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2 years ago

No copy on goógle:)..

Chemistry

2 answers:

Harlamova29_29 [7]2 years ago

7 0

Answer:

Heyyyyy...... vooooooo what a great question l love it

svetlana [45]2 years ago

6 0

Bach's music displays great emotions

Answer:

Explanation:

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Help with number 3 plz help due tomorrow!!!!!!!!!!

IceJOKER [234]

Answer:

which one?

Explanation:

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4 0

3 years ago

Read 2 more answers

Caffeine (C8H10N4O2) is a weak base with a pKb of 10.4. Calculate the pH of a solution containing a caffeine concentration of 41

RSB [31]

Answer:

pH → 7.47

Explanation:

Caffeine is a sort of amine, which is a weak base. Then, this pH should be higher than 7.

Caffeine + H₂O ⇄ Caffeine⁺ + OH⁻ Kb

1 mol of caffeine in water can give hydroxides and protonated caffeine.

We convert the concentration from mg/L to M

415 mg = 0.415 g

0.415 g / 194.19 g/mol = 2.14×10⁻³ mol

[Caffeine] = 2.14×10⁻³ M

Let's calculate pH. As we don't have Kb, we can obtain it from pKb.

- log Kb = pKb → 10^-pKb = Kb

10⁻¹⁰'⁴ = 3.98×10⁻¹¹

We go to equilibrium:

Caffeine + H₂O ⇄ Caffeine⁺ + OH⁻ Kb

Initially we have 2.14×10⁻³ moles of caffeine, so, after the equilibrium we may have (2.14×10⁻³ - x)

X will be the amount of protonated caffeine and OH⁻

Caffeine + H₂O ⇄ Caffeine⁺ + OH⁻ Kb

(2.14×10⁻³ - x) x x

We make the expression for Kb:

3.98×10⁻¹¹ = x² / (2.14×10⁻³ - x)

We can missed the -x in denominator, because Kb it's a very small value.

So: 3.98×10⁻¹¹ = x² / 2.14×10⁻³

√(3.98×10⁻¹¹ . 2.14×10⁻³) = x → 2.92×10⁻⁷

That's the [OH⁻]. - log [OH⁻] = pOH

- log 2.92×10⁻⁷ = 6.53 → pOH

14 - pOH = pH → 14 - 6.53 = 7.47

4 0

3 years ago

What is the mass of HF produced by three reaction of 3.0 10 to the 23 molecules of H2 with excess F2

JulijaS [17]

Answer:

It is 20. g HF

Explanation:

H2 + F2 ==> 2HF ... balanced equation

Since the question is asking us to find the mass of product formed, we will want to first convert the molecules of H2 into moles of H2 (we could do this at the end of the calculations, but it's just as easy to do it now).

moles of H2 present (using Avogadro's number):

3.0x1023 molecules H2 x 1 mole H2/6.02x1023 molecules = 0.498 moles H2

From the balanced equation, we see that 1 mole H2 produces 2 moles HF. Therefore, we can now find the theoretical mass of HF produced from 0.498 moles H2:

0.498 moles H2 x 2 moles HF/1 mol H2 = 0.996 moles HF formed.

The molar mass of HF = 20.01 g/mole, thus...

0.996 moles HF x 20.01 g/mole = 19.93 g HF = 20. g HF formed (to 2 significant figures)

6 0

3 years ago

How does a buffer resist change in ph upon addition of a strong acid?

lora16 [44]

Any buffer exists in this equilibrium

HA <=> $H^+ + A^-$
In a buffer, there is a large reservoir of both the undissociated acid (HA) and its conjugate base ( $A^-$ )

When a strong acid is added, it reacts with the large reservoir of the conjugate base ( $A^-$ ) forming a salt and water. Since this large reservoir of the conjugate base is used, the ph does not alter drastically, but instead resist the pH change.

8 0

3 years ago

Good day pleases help

klemol [59]

I can’t see the choices can you take another picture of this assignment please so i can help you

6 0

3 years ago

Read 2 more answers