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Alex_Xolod [135]
3 years ago
10

A guy swam a 50 meter freestyle in 21.93 seconds. How fast is this in miles per hour?

Chemistry
1 answer:
lara [203]3 years ago
5 0

Answer:

<h2>Speed = 5.107 mile/hr</h2>

Explanation:

<h3>Given:</h3>

<u>distance</u> =50m = 0.0311 mile

<u>Time</u>= 21.93 seconds/3600 =0.00609 hour

<u>Speed</u><u>=</u>?

<h3>Speed= Distance / Time </h3><h3> = 0.0311 / 0.00609</h3><h3> = 5.107 mile/hr</h3>

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If the K a Ka of a monoprotic weak acid is 7.3 × 10 − 6 , 7.3×10−6, what is the pH pH of a 0.40 M 0.40 M solution of this acid?
olga_2 [115]

Answer:

pH =3.8

Explanation:

Lets call the monoprotic weak acid HA, the dissociation equilibria in water will be:

HA + H₂O   ⇄ H₃O⁺ + A⁻    with  Ka = [ H₃O⁺] x [A⁻]/ [HA]

The pH is the negative log of the H₃O⁺ concentration, we know the equilibrium constant, Ka and the original acid concentration. So we will need to find the [H₃O⁺] to solve this question.

In order to do that lets set up the ICE table helper which accounts for the species at equilibrium:

                          HA                                   H₃O⁺                          A⁻          

Initial, M             0.40                                   0                              0

Change , M          -x                                     +x                            +x

Equilibrium, M    0.40 - x                              x                               x

Lets express these concentrations in terms of the equilibrium constant:

Ka = x² / (0.40 - x )

Now the equilibrium constant is so small ( very little dissociation of HA ) that is safe to approximate 0.40 - x to 0.40,

7.3 x 10⁻⁶ = x² / 0.40  ⇒ x = √( 7.3 x 10⁻⁶ x 0.40 ) = 1.71 x 10⁻³

[H₃O⁺] = 1.71 x 10⁻³

Indeed 1.71 x 10⁻³ is small compared to 0.40 (0.4 %). To be a good approximation our value should be less or equal to 5 %.

pH = - log ( 1.71 x 10⁻³ ) = 3.8

Note: when the aprroximation is greater than 5 % we will need to solve the resulting quadratic equation.

4 0
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What does the principal quantum number determine? Check all that apply. Check all that apply. the possible number of electorns o
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Answer:

ii) the energy of the electron on the outer shell

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