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3 years ago

Why do electrons enter the 4s orbital before entering the 3d orbital?

Chemistry

1 answer:

Alla [95]3 years ago

3 0

because the 4s orbitals have a lower energy than the 3d, and so the 4s orbitals are filled first.

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Two gases X and Y are found in the atmosphere in only trace amounts because they decompose quickly. When exposed to ultraviolet

igomit [66]

Answer:

1. Yes

2. After 68.1 mins, pX < pY.

Explanation:

Assuming the total gas pressure is 1 atm, let the partial pressure of Y be y, partial pressure of X will be 0.25y + y = 1.25y

1.25y + y = 1atm

2.25y = 1 atm

y = 1 atm / 2.25 = 0.44 atm

Then partial pressure of X = 0.56 atm

The partial pressure of a gas in a mixture of gases is directly proportional to the mole fraction of the gas.

Therefore the mole fraction of X and Y is 0.56 and 0.44 respectively.

The partial pressures of X and Y becomes half of their original values at 1.25 h = 85 min and Y at 150 min respectively.

The partial pressure after some time can be calculated from the half-life equation :

m = m⁰ * 1/2ⁿ

Where m = the remaining mass, m⁰ = initial mass, and n is number of half-lives undergone.

Let partial pressures represent the mass, and n for X and Y be a and b respectively:

pX = 0.56/2ᵃ

pY = 0.44/2ᵇ

We then determine when Partial pressure of X, pX = Partial pressure of Y, pY

0.56/2ᵃ = 0.44/2ᵇ

2ᵃ/2ᵇ = 0.56/0.44

2ᵃ/2ᵇ = 1.27

2ᵃ⁻ᵇ = 2⁰°³⁴⁵

a - b = 0.345

Let this time be t, therefore,

For X; t = 85a and For Y: t = 150b

85a = 150b

then, a = 1.76b

1.76b - b = 0.345

0.760b = 0.345

b = 0.454 and,

a = 0.345 + 0.454 = 0.799

So, X goes through 0.779 half-lives while Y goes through 0.454 half-lives Then, the time for both X and Y to have the same amount is:

t = 150 * 0.454 = 68.1 min

After 68.1 mins, pX < pY.

5 0

3 years ago

An isotope of yttrium has 39 protons and 59 neutrons. what is the atomic mass of that isotope?

Charra [1.4K]

We can define atomic mass the total of number of protons and number of neutrons in an atom or isotope.
So when an isotope of yttrium has 39 protons and 59 neutrons, its atomic mass is equal to;
number of protons + number of neutrons = 39 + 59 = 98

8 0

3 years ago

The Tisza-Danube cyanide spill is an example of all of the following except a general pollution. b accidental pollution. c point

Serjik [45]

Answer: Its B!

Explanation:

4 0

3 years ago

Calculate the mass of nitric acid required to make a 250mL solution with 2.40 ph

meriva

The mass of nitric acid required to make the given solution is 0.0627 g.

The given parameters:

Volume of the acid, V = 250 mL
pH of the acid, = 2.4

The hydrogen ion (H⁺) concentration of the nitric acid is calculated as follows;

$H^+ = 10^{-pH}\\\\H^+ = 10^{-2.4}\\\\H^+ = 0.00398$

The molarity of the nitric acid is calculated as follows;

$= 0.00398 \ H^+ \times \frac{1 \ M \ HNO_3}{1 \ H^+} \\\\= 0.00398 \ M$

The number of moles of the nitric acid is calculated as follows;

$moles = M\times L\\\\moles = 0.00398\ M \ \times \ \frac{250 \ mL}{1000} \\\\moles = 9.95 \times 10^{-4} \ mol.$

The molar mass of nitric acid is calculated as;

$HNO_3 = (1) \ + (14) \ + (16 \times 3) = 63 \ g/mol$

The mass of the nitric acid contained in the calculated number of moles is calculated as;

$mass = moles\ \times \ molar \ mass\\\\mass = 9.95\times 10^{-4} \ mol. \ \times \ 63 \ g/mol\\\\mass = 0.0627 \ g$

Thus, the mass of nitric acid required to make the given solution is 0.0627 g.

Learn more about molarity of acids here: brainly.com/question/13864682

3 0

2 years ago

Large-scale environmental catastrophes _______.

Ymorist [56]

Answer:

D. All of the Above

Explanation:

i just took the test on edgenuity

3 0

3 years ago