PLEASE HELP WITH CHEMISTRY !! BRAINLIEST AND 10 POINTS !!

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 = 45.1mL

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

Where X is reaction coordinate

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 FALSE ANSWER. There is no negative concentrations.

X = 1.72x10⁻⁶. Right answer.

That means:

[OH⁻]: 1.72x10⁻⁶M

As pOH is -log [OH⁻] and pH = 14-pOH:

pOH = 5.76; pH = 8.24

3 0

3 years ago

What happens to the mass of substances during a physical change?

Anna [14]

Here are the answers in order:

1. During a physical change the substance changes physically.

2. The law of conservation of mass is a law stating the conservation of mass cannot be higher than 46mg or lower than 32mg.

3. A hypothesis is a guess that you make before completing a science experiment, it can be considered a law because it is important to know why you are making the guess.

4. During a chemical change the mass is changing colors. This is a representation of a chemical change.

5. Oil is a non-renewable resource, so it cannot demonstrate the conservation of mass.

6. When the color of the substance has changed or when it explodes.

7. Reactants are the objects that react when in a chemical change.

8. If you follow the rule of not going higher than 46mg and not lower than 32mg then it will automatically follow this law.

Chemical Reactions Part One Video:

1. mass

2. erupt-ant

3. reactant

4. object

5. mixtures

6. molecules

7. color changed

Questions again:

1. A chemical reaction

2. A physical change

3. Because if it is no higher than 46mg and no lower than 32mg then it will follow on it's own.

8 0

3 years ago

Read 2 more answers

How does the number of subatomic particles change as the carbon isotope decays?

Rzqust [24]

Answer:

Explanation:

C decays by a process called beta decay. During this process, an atom of 14C decays into an atom of 14N, during which one of the neutrons in the carbon atom becomes a proton. This increases the number of protons in the atom by one, creating a nitrogen atom rather than a carbon atom.

5 0

2 years ago

Is aluminum foil an element, compound or mixture

lora16 [44]

It is an element. Aluminun foil is aluminum prepared in thin leaves.

3 0

3 years ago

Read 2 more answers

A tank contains hermit crabs and frogs. What kinds of animals are inside of the tank? Check all that are true. fish invertebrate

aev [14]

Answer:

Vertebrates, invertebrates, and amphibians.

Explanation:

Vertebrates have backbones. Frogs have back bones.

Invertebrates do not have backbones. Hermit crabs do not have back bones.

Amphibians are cold-blooded vertebrate animals. Frogs are cold-blooded vertebrate animals.

5 0

3 years ago