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ankoles [38]
3 years ago
13

Help chem will mark brainlist

Chemistry
1 answer:
JulsSmile [24]3 years ago
7 0

Answer:

b

d

152.4

Explanation:

: )

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What is the pH at the equivalence point in the titration of a 25.7 mL sample of a 0.370 M aqueous nitrous acid solution with a 0
expeople1 [14]

Answer:

pH = 8.24

Explanation:

Nitrous acid (HNO₂) reacts with KOH, thus:

HNO₂ + KOH → KNO₂ + H₂O

Moles of HNO₂ are:

0.0257mL ₓ (0.370mol / L) = 0.00951moles.

In equivalence point, the complete moles of nitrous acid reacts with KOH producing potassium nitrite. There are needed:

0.00951mol ₓ (1L / 0.491mol) = 0.01937L ≡ 19.4mL of 0.491M KOH to reach equivalence point.

Total volume in equivalence point is: 19.4mL + 25.7mL = <em>45.1mL</em>

Potassium nitrite is in equilibrium with water, thus:

NO₂⁻ + H₂O ⇄ HNO₂ + OH⁻

Where equilibrium constant, Kb, is defined as:

Kb = 1.41x10⁻¹¹ = \frac{[OH^-][HNO_2]}{[NO_2]}

In equilibrium, molarity of each compound are:

[NO₂⁻]: 0.00951mol/0.00451L - X = 0.211M - X

[HNO₂]: X

[OH⁻]: X

<em>Where X is reaction coordinate</em>

Replacing in Kb:

1.41x10⁻¹¹ = \frac{[X][X]}{[0.211 -X]}

0 = X² + 1.41x10⁻¹¹X - 2.97x10⁻¹²

Solving for X:

X = -1.72x10⁻⁶ <em>FALSE ANSWER. There is no negative concentrations.</em>

X = 1.72x10⁻⁶. <em>Right answer.</em>

That means:

[OH⁻]: 1.72x10⁻⁶M

As pOH is -log [OH⁻] and pH = 14-pOH:

pOH = 5.76; <em>pH = 8.24</em>

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3 years ago
Какая система называется моделью химия
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The molar heat of fusion of platinum (Pt) is 4.700 kcal/mol. How much heat must be added to 85.5 g of solid platinum at its melt
Andre45 [30]
The heat required to completely melt the given substance, platinum, we just have to convert first the given mass in mole and multiply the answer to its molar heat of fusion.. 
                              Hf  = mass x (1/molar mass) x molar heat of fusion
                            Hf = (85.5 g) x (1 mole/195.08 g) x 4.70 kcal/mol
                                   Hf = 2.06 kcal
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2. Explain why sedimentary rock layers of the North and South Rim(side) of the Grand Canyon are the same age, using Steno’s Prin
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Answer:

Law of Lateral Continuity The Grand Canyon.

and

he same rock layers on opposite sides of the canyon. The matching rock layers were deposited at the same time, so they are the same age.

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What is the mechanism by which Ozone is formed in the presence of sunshine?
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not sure if this is what you want but hope it helps!!!
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