Seawater vs. Blood Composition

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Questions and Answers

What is the approximate percentage of dissolved solids in seawater?

  • 3.5% (correct)
  • 35%
  • 0.35%
  • 96.5%

Which of these ions is significantly more abundant in blood than in seawater?

  • Hydrogen carbonate ($HCO_3^−$) (correct)
  • Sulfate ($SO_4^{2−}$)
  • Chloride ($Cl^−$)
  • Sodium ($Na^+$)

Why is extracting gold from seawater considered unfeasible?

  • The concentration of gold in seawater is extremely low. (correct)
  • The presence of other ions interferes with gold extraction.
  • The technology required for extraction is not yet developed.
  • Gold reacts with other elements in seawater, forming stable compounds.

In a solution of sugar and water, what determines which substance is the solvent?

<p>The substance present in greater quantity by mass or moles. (C)</p> Signup and view all the answers

Which of the following best describes a 'dilute' solution?

<p>A solution containing a small amount of solute. (D)</p> Signup and view all the answers

What term describes a solution that contains more solute than it can theoretically hold at a given temperature?

<p>Supersaturated (A)</p> Signup and view all the answers

According to the principle 'like dissolves like', which solvent is iodine ($I_2$) more likely to dissolve in?

<p>Carbon tetrachloride ($CCl_4$) (A)</p> Signup and view all the answers

What is the correct formula for calculating molarity (M)?

<p>$M = \frac{Moles\ of\ solute}{Liters\ of\ solution}$ (A)</p> Signup and view all the answers

If you have 0.500 L of solution containing 0.24 mol of NaOH, what is the molarity of the solution?

<p>0.48 M (C)</p> Signup and view all the answers

To prepare a solution of a specific molarity from a solid solute, what is the first step?

<p>Convert the mass of solute to moles. (D)</p> Signup and view all the answers

How is molality (m) defined?

<p>Moles of solute per kilogram of solvent. (C)</p> Signup and view all the answers

A metal piece contains 87.9 g of Fe in a 113 g sample. What is the mass percentage of Fe in the metal?

<p>77.8% (B)</p> Signup and view all the answers

What is the concentration of Pb in parts per thousand (ppth) if 0.6 g of Pb is present in 277 g of solution?

<p>2.17 ppth (C)</p> Signup and view all the answers

If a solution of $CaCl_2$ is labeled as 1 M, what is the concentration of $Cl^−(aq)$ in the solution?

<p>2 M (A)</p> Signup and view all the answers

Which process involves decreasing the concentration of a solute in a solution by adding more solvent?

<p>Dilution (D)</p> Signup and view all the answers

In the dilution equation ($M_1V_1 = M_2V_2$), what quantity remains constant before and after the change in concentration?

<p>Amount of solute (C)</p> Signup and view all the answers

A 2.19 M solution with an initial volume of 25.0 mL is diluted to 72.8 mL. What is the final concentration?

<p>0.750 M (C)</p> Signup and view all the answers

What is the primary use of concentration as a conversion factor in stoichiometry problems?

<p>To convert amount of solute to amount of solution or solvent. (A)</p> Signup and view all the answers

If you need to determine the mass of NaOH present in 0.765 L of 1.93 M NaOH, what additional information do you require?

<p>The molar mass of NaOH. (B)</p> Signup and view all the answers

What is the purpose of performing a titration experiment?

<p>To determine the amount of a substance in a sample. (B)</p> Signup and view all the answers

What are colligative properties dependent on?

<p>The number of solute particles in a solution. (B)</p> Signup and view all the answers

What is the range of possible values for mole fraction?

<p>0 to 1 (C)</p> Signup and view all the answers

A solution contains 12.0 g of $C_{10}H_8$ in 45.0 g of $C_6H_6$. What is the mole fraction of $C_{10}H_8$?

<p>0.179 (C)</p> Signup and view all the answers

What colligative property is described by Raoult's law?

<p>Vapor pressure depression (C)</p> Signup and view all the answers

How does the addition of a nonvolatile solute affect the boiling point of a solution?

<p>It increases the boiling point. (A)</p> Signup and view all the answers

Which of the following is the correct formula for calculating boiling point elevation?

<p>$\Delta T_b = K_b \times m$ (A)</p> Signup and view all the answers

What is the effect of solute particles on the freezing point of a solution?

<p>They decrease the freezing point. (D)</p> Signup and view all the answers

What is the definition of a semipermeable membrane?

<p>A membrane that allows certain small molecules to pass through but not others. (A)</p> Signup and view all the answers

What is the driving force behind osmosis?

<p>The tendency to equalize concentrations across a semipermeable membrane. (D)</p> Signup and view all the answers

Which of the following is the correct formula for calculating osmotic pressure?

<p>$\Pi = MRT$ (D)</p> Signup and view all the answers

Why should intravenous fluids have approximately the same osmotic pressure as blood serum?

