Air, Water and Solubility

Match each chemical compound or process related to water hardness with its correct description or function.

Match each atmospheric pollutant or component in Column I with its corresponding chemical mode of action or environmental transformation mechanism in Column II.

A $200\text{ cm}^3$ sample of a saturated potassium trioxonitrate(V) solution, $\text{KNO}_3$, at $60^\circ\text{C}$ has a concentration of $1.5\text{ mol/dm}^3$. The solution is cooled to $25^\circ\text{C}$ to form a supersaturated solution. When a seed crystal is added, excess solute crystallizes until a new saturated concentration of $0.5\text{ mol/dm}^3$ is reached at $25^\circ\text{C}$. What mass of $\text{KNO}_3$ crystallizes out of the solution? [Molar mass of $\text{KNO}_3 = 101\text{ g/mol}$]

If the solubility of sodium hydroxide ($\text{NaOH}$) in water at $25^\circ\text{C}$ is $0.50\text{ mol/dm}^3$, what is its concentration in $\text{g/dm}^3$? $[\text{Na} = 23, \text{O} = 16, \text{H} = 1]$

A $13.90\text{ g}$ sample of hydrated iron(II) tetraoxosulfate(VI), $\text{FeSO}_4 \cdot x\text{H}_2\text{O}$, was heated strongly until all water of crystallization was driven off. The mass of the remaining anhydrous salt was $7.60\text{ g}$. What is the value of $x$? $[\text{Fe} = 56, \text{S} = 32, \text{O} = 16, \text{H} = 1]$

A $100\text{ cm}^3$ sample of dry air is passed slowly over excess heated copper turnings in a combustion tube until no further contraction in volume occurs. Assuming oxygen accounts for $21\%$ of air by volume, what is the volume of the remaining unreacted gas in $\text{cm}^3$ at room temperature and pressure?

A $400\text{ cm}^3$ sample of polluted air containing nitrogen dioxide ($\text{NO}_2$), carbon dioxide ($\text{CO}_2$), and unpolluted air components is passed sequentially through two absorption reagents. First, passing the sample through concentrated sodium hydroxide ($\text{NaOH}$) solution absorbs both acidic pollutants ($\text{NO}_2$ and $\text{CO}_2$), reducing the volume of the gas by $40\text{ cm}^3$. The remaining gas mixture is then passed through alkaline pyrogallol, where oxygen ($\text{O}_2$) is completely absorbed, causing a further volume reduction of $75.6\text{ cm}^3$. Assuming oxygen constitutes $21\%$ by volume of the unpolluted portion of the air sample, what is the percentage by volume of nitrogen dioxide ($\text{NO}_2$) in the original polluted air sample?

A saturated solution of potassium chloride ($\text{KCl}$) contains $14.9\text{ g}$ of the salt dissolved in $100\text{ g}$ of water at $25^\circ\text{C}$. What is the solubility of potassium chloride in $\text{mol/dm}^3$ at this temperature?

(Take density of water = $1.0\text{ g/cm}^3$, relative atomic masses: $\text{K} = 39$, $\text{Cl} = 35.5$)

Match each atmospheric pollutant listed on the left with its primary health or environmental impact listed on the right.

A $5.00\text{ g}$ sample of hydrated copper(II) tetraoxosulfate(VI), $\text{CuSO}_4 \cdot x\text{H}_2\text{O}$, was heated strongly in a crucible until all water of crystallization was driven off, leaving an anhydrous residue of mass $3.20\text{ g}$. What is the value of $x$ in the formula of the hydrated salt? $[\text{Cu} = 64, \text{S} = 32, \text{O} = 16, \text{H} = 1]$

A sample of well water forms a white precipitate when boiled and requires a large amount of soap to produce lather. Which soluble compound present in the water is responsible for this temporary hardness?

Arrange the following steps in the correct chronological order to illustrate how water hardness is removed using the zeolite (permutit) ion-exchange method and how the column is subsequently regenerated.

During the municipal purification and treatment of river water for public supply, several chemical reagents are added at different stages of the process. Which of the following chemicals is correctly paired with its primary functional role in this water treatment scheme?

Three liquid mixtures, $X$, $Y$, and $Z$, were subjected to laboratory tests to determine their physical properties:

- Mixture $X$ scatters a focused beam of light (Tyndall effect), leaves no residue on ordinary filter paper, but fails to pass through a semi-permeable membrane.
- Mixture $Y$ does not scatter light, leaves no residue on ordinary filter paper, and passes freely through a semi-permeable membrane.
- Mixture $Z$ leaves a visible residue on ordinary filter paper and separates into two distinct layers after standing undisturbed.

Which of the following correctly identifies mixtures $X$, $Y$, and $Z$ respectively?

Match each mixture listed on the left with its correct classification or colloidal type on the right based on particle size and physical characteristics.

A $500\text{ cm}^3$ sample of air collected near an industrial plant containing nitrogen ($\text{N}_2$), oxygen ($\text{O}_2$), carbon dioxide ($\text{CO}_2$), and sulfur dioxide ($\text{SO}_2$) pollutant was passed through concentrated potassium hydroxide ($\text{KOH}$) solution, reducing the gas volume to $485\text{ cm}^3$. The residual gas mixture was subsequently passed through excess alkaline solution of pyrogallol, resulting in a final volume of $383\text{ cm}^3$. What is the percentage by volume of oxygen in the original air sample?

Match each chemical solute with its characteristic solubility curve behavior in water as temperature increases.

The solubility of a solute $X$ in water is $1.5\text{ mol/dm}^3$ at $80^\circ\text{C}$ and $0.5\text{ mol/dm}^3$ at $30^\circ\text{C}$. If $250\text{ cm}^3$ of a saturated solution of $X$ at $80^\circ\text{C}$ is cooled to $30^\circ\text{C}$, what mass of $X$ will crystallize out of the solution? [Molar mass of $X = 160\text{ g/mol}$]

An aqueous mixture passes completely through standard filter paper without leaving any residue, but its particles are retained when passed through a parchment (semi-permeable) membrane. When illuminated by a narrow light beam in a dark room, the mixture scatters light, and under an ultramicroscope, its particles exhibit continuous zig-zag movement without settling under gravity. Which of the following correctly classifies this mixture and describes the characteristic behavior of its dispersed phase?

The solubility of copper(II) tetraoxosulfate(VI), $\text{CuSO}_4$, at $60^\circ\text{C}$ and $20^\circ\text{C}$ is $40.0\text{ g}$ and $21.0\text{ g}$ per $100\text{ g}$ of water respectively. Calculate the mass of $\text{CuSO}_4$ in grams that will crystallize out of solution when a saturated solution containing $250\text{ g}$ of water is cooled from $60^\circ\text{C}$ to $20^\circ\text{C}$.