Sylvanite is a mineral that contains 28.0% gold by mass. How much sylvanite would you need to dig up to obtain 73.0 g of gold?
1 answer:
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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>
Answer:
21 KJ/mol
Explanation:
For this question, we have to start with the <u>linear structure</u> of 2-methylbutane. With the linear structure, we can start to propose all the <u>Newman projections</u> keep it in mind that the point of view is between carbons 2 and 3 (see figure 1).
Additionally, we have several <u>energy values for each interaction</u> present in the Newman structures:
-) Methyl-methyl <em>gauche: 3.8 KJ/mol</em>
-) Methyl-H <em>eclipse: 6.0 KJ/mol</em>
-) Methyl-methyl <em>eclipse: 11.0 KJ/mol</em>
-) H-H <em>eclipse:</em> 4.0 KJ/mol
Now, we can calculate the energy for each molecule.
<u>Molecule A</u>
In this molecule, we have 2 Methyl-methyl <em>gauche </em>interactions only, so:
(3.8x2) = 7.6 KJ/mol
<u>Molecule B</u>
In this molecule, we have a Methyl-methyl <em>eclipse </em>interaction a Methyl-H <em>eclipse </em>interaction and an H-H <em>eclipse</em> interaction, so:
(11)+(6)+(4) = 21 KJ/mol
<u>Molecule C</u>
In this molecule, we have 1 Methyl-methyl <em>gauche </em>interaction only, so:
3.8 KJ/mol
<u>Molecule D</u>
In this molecule, we have three Methyl-H <em>eclipse </em>interaction, so:
(6*3) = 18 KJ/mol
<u>Molecule E</u>
In this molecule, we have 1 Methyl-methyl <em>gauche </em>interaction only, so:
3.8 KJ/mol
<u>Molecule F</u>
In this molecule, we have a Methyl-methyl <em>eclipse </em>interaction a Methyl-H <em>eclipse </em>interaction and an H-H <em>eclipse</em> interaction, so:
(11)+(6)+(4) = 21 KJ/mol
The structures with higher energies would be less stable. In this case, structures B and F with an energy value of 21 KJ/mol (see figure 2).
I hope it helps!