<p>To prevent damage to red blood cells due to osmosis. (D)</p> Signup and view all the answers

Why is drinking seawater dangerous?

<p>It has a higher osmotic pressure than bodily fluids, causing cells to dehydrate. (D)</p> Signup and view all the answers

What is the van't Hoff factor ($i$)?

<p>The number of particles each solute formula unit breaks apart into when it dissolves. (D)</p> Signup and view all the answers

Which of these compounds would you expect to have the largest van't Hoff factor in an aqueous solution?

<p>Aluminum chloride ($AlCl_3$) (B)</p> Signup and view all the answers

In practice, why is the actual van't Hoff factor often less than the ideal van't Hoff factor?

<p>There are interactions between ions of opposite charge (A)</p> Signup and view all the answers

How does the inclusion of the van't Hoff factor modify the freezing point depression formula?

<p>$\Delta T_f = i \times K_f \times m$ (C)</p> Signup and view all the answers

Is the common culinary practice of adding a small amount of salt to water purportedly to raise its boiling point scientifically sound?

<p>No, the amount of salt typically used does not significantly raise the boiling point. (C)</p> Signup and view all the answers

Consider two separate aqueous solutions with equal molalities: one with NaCl and the other with $CaCl_2$. If all other factors are identical, which solution exhibits the lower vapor pressure and why? Assume complete disassociation.

<p>The $CaCl_2$ solution, because it has a larger van't Hoff factor ($i$). (D)</p> Signup and view all the answers

Imagine you're stranded on a (deserted fictional) island, with access to a lab containing tons of random chemicals. You're dehydrated and need drinking water. You have a large container of seawater. There are two processes you could use to obtain pure drinking water from it. Process 1: Boil the seawater and collect the condensed water. Process 2: Use reverse osmosis, applying high pressure to push water through a semipermeable membrane, separating it from the salt. Considering that all seawater and end-product water produced will eventually drain back into the island's water table (and eventually back into the ocean due to a crack in the island's rock bed), which would have the least impact on the long run drinkability on the the island, assuming both processes produce the same amount of drinking water?

<p>Process 1 via boiling would have the least impact to the long run viability, since thermal energy will eventually disipate into the local atmosphere, while the salt of process 2 remains (A)</p> Signup and view all the answers

Flashcards

Solvent

The major component of a solution.

Solute

The minor component of a solution.

Dilute

Describes a solution with very little solute.

Concentrated

Describes a solution with a lot of solute.

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Solubility

The maximum amount of solute that can dissolve in a solvent.

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Saturated solution

A solution containing the maximum amount of dissolved solute.

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Unsaturated solution

A solution containing less than the maximum amount of solute.

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Supersaturated solution

A solution containing more than the maximum amount of solute.

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"Like Dissolves Like"

Polar solutes dissolve in polar solvents, nonpolar in nonpolar.

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Molarity (M)

Moles of solute per liter of solution.

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Molality (m)

Moles of solute per kilogram of solvent.

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Mass Percentage

Mass of solute divided by the total mass, times 100%.

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Parts per Thousand (ppth)

Ratio of solute mass to total solution mass, times 1000.

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Parts per Million (ppm)

Ratio of solute mass to total solution mass, times 1,000,000.

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Parts per Billion (ppb)

Ratio of solute mass to total solution mass, times 1,000,000,000.

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Dilution

Adding solvent to decrease the concentration of solute.

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Concentration (of a Solution)

Removing solvent to increase the concentration of solute.

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Dilution Equation

M1V1 = M2V2

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Colligative properties

Properties dependent on the number of solute particles.

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Mole Fraction

Moles of a component divided by the total moles in a mixture.

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Vapor pressure

The pressure exerted by a gas in equilibrium with its liquid phase.

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Vapor Pressure Depression

Vapor pressure of a solution is lower than that of the pure solvent.

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Raoult's Law

P(solution) = X(solvent) * P°(solvent)

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Normal boiling point

The temperature at which a liquid's vapor pressure equals 1 atm.

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Boiling Point Elevation

Boiling point of a solution is higher than that of pure solvent.

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Change in Boiling Point (ΔTb)

The molality of the solution multiplied by a constant Kb.

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Freezing point

The temperature at which a liquid turns into a solid.

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Freezing Point Depression

Freezing point of a solution is lower than that of pure solvent.

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Change in Freezing Point (ΔTf)

ΔTf = m * Kf

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Semipermeable membrane

Membrane that allows some molecules to pass through, but not others.

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Osmosis

Net movement of solvent molecules through a semipermeable membrane.

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Osmotic pressure (Π)

Pressure difference across a semipermeable membrane.

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Osmotic Pressure Equation

Π = MRT

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van't Hoff factor (i)

Number of particles a solute formula unit breaks into upon dissolving.

