chem

 Solutions Test Review
KEY

Define homogenous, heterogenous, colloids, suspensions, miscible, immiscible, electrolyte, and non-electrolyte.
Homogenous – thoroughly, evenly mixed, solute & solvent are in the same phase
Heterogenous – not mixed evenly, solute & solvent are in different phases
Colloids – large particles which do not dissolve, but stay mixed
Suspensions – large particles which settle after stirring
Miscible – parts dissolve into each other & stay mixed
Immiscible – parts do not dissolve into each other, they may temporarily mix, but will separate (oil & water)
Electrolyte – a solute that will conduct electricity when dissolved
Non-electrolyte – a solute that will not conduct electricity when dissolved

Define dilute, concentrated, saturated, and supersaturated.
Dilute – not much solute dissolved
Concentrated – a lot of solute dissolved
Saturated – as much solute dissolved as possible for given temperature
Supersaturated – more solute dissolved than is normally possible

Explain how to make a saturated solution.
Keep adding solute and stirring until nothing more dissolves – now as much as can dissolve has dissolved.

Explain how to make a supersaturated solution.
Take a saturated solution and cool it. A cooler solvent cannot dissolve as much.
If all of the solute remains dissolved, it is supersaturated.
Otherwise, some of the solute will come out of solution – typically forming crystals.

Explain the relationship between bond types and solubility.
Solute and solvent must have the same bond type
Polar dissolves in polar, non-polar in non-polar. (Like dissolves like)

How does soap make it possible for water to dissolve oil?
Soap has a long non-polar part which attracts other non-polar, like oil.
Soap also includes an ion on the end, which attracts polar/ion materials, like water.

How do changes in temperature and pressure impact the solubility of a gas in a liquid? What is the name of the law involved with temperature and gas solubility?
Increasing temperature provides more energy, and the bonds between the gas and liquid break. This releases the gas from the solution. Therefore, increasing temperature decreases the solubility of a gas in liquid.
Increasing pressure “pushes” some of the gas molecules back into the solution. Therefore, increasing pressure increases solubility of a gas in liquid. This is Henry’s Law

Explain at the molecular level what is happening when a block of solute is dropped into a beaker of solvent and slowly dissolves.
Solvent molecules hit solute molecules and break the “bonds” holding the solute molecules to each other.
Then “bonds” are formed between the solute and solvent molecules

What is happening at the molecular level when a solution has excess solute in the bottom of the beaker, is saturated and is at equilibrium?
Some of the solute in the bottom of a beaker is dissolving. At the same time, some of the solute that is dissolved solidifies. Equilibrium means that these to processes happen at the same rate.

Name three factors that can increase the rate of solution of a solid in a liquid. Explain what is happening for each on the molecular level.
1)	Heat – adding heat energy provides energy to break the “bonds” holding the solute together, also provides more motion to the water molecules to increase collisions with the solute.
2)	Agitation (stirring) – when solute dissolves, it is held by water molecules directly surrounding the solute. This prevents additional water from reaching the solute to continue dissolving. Stirring moves the dissolved solute away and allows for more dissolving to happen.
3)	Increase surface area – all dissolving, like melting, happens at the surface. Increasing the surface increases the locations that dissolving is taking place.

Describe solutions, suspensions, and colloids, including relative particle sizes. How can each be identified?
Solution – small particles bond with the solvent, this completely dissolves the particles
Suspension – large particles that will settle out of the mixture what agitation stops.
Colloid – medium particles that stay suspended in the mixture, but do not dissolve. A colloid can be found by shining a light on it and seeing the light ray scatter in the mixture – Tyndall Effect.

Define solute and solvent.
The solute is the smaller part of the solution (by volume). It is dissolved by the solvent.

Why does the polarity of the two items determine if one will dissolve the other?
“Like dissolves Like” means that the polarity of the solute and solvent need to be the same.
Ionic compounds dissolve in polar water because the charges attract.
Non-polar, like oil, will dissolve in other non-polar, like gas.

Explain molarity, molality, normality, and parts per million (ppm).
Molarity – moles of solute per liter of solution
Normality – moles of H+ or OH- ions per liter of solution
Molality – moles of solute per kg of solvent
Parts Per Million (ppm) is how many parts of solute per million parts of solvent (3 ppm NaCl has 3 NaCl molecules per million water molecules)

How would you mix 1.17 L of 2 M NaCl?
(2 mol NaCl/1 L NaCl)(1.17 L)(58.44 g NaCl/1 mol NaCl) = 136.75 g NaCl
Mix 136.75 g NaCl with about ½ L water, dissolve, add water until you get 1.17 L of solution

How would you mix 3 m sugar using ½ kg of gasoline?
(3 mol sugar/1 kg gas)(.5 kg gas)(180.18 g sugar/1 mol sugar) = 270.27 g sugar
Mix 270.27 g sugar and ½ kg gas

