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n200080 [17]
3 years ago
5

Which of the following is NOT an example of how watersheds can change over time?

Chemistry
1 answer:
kow [346]3 years ago
8 0

Answer:

D. Flooding occurs when too much rain falls upstream.

Explanation:

Flooding is not a change in a watershed.

A, B, and C are wrong. They all represent changes in a watershed.

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The electron in a hydrogen atom, originally in level n = 8, undergoes a transition to a lower level by emitting a photon of wave
timofeeve [1]

Explanation:

It is given that,

The electron in a hydrogen atom, originally in level n = 8, undergoes a transition to a lower level by emitting a photon of wavelength 3745 nm. It means that,

n_i=8

\lambda=3745\ nm

The amount of energy change during the transition is given by :

\Delta E=R_H[\dfrac{1}{n_f^2}-\dfrac{1}{n_i^2}]

And

\dfrac{hc}{\lambda}=R_H[\dfrac{1}{n_f^2}-\dfrac{1}{n_i^2}]

Plugging all the values we get :

\dfrac{6.63\times 10^{-34}\times 3\times 10^8}{3745\times 10^{-9}}=2.179\times 10^{-18}[\dfrac{1}{n_f^2}-\dfrac{1}{8^2}]\\\\\dfrac{5.31\times 10^{-20}}{2.179\times 10^{-18}}=[\dfrac{1}{n_f^2}-\dfrac{1}{8^2}]\\\\0.0243=[\dfrac{1}{n_f^2}-\dfrac{1}{64}]\\\\0.0243+\dfrac{1}{64}=\dfrac{1}{n_f^2}\\\\0.039925=\dfrac{1}{n_f^2}\\\\n_f^2=25\\\\n_f=5

So, the final level of the electron is 5.

4 0
3 years ago
Calculate the pka of hypochlorous acid. The ph of a 0.015 m solution of hypochlorous acid has a ph of 4.64.
o-na [289]

Answer:

  • pKa = 7.46

Explanation:

<u>1) Data:</u>

a) Hypochlorous acid = HClO

b) [HClO} = 0.015

c) pH = 4.64

d) pKa = ?

<u>2) Strategy:</u>

With the pH calculate [H₃O⁺], then use the equilibrium equation to calculate the equilibrium constant, Ka, and finally calculate pKa from the definition.

<u>3) Solution:</u>

a) pH

  • pH = - log [H₃O⁺]

  • 4.64 = - log [H₃O⁺]

  • [H_3O^+]= 10^{-4.64} = 2.29.10^{-5}

b) Equilibrium equation: HClO (aq) ⇄ ClO⁻ (aq) + H₃O⁺ (aq)

c) Equilibrium constant: Ka =  [ClO⁻] [H₃O⁺] / [HClO]

d) From the stoichiometry: [CLO⁻] = [H₃O⁺] = 2.29 × 10 ⁻⁵ M

e) By substitution: Ka = (2.29 × 10 ⁻⁵ M)² / 0.015M = 3.50 × 10⁻⁸ M

f) By definition: pKa = - log Ka = - log (3.50 × 10 ⁻⁸) = 7.46

5 0
4 years ago
PLS HELPPP How many moles of oxygen atoms (not molecules) are present in 6.41×1025 molecules of dinitrogen pentoxide (N2O5)? 1.
olga55 [171]

Answer:

(4) 266 moles

Explanation:

We have Dinitrogen Pentoxide N2O5

6.41*10^25 molecules are given

No of Moles of N2O5 = \frac{No of Molecules }{Avogadro's Number}

                                     = \frac{6.41 * 10^25}{6.022*10^23}

                                      = 106.5 mol

Now using Unitary Method

2 Mole of Nitrogen pentoxide require 5 mole of Oxygen to form N2O5

1 mole of N = \frac{5}{2}*O

In 106.5 mole of N  = \frac{5}{2}*106.5 = 266.25 mole

So, 6.41*10^25 molecules of N2O5 will require 266.25 mole of Oxygen atoms.

5 0
3 years ago
The chemical name for the compound formula NaCl is?
Mandarinka [93]

Answer:

The chemical name for the compound formula NaCl is sodium chloride.

7 0
4 years ago
Read 2 more answers
Complete the blank with the correct answer choice. 20 kilograms = _______ grams A. 20 B. 200 C. 2,000 D. 20,000
AVprozaik [17]

Answer:

20 kg = 20000 g

Option d

Explanation:

1 kg = 1000 g

20 kg . 1000 = 20000 g

3 0
3 years ago
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