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Freezing Point Depression (with i)

ΔTf = i * m * Kf

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Boiling Point Elevation (with i)

ΔTb = i * m * Kb

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Osmotic Pressure (with i)

Π = iMRT

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Study Notes

  • Seawater, essential for life on Earth, is primarily H2O with about 3.5% dissolved solids, mainly NaCl and other ions.
  • Bodily fluids, like blood, resemble seawater, with most ions more abundant in seawater than in blood.
  • Blood contains significantly more hydrogen carbonate ion (HCO3−) than seawater, playing a crucial role in controlling blood's acid-base properties.
  • Blood has a small amount of hydrogen phosphate ions (HPO42− and H2PO4−), which affect acid-base properties, while seawater has negligible amounts.
  • Blood has a negligible amount of the sulfate ion (SO42−), but this ion is present in seawater.
  • Gold exists in seawater in trace amounts (1 part per 1 × 10^13 parts of seawater), making extraction unfeasible, but totaling about 1.4 × 10^14 g in the world's oceans.
  • A solution is a homogeneous mixture behaving like a single substance, where the major component is the solvent and the minor component is the solute.
  • Solutions can exist in any phase, with the overall phase matching the solvent's phase.
  • Concentration describes the amount of solute in a solvent, with dilute indicating little solute and concentrated indicating a lot.
  • Solubility is the maximum amount of solute that can dissolve in 100 g of solvent at a given temperature.
  • A solution is saturated when it contains the maximum amount of solute, and unsaturated when it contains less.
  • Supersaturated solutions contain more solute than normally possible, achieved by heating and cooling carefully, but are unstable.
  • "Like dissolves like" predicts solute solubility based on intermolecular forces matching the solvent's. "Like dissolves like" is a general rule, not an absolute statement, for predicting whether a solute is soluble in a given solvent.
  • Molarity (M) is the number of moles of solute per liter of solution, expressed as M = moles of solute / liters of solution.
  • Molality (m) is the number of moles of solute per kilogram of solvent.
  • Mass percentage is calculated as (mass of component / total mass) × 100.
  • Parts per thousand (ppth) = (mass of solute / mass of solution) × 1000.
  • Parts per million (ppm) = (mass of solute / mass of solution) × 10^6.
  • Parts per billion (ppb) = (mass of solute / mass of solution) × 10^9.
  • For ionic solutions, ion concentration differs from salt concentration due to dissociation.
  • For example, 1 M CaCl2 yields 2 M Cl−(aq).
  • Total ion concentration is the sum of individual ion concentrations.
  • For example, 1 M NaCl has a total ion concentration of 2 M.
  • Dilution is adding solvent to decrease concentration, while concentration is removing solvent to increase concentration.
  • In both, the amount of solute remains constant.
  • The dilution equation is M1V1 = M2V2, where M is molarity and V is volume.
  • In concentrating solutions, the dilution equation is used because the amount of solute remains constant.
  • Molarity can be a conversion factor between the amount of solute and the amount of solution or solvent.
  • Concentrations can be used in stoichiometry problems, using the definition of the concentration unit as a conversion factor.
  • Concentrations can be used to relate quantities of one solution to quantities of another solution in balanced chemical equations.
  • Colligative properties of solutions depend on the number of solute particles, not their identity.
  • Mole fraction (χi) is the number of moles of a component divided by the total number of moles in the sample.
  • The sum of mole fractions of all substances in a mixture equals 1.
  • Vapor pressure depression is the lowering of a solution's vapor pressure compared to the pure solvent.
  • This is dependent on the fraction of solute particles.
  • Raoult's law: Psoln = χsolv * P°solv, where Psoln is the vapor pressure of the solution, χsolv is the mole fraction of the solvent particles, and P°solv is the vapor pressure of the pure solvent.
  • Boiling point elevation is the increase in a solution's boiling point compared to the pure solvent.
  • The change in boiling point (ΔTb) is calculated as ΔTb = m * Kb, where m is the molality of the solution and Kb is the boiling point elevation constant.
  • Freezing point depression is the decrease in a solution's freezing point compared to the pure solvent.
  • The change in freezing point (ΔTf) is calculated as ΔTf = m * Kf, where m is the molality of the solution and Kf is the freezing point depression constant.
  • Osmosis is the tendency for solvent molecules to move from a dilute solution to a concentrated solution through a semipermeable membrane.
  • Osmotic pressure (Π) is the pressure difference between two solutions separated by a semipermeable membrane.
  • The osmotic pressure of a solution is calculated as Π = M * R * T, where M is the molarity of the solution, R is the ideal gas law constant, and T is the absolute temperature.
  • Intravenous (IV) fluids need to have approximately the same osmotic pressure as blood serum to prevent cell damage.
  • For ionic solutes, the van't Hoff factor (i) is the number of particles each solute formula unit breaks apart into when it dissolves.
  • Revised equations to calculate the effect of ionization on colligative properties are: ΔTf = i * m * Kf, ΔTb = i * m * Kb, and Π = i * M * R * T.
  • For calculating vapor pressure depression in an ionic solution using Raoult's law, the mole fraction of solvent particles must be recalculated to account for the increased number of particles formed on ionization.

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