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Eduardwww [97]
3 years ago
11

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?

Chemistry
1 answer:
Scorpion4ik [409]3 years ago
3 0

You would have to dig up 261 g of sylvanite.

Mass of sylvanite = 73.0 g Au × (100 g sylvanite/28.0 g Au) = <em>261 g</em> sylvanite.


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If you had a 0.5 M KCl solution, how much solute would you have in moles, and what would the solute be?
Svetradugi [14.3K]

Answer:

37.25 grams/L.

Explanation:

  • Molarity (M) is defined as the no. of moles of solute dissolved per 1.0 L of the solution.

<em>M = (no. of moles of KCl)/(volume of the solution (L))</em>

<em></em>

∵ no. of moles of KCl = (mass of KCl)/(molar mass of KCl)

∴ M = [(mass of KCl)/(molar mass of KCl)]/(volume of the solution (L))

∴ (mass of KCl)/(volume of the solution (L)) = (M)*(molar mass of KCl) = (0.5 M)*(74.5 g/mol) = 37.25 g/L.

<em>So, the grams/L of KCl = 37.25 grams/L.</em>

6 0
3 years ago
Using the following reaction (depicted using molecular models), large quantities of ammonia are burned in the presence of a plat
Mila [183]

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 O_{2} =\frac{7.5 g of NH_{3} * 160 g of O_{2} }{68 g of NH_{3} }

mass of O₂≅17.65 g

<u><em>17.65 grams of O2 are needed for a complete reaction.</em></u>

3 0
3 years ago
Sighting along the C2-C3 bond of 2-methylbutane, the least stable conformation (Newman projection) has a total energy strain of
natima [27]

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!

3 0
3 years ago
Calculate the density of a solid that has a volume of 2cm3 and a mass of 3g
katrin2010 [14]

Answer:

The density is 6

Explanation:

p = m × v

p = 3 × 2

p = 6

Hope this helped! :)

8 0
3 years ago
Is aluminum a liquid at 1000 kelvin
daser333 [38]
Yes you are correct
3 0
3 years ago
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