Assignment 3: 12.1 - 12.5

Select the steps that are associated with energy entering the system. Check all that apply.

*the separation of solvent molecules *the separation of solute molecules the mixing of solute and solvent molecules

A student working on a laboratory experiment dissolves a hypothetical solute AB in water. The student observes that the flask becomes cold to the touch. Use the diagram to determine which of the following equations accurately shows the relationship between the magnitude of the enthalpy values for each step in the dissolution of AB in water for a flask that becomes cold to the touch.

*|ΔH1+ΔH2|>|ΔH3| |ΔH1+ΔH2|=|ΔH3| |ΔH1+ΔH2|<|ΔH3|

If the solution described in the introduction is cooled to 0 ∘C what mass of K2SO4 will crystallize? Enter your answer numerically in grams.

0 g

At 1 atm, how many moles of CO2 are released by raising the temperature of 1 liter of water from 20∘C to 25∘C? Express your answer to four decimal places and include the appropriate units.

0.0030 mol

What is the Henry's law constant for CO2 at 20∘C? Express your answer to three significant figures and include the appropriate units.

0.0380 mol/L⋅atm

What is the molarity of a 11.2 % by mass glucose (C6H12O6) solution? (The density of the solution is 1.03 g/mL .) Express your answer with the appropriate units.

0.640 M

percent by mass

13.6% by mass

A 500.0 ml sample of pure water is allowed to come to equilibrium with pure oxygen gas at a pressure of 755 mmHg. What mass of oxygen gas dissolves in the water? (The Henry's law constant for oxygen gas is 1.3×10−3M/atm.)

15.7 g 23.0 g *0.021 g 0.030 g

Crystallization is the opposite of dissolution. Since solids tend to dissolve better at higher temperatures, we can cause them to crystallize (i.e., undissolve) from a solution by lowering the temperature. If the solution described in the introduction is cooled to 0 ∘C, what mass of KNO3 should crystallize? Enter your answer numerically in grams.

16 g

What pressure is required to achieve a CO2 concentration of 7.70×10−2 M at 20∘C? Express your answer to three significant figures and include the appropriate units.

2.03 atm

mole percent

8.15 mole percent

The following substances dissolve when added to water. Classify the substances according to the strongest solute-solvent interaction that will occur between the given substances and water during dissolution. Drag the appropriate items to their respective bins. Not all bins may contain an item and some bins may contain multiple items.

Ion-Ion forces: Dipole-dipole forces: HF, CH3OH Ion-Dipole forces: CaCl2, CuSO4 London dispersion forces:

For which salt, K2SO4, Li2SO4, KClO4, or NH4Cl, will increasing the temperature of the water have the greatest change in solubility per 100 g solvent?

Li2SO4 *NH4Cl KClO4 K2SO4

molarity

M = 4.18 M

Rank the following substances in order from most soluble in water to least soluble in water: ethane, C2H6; 2-pentanol, C5H11OH; table salt, NaCl; and propane, C3H8. Rank from most to least soluble in water. To rank items as equivalent, overlap them.

Most soluble to least: table salt, 2-pentanol, propane, ethane

Which compound do you expect to be miscible with octane (C8H18)?

NH3 *CBr4 CH3OH H2O

Identify the type of interactions involved in each of the following processes taking place during the dissolution of sodium chloride (NaCl) in water. Drag the appropriate items to their respective bins.

Solvent-Solvent interactions: interactions involving dipole-dipole interaction, interactions between the water molecules Solute-Solute interactions: interactions between ions of sodium chloride, interactions involving ion-ion attractions Solute-Solvent interactions: interactions formed between the sodium ions and the oxygen atoms of water molecules, interactions formed between the chloride ions and the hydrogen atoms of water molecules

Predict what must happen when a beaker containing a solution of lithium chloride is heated. Check all that apply.

The ΔHsoln value will decrease. The ΔH3 value will increase. The reaction will become endothermic. *Energy will be transferred into the system.

A solid mixture consists of 35.7 g of KNO3 (potassium nitrate) and 6.3 g of K2SO4 (potassium sulfate). The mixture is added to 130. g of water. Use this solubility curve (Figure 1) to answer the questions. Consider the mixture described in the introduction. At 60 ∘C, to what extent will each solute be dissolved? Drag each item to the appropriate bin.

Totally dissolved: KNO3, K2SO4 Partially dissolved: Not dissolved:

To what volume should you dilute 40.5 mL of a 5.55 M KI solution so that 23.5 mL of the diluted solution contains 3.50 g of KI?

V = 251 mL

mole fraction

X = 8.15×10−2

molality

m= 4.93m

A 2.200×10−2 M solution of NaCl in water is at 20.0∘C. The sample was created by dissolving a sample of NaCl in water and then bringing the volume up to 1.000 L. It was determined that the volume of water needed to do this was 999.4 mL . The density of water at 20.0∘C is 0.9982 g/mL. Calculate the molality of the salt solution. Express your answer to four significant figures and include the appropriate units.

mNaCl = 2.205×10−2 m

Five different substances are given to you to be dissolved in water. Which substances are most likely to undergo dissolution in water?

octane, C8H18 heptane, C7H16 *sodium iodide, NaI *potassium fluoride, KF *lithium bromide, LiBr

Calculate the concentration of the salt solution in parts per million. Express your answer as an integer to four significant figures and include the appropriate units.

parts per million NaCl = 1287 ppm

Calculate the concentration of the salt solution in percent by mass. Express your answer to four significant figures and include the appropriate units.

percent by mass NaCl = 0.1287 {\rm \\%}

The chemical equation for the dissolution of lithium chloride (LiCl) is LiCl(s) ⟶H2O Li+(aq)+Cl−(aq) The ΔHsoln value for this process is −37.4 kJ/mol. Select the ΔH values associated with the dissolution of lithium chloride that are exothermic. Check all that apply.

ΔH1: energy associated with the separation of water molecules ΔH2: energy associated with the separation of LiCl ions *ΔH3: energy associated with the formation of water-ion interactions *ΔHsoln: the enthalpy of solution

Silver nitrate has a lattice energy of −820.kJ/mol and a heat of solution of +22.6kJ/mol. Calculate the heat of hydration for silver nitrate.

ΔHhydration = -797 kJ/mol

Calculate the mole fraction of salt in this solution. Express the mole fraction to four significant figures.

χNaCl = 3.970×10−4