36g of KOH dissolved in 800mL of water. What is the molality of the solution?

Chemistry

1 answer:

Zanzabum3 years ago

6 0

Answer:

0.80m of KOH

Explanation:

Molality is an unit of concentration defined as the ratio between moles of solute and kg of solvent.

In the problem, the solute is KOH and solvent is water.

Moles of 36g KOH -Molar mass: 56.1g/mol- are:

36g KOH × (1mol / 56.1g) = <em>0.642 moles of KOH</em>

Now, as density of water is 1g/mL, mass of 800mL of water is:

800mL × (1g / mL) × (1kg / 1000g) = <em>0.800kg of water</em>

Thus, molality is:

0.642moles of KOH / 0.800kg = <em>0.80m of KOH</em>

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Enter the net ionic equation representing solid chromium (iii) hydroxide reacting with nitrous acid. express your answer as a ba

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The net ionic equation of chromium (iii) hydroxide reacting with nitrous acid:

Cr(OH)₃ (s) + 3H⁺ (aq) ⇒ Cr³⁺ (aq) + 3H₂O (l)

<h3>Further explanation</h3>

The electrolyte in the solution produces ions.

The equation of a chemical reaction can be expressed in the equation of the ions

For strong electrolytes (the ionization rate = 1) is written in the form of separate ions, while the weak electrolyte (degree of ionization <1) is still written as an un-ionized molecule

In the ion equation, there is a spectator ion that is the ion which does not change (does not react) because it is present before and after the reaction

When these ions are removed, the ionic equation is called the net ionic equation

For gases and solids including water (H₂O) can be written as an ionized molecule

So only the dissolved compound is ionized ((expressed in symbol aq)

From the problem, it is stated that chromium (iii) hydroxide reacting with nitrous acid.

Reactions that occur:

Cr(OH)₃ (s) + 3HNO₂ (aq) ⇒ Cr(NO₂)₃ (aq) + 3H₂O (l)

Cr (OH)₃ solid form that does not decompose in the form of ions, as well as water (H₂O)

So the ionic equation becomes:

Cr(OH)₃ (s) + 3H⁺ (aq) + 3NO₂⁻ (aq) ⇒ Cr³⁺ (aq) + 3NO₂⁻ (aq) + 3H₂O (l)

There is an ion spectator that is 3NO₂⁻, so that if it is removed a net ionic equation will be formed:

Cr(OH)₃ (s) + 3H⁺ (aq) ⇒ Cr³⁺ (aq) + 3H₂O (l)

<h3>Learn more</h3>