main Points Raised

  • One participant expresses confusion about the distinction between 11.2 g of H and 3.06 g of H2, questioning why both are not referred to as H2 or H.
  • Another participant attempts to calculate the mass fraction of hydrogen in water and subsequently estimates the mass of water that could be produced from 3.06 g of H2, arriving at a value of 27.3 g of H2O.
  • There is a question raised about whether the mass of 3.5 g of H is different from the mass of 3.5 g of H2, and whether they differ in the number of hydrogen atoms.
  • One participant initially states that the masses are not the same but later corrects themselves, indicating that they are the same and do not differ in terms of the number of hydrogen atoms.

Areas of Agreement / Disagreement

The discussion contains some confusion and disagreement regarding the distinction between elemental hydrogen and molecular hydrogen, as well as the calculations related to the mass of water produced. There is no clear consensus on the correctness of the calculations presented.

Contextual Notes

Participants express uncertainty about the relationships between the masses of H and H2, and the implications for the number of hydrogen atoms involved. The calculations presented rely on specific assumptions about the mass fraction and stoichiometry that are not fully resolved.

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Homework Statement


If 100 g H2O contains 11.2 g H, what mass of water could be obtained from 3.06 g H2(g) reacting with an excess of O2(g)?

Homework Equations


Mass % of X in a sample= (Mass of X in sample/ Mass of the sample)*100


The Attempt at a Solution


The parts that confused me were 11.2g of H and the 3.06g H2. Why aren't both be H2 or H? Can anyone help me with this problem? THank you in advance.

This is my effort:
I look for the mass fraction of H in 100g of H2O:
11.2g of H/100g H2O= .112

Then, I find the Mass of H2O
3.06g/.112 = 27.3g H2O

Is this correct?
 
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lucky_star said:
The parts that confused me were 11.2g of H and the 3.06g H2. Why aren't both be H2 or H?

Is mass of 3.5 g of H different from the mass of 3.5 g H2? Do they differ in number of atoms of hydrogen?

This is my effort:
I look for the mass fraction of H in 100g of H2O:
11.2g of H/100g H2O= .112

Then, I find the Mass of H2O
3.06g/.112 = 27.3g H2O

Is this correct?

Yes.
 
Is mass of 3.5 g of H different from the mass of 3.5 g H2? Do they differ in number of atoms of hydrogen?
No, they are not the same. I understand it now.

Thank you Borek!
 
lucky_star said:
No, they are not the same. I understand it now.

Oops, not good. They ARE the same and they DON'T differ in terms of the number of hydrogen atoms.
 
Oh, Thanks again :)
 

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