It means “the study of.” Think of it:
Those are subjects you study. It makes more sense than the other choices.
Answer:
17.65 grams of O2 are needed for a complete reaction.
Explanation:
You know the reaction:
4 NH₃ + 5 O₂ --------> 4 NO + 6 H₂O
First you must know the mass that reacts by stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction). For that you must first know the reacting mass of each compound. You know the values of the atomic mass of each element that form the compounds:
- N: 14 g/mol
- H: 1 g/mol
- O: 16 g/mol
So, the molar mass of the compounds in the reaction is:
- NH₃: 14 g/mol + 3*1 g/mol= 17 g/mol
- O₂: 2*16 g/mol= 32 g/mol
- NO: 14 g/mol + 16 g/mol= 30 g/mol
- H₂O: 2*1 g/mol + 16 g/mol= 18 g/mol
By stoichiometry, they react and occur in moles:
- NH₃: 4 moles
- O₂: 5 moles
- NO: 4 moles
- H₂O: 6 moles
Then in mass, by stoichiomatry they react and occur:
- NH₃: 4 moles*17 g/mol= 68 g
- O₂: 5 moles*32 g/mol= 160 g
- NO: 4 moles*30 g/mol= 120 g
- H₂O: 6 moles*18 g/mol= 108 g
Now to calculate the necessary mass of O₂ for a complete reaction, the rule of three is applied as follows: if by stoichiometry 68 g of NH₃ react with 160 g of O₂, 7.5 g of NH₃ with how many grams of O₂ will it react?

mass of O₂≅17.65 g
<u><em>17.65 grams of O2 are needed for a complete reaction.</em></u>
<u>Given:</u>
Moles of CS2 (it cannot be CO2 as mentioned in the question, since O2 reacts with CS2 and not CO2) = 34.5 mol
<u>To determine:</u>
Moles of O2 undergoing the reaction
<u>Explanation:</u>
The reaction is-
CS2 + 3O2 → CO2 + 2SO2
Based on the stoichiometry: 3 moles of O2 reacts with 1 mole of CS2
therefore the moles of O2 that would combine with 34.5 moles of CS2 are
= 3 moles O2 * 34.5 moles CS2/1 mole CS2 = 103.5 moles
Ans: Around 104 moles of O2 would react with 34.5 moles of CS2
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