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Ray Of Light [21]
3 years ago
5

Out of 500 silicon atoms: 460 are si-28, which has a mass of 27.98 amu 25 are si-29, which has a mass of 28.98 amu and 15 are si

-30, which has a mass of 29.97 amu. what is the average atomic mass of silicon? (round to 2 decimal places) (hint: they did not give you percentages, but you can calculate the percentages and then do the problem)
Chemistry
2 answers:
exis [7]3 years ago
7 0

Average mass can be calculated by taking average of mass of each isotopes considering their abundance.

First calculate the percentage of each isotope.

Si(28) is 460 out of 500, percentage will be \frac{460}{500}\times 100=92%

Si-29 is 25 out of 500, percentage will be \frac{25}{500}\times 100=5%

Si-30 is 15 out of 500, percentage will be \frac{15}{500}\times 100=3%

Formula for average mass used will be:

Average mass=(% of Si-28×mass of Si-28)+(% of Si-29×mass of Si-29)+(% of Si-30×mass of Si-30)

=(0.92×27.98) amu+(0.05×28.98) amu+(0.03×29.97) amu

=(25.74+1.45+0.899) amu

=28.09 amu

Thus, average atomic mass of silicon is 28.09 amu.

liberstina [14]3 years ago
6 0

Answer;

=28.09 amu

Explanation;

In this problem, they did not give us the percentages. However, since we know the number of atoms, we can easily calculate the percentages. For example:  

(460 X 100)/500 = 92%  

If we do this for all three isotopes,

(460 × 25)/500 = 5 %

(460 × 15) /500 = 3%

-We get 92%, 5%, and 3%. (We'll assume these are absolute numbers for determining our significant figures).

Now the problem is just like the previous one. First convert the percentages into decimals. Then multiply those decimals by the masses and add. Here's the solution:  

= (0.92) X (27.98 amu) + (0.05) X (28.98 amu) + (0.03) X (29.97 amu)

= 25.74 amu  +  1.449 amu  + 0.8991 amu

= 28.09 amu

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<h3>Answer:</h3>

5.71 × 10² nm

<h3>Explanation:</h3>

The product of wavelength and frequency of a wave gives the speed of the wave.

Therefore;

Velocity of wave = Wavelength × Frequency

c = f ×λ

In our case;

Frequency = 5.25 × 10^14 Hz

Speed of light = 2.998 × 10^8m/s

But;

λ = c ÷ f

  = 2.998 × 10^8m/s ÷  5.25 × 10^14 Hz

  = 5.71 × 10^-7 m

But; 1 M = 10^9 nm

Therefore;

wavelength = 5.71 × 10^-7 × 10^9

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3 years ago
2) Nitrogen gas will react with hydrogen gas to produce ammonia, NH3, How many
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Answer:

12 grams of hydrogen gas

and 56 grams of nitrogen gas

The molar mass of ammonia is 17 g/mol.

68 grams of ammonia corresponds to  

17g/mol

68g

​

=4moles

4 moles of ammonia will be obtained from  

2

4×1

​

=2  moles of nitrogen and  

2

4×3

​

=6  moles of hydrogen.

The molar masses of nitrogen and hydrogen are 28 g/mol and 2 g/mol respectively.

2 moles of nitrogen corresponds to 2×28=56  grams.

6 moles of hydrogen corresponds to 6×2=12  grams.

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Describe the orbital diagram of an atom with eight electrons. Explain how this orbital diagram demonstrates Hund's rule. PLEASE
Mama L [17]

Answer:

The orbital notations shows the sequence of filling electrons into the orbitals of sublevels. This filling is based on some certain principles. For an atom with 16 electrons, the orbital diagram is shown below:  1s²2s²2p⁶3s²3p⁴ The maximum number of electrons in each sublevel of the orbitals are: 2 electrons for s-sublevel with one orbital

                 6 electrons for p-sublevel with three orbital

                 10 electrons for d-sublevel with five orbital

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According to the Aufbau's principle, sublevels with lower energy are filled before those with higher energy.

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Pauli's exclusion principle shows that no two electrons can have the same set of values for the four quantum numbers. Simply, no two electrons can spin in the same direction. Hund's rule states that electrons go into degenerate orbitals of sub-levles(s,p,d and f) singly before pairing commence. This rule shows that in each energy level, as the electron goes into the degenerate orbitals, they fill it one by one before they begin to pair up. As we know, each degenerate orbital can only accomodate 2 electrons. From the orbital diagram 1s²2s²2p⁶3s²3p⁴, the 3p sublevel has 3 orbitals. In each of the orbitals, two electrons would occupy them to give a maximum capacity of 6. But the sublevel has just 4 electrons. Based on Hund's rule, an electron will go into each of the 3 orbitals first. The remaining electron will now pair with the first degenerate orbital. This makes a total of 4 electrons.

Explanation:

8 0
3 years ago
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