Chemistry Homework: 2H2+O2 Reaction, Limiting Reactant, Heat & H2O

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Discussion Overview

The discussion revolves around a chemistry homework problem involving the reaction of hydrogen and oxygen to produce water, specifically focusing on calculating the grams of hydrogen required for a given amount of heat, determining the limiting reactant, and the mass of water produced. The scope includes mathematical reasoning and conceptual clarification related to stoichiometry and energy in chemical reactions.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant asks how many grams of H2 are needed to produce 2.21x103 kJ of heat and how this relates to the reaction 2H2 + O2 = 2H2O + 242 kJ.
  • Another participant emphasizes the importance of showing working to receive help and encourages the original poster to think through the problem.
  • A participant suggests using the ratio of moles in the chemical equation to find the mass of H2 needed for the desired energy output.
  • There is a question about whether to multiply the mass of H2 by 2210 and a clarification that 2 refers to the number of moles, not the mass.
  • Another participant confirms that the mass of H2 is related to the moles and encourages using a periodic table to assist with calculations.

Areas of Agreement / Disagreement

The discussion does not reach a consensus, as participants provide varying levels of assistance and clarification without resolving the original poster's questions or confirming specific calculations.

Contextual Notes

Participants express uncertainty about the calculations and the application of stoichiometric ratios, indicating a need for further clarification on the relationship between moles, mass, and energy in chemical reactions.

Who May Find This Useful

Students seeking help with stoichiometry, limiting reactants, and energy calculations in chemical reactions may find this discussion beneficial.

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2H2+O2=2H2O+242kJ (HEAT)
-How many grams of H2 gas are required to produce 2.21x103 kJ of heat?
-How many grams of H2 gas are required to react with 785 gm of O2 gas?
-If 300 gms of O2 gas and 75 gms of H2 gas are mixed and burned what is the limiting reactant?
-How many grams of H2O are produced in question above?

please help
 
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Welcome to the forums. Please note that you are required to show working before we can help you. So, do you have any thoughts?
 
help

cristo said:
Welcome to the forums. Please note that you are required to show working before we can help you. So, do you have any thoughts?

i have no idea
 
Remember that everything in a chemical equation is a ratio, including energy.

If 2 moles of H2 gives you 242kJ, what mass of H2 gives you 242kJ? Now what mass of H2 do you need for your desired amount of energy?
 
do i multiply H2 mass by 2210? is 2 the mass of H2?
 
Yes the mass of H2 is 2, don't you have a periodic table of elements? What TMM was trying to say is that if you have 2 moles of H2 that gives 242 KJ. How many moles would give you 2.21x103 kJ. It's just a simple ratio
 
thank u, TMM and ace123
 

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