What is the molarity and normality if 156 g of H3PO4 is dissolved in 454 ml of solution?
(156 g H3PO4)(1 mol H3PO4/98 g H3PO4) = 1.59 H3PO4
454 mL = .454 L
1.59 mol H3PO4/ .454 L = 3.50 M H3PO4
(3 H+/1 H3PO4 ) = 10.5 N H3PO4
Define electrolytes. What types of compounds are electrolytes? How is dissociation related?
Electrolytes are compounds that will conduct electricity when dissolved in water.
Ionic compounds will be electrolytes if they can dissolve.
The degree of dissociation (splitting into ions) determines if something is a strong electrolyte or a weak electrolyte

Define colligative properties. What two do we calculate?
Colligative properties are properties that depend on the molal concentration of particles in a solution.
We have been calculating the boiling point elevation and freezing point depression

What is happening at the molecular level that causes a solute to elevate the boiling point of a solvent?
The solute particles for attractions to the solvent. That means the solvent must gain enough energy to break free of other solvent (normal BP) and break free of the solute (more energy = higher BP)

Which compound will depress the freezing point of water the most - PbCl2, NaCl, or KCl? Why?
PbCl2 = 3 particles, NaCl = 2 particles, or KCl = 2 particles. PbCl2 will make the largest difference in BP and FP changes.

Which compound will elevate the boiling point of water the most - Ni(NO3)2, NH4ClO3, or (NH4)3PO4?
Ni(NO3)2 = 3 particles, NH4ClO3 = 2 particles, (NH4)3PO4= 4 particles, (NH4)3PO4 has the biggest impact on BP and FP

What will the new boiling point be if 121 g FeCl3 is dissolved in 1,201 mL water?
(+.51 °C/m)
121 g FeCl3 (1 mol FeCl3 /  162.2 g FeCl3)
.75 Mol FeCl3 /1.201 kg water = .62 m FeCl3
.62 m FeCl3 (4 mol particles/1 mol FeCl3)(+0.51 C/m) = +1.26 C
New BP = 101.26 C

What will the new freezing point be if 45 g NaCl is dissolved in 121 mL water?
(-1.86 °C/m)
45 g NaCl (1 mol NaCl/58.44 g NaCl
.77 mol NaCl/.121 kg water = 6.36 m NaCl
6.36 m NaCl (2 m particles/1 m NaCl)(-1.86 C/m) = -23.66 C

What is the heat of solution if a 300 ml sample of water goes from 21.0 C to 22.37 C when 74.55 g KCl is added to it.
74.55 g KCl (1 mol KCl/74.55 g KCl) = 1 mol KCl
(4.18J/1 g water 1 C)((300 g water)(1.37 C) = 1717.98 J = 1.71798 kJ
-1.71798 kJ/1 mol

What is the new concentration if 40 mL water is added to 30 mL of 2M HCl?
C1V1= C2V2.
(2M)(30mL) = (C2)(70 mL)
C2 = .86 M

How much 3 M NaOH is needed to react with 612 mL of 4 M H3PO4?
3NaOH  +  H3PO4->  Na3PO4  +  3H2O
(4 mol H3PO4/ 1 L H3PO4)(.612 L H3PO4)(3 mol NaOH/1 mol H3PO4 )(1 L NaOH/3 mol NaOH) = 2.49 L

Compare & contrast ionic and net ionic equations
Ionic shows all ions in reactants and products, net ionic only shows things that have changed
Write the ionic and net ionic equations for the following reactions:

1. FeSO4(aq) + BaCl2(aq) -> FeCl2(aq) + BaSO4(s)
Fe+2 + SO4-2(aq) + Ba+2 + 2Cl-(aq) -> Fe+2 + Cl- + BaSO4
Ba+2 + SO4-2 -> BaSO4

2. 2AgNO3(aq) + BaCl2(aq) -> 2AgCl(s) + Ba(NO3)2(aq)
2Ag+ + 2NO3- + Ba+2 + 2Cl- -> 2AgCl + Ba+2 + NO3-
2Ag+ + 2Cl- -> 2AgCl

3. FeSO4(aq) + 2NaCl(aq) -> FeCl2(aq) + Na2SO4(aq)
Fe+2 + SO4-2 + 2Na+ + 2Cl- -> Fe+2 + 2Cl- + 2Na+ + SO4-2
No Net Ionic Equation

Define spectator ion and identify the spectator ions for each of the three reactions listed above by circling them.
Spectator Ions are the ions that do not change during the reaction – they are the same charge on both sides of the equation.

Define dissociation and explain which types of compounds will dissociate.
Dissociation is an ionic compound splitting into the individual ions – only ionic compounds will dissociate

How can we tell it an ionic compound does not dissociate?
If an ionic compound will dissolve, it will dissociate at least a little.

How are strong and weak electrolytes associated with dissociation?
Electrolytes conduct electricity because they have ions. Things that dissociate well create a lot of ions and conduct electricity well. So strong electrolytes dissociate a lot.