Exam 1 Review Flashcards
According to Henry’s Law, if the pressure increases to 2 atm and equilibrium is restored, which represents the equilibrium at 2 atm.
- The one where there are less gas molecules where there is 2 atm of pressure.
- the more pressure the gas has the more it will dissolve in the liquid.
KI does not dissolve well in nonpolar solvents because…
- solute-solute interactions are much larger than solvent-solvent or solute-solvent.
What are the major solute-solvent interactions created when HOCH2CH2OH dissolves in water?
- hydrogen bonding because a solute is bonding to water, which creates hydrogen bonding.
What is expected to have the highest surface tension @ 25C?
- Which ever has the most OH- groups, the more OH- groups the higher its surface tension.
BP os a liquid is 64C and the enthalpy change of this liquid to gas is 32.21 kJ/mol. What is the entropy, Svap?
- dS= dH/T
32.21/337.15 x 1000 = 95.5 J/mol * K
Which has the highest viscosity?
- Which ever has the most OH- groups, the OH- groups the more viscous.
What is the weight percent of vitamin C, in a solution made by dissolving 1.30 g of vitamin C, C6H8O6, in 55g of water?
- weight percent= mass of solute/total mas of solution x 100
1.3/(55+1.3) x 100 = 2.31%
According to the diagram, the solid phase of this substance…
- is more dense than the liquid phase.
The temperature and pressure at which all 3 phases can coexist in equilibrium…
- is wherever the 3 lines touch, because that is their equilibrium state.
.45atm & 130C
How much heat is required to convert 3.12 moles of liquid benzene at 75.1C to gaseous benzene at 115.1C?
- Q= (n x Cm x dT) + (n x dH) + (n x Cm x dT)
- heat total = (heat required to get to boiling point) + (heat required to vaporize) + (heat required to get to gas)
- don’t forget to convert J to kJ
2.164 + 95.84 + 3.99 = 101.994 kJ
What is the freezing point of a solution of 2.86 MgCl2 in 100 g of water? Kf for water is 1.86
- Tf = i x Kf x m
- i= van’t hoff factor
- m= molality (moles of MgCl2/mass of water in Kg) = .3
- 0 - 1.67, because is freezing
3 x 1.86 x .3 = 1.67, 0 - 1.67= -1.67
How many cations M are in the unit cell?
- 1 because there is one on each corner and takes up 1/8 each
What is the empirical formula of the mineral?
- M(8) x 1/8 (on the corners), M’(1) x 1 (it is in the center), A(6) x 1/2 (they are on the faces).
MM’A3
What is the mole fraction of ethanol in a solution made by dissolving 7.3 g of ethanol, C2H5OH, in 53.6 grams of water?
- mole fraction formula: X= number of moles of ethanol/ (number of moles of ethanol + number of moles of water)
- Find the number of moles of each thing before plugging into formula
Manganese crystallizes in a body centered cubic structure. What is the coordination number?
unit cells coord. # atom #
* simple unit cell 6 1
* body centered cubic 8 2
* face centered cubic 12 4
* cubic closest packed 12 4
8
How many atoms are in one bosy-centered cubic unit cell of a metal?
2
Germanium crystallizes in a face centered cubic unit cell and has an edge length of 452 pm. What is its density?
- face centered cubic unit cell has 4 atoms total (corners+face)
- mass of 1 unit cell = 4 x mass of Germanuim atom / Avogadros number
- volume of 1 unit cell = (edge length)^3 (and convert to cm (10^10)
- density = mass/volume
5.22 g/cm^3
When 2.36g of a nonvolatile solute is dissolved in 100g of solvent, the largest change in freezing point will be achieved when the solvent is…
- dTf= Kf x m
- the greater the Kf value the more will be the decrease in freezing point
tert-butanol, Kf = 9.1
An element forms a body-centered cubic crystalline substance. The edge of the cubic unit cell is 287pm, and the density of the crystal is 7.92 g/cm^3. Calculate the atomic weight of the substance.
- body centered cubic crystal has 2 atoms (center + corners
- volume = a^3, and convert pm to cm
- mass of unit cell = density x volume
- multiply by avogadros and divide my number of atoms
56.4 g
What volume of a .716M KBr solution is needed to provide 10.5g of KBr?
- number of moles of KBr= weight of KBr/molar mass of KBr
- molarity = moles/ vol. in L
- Vol. in L = moles/Molarity
.08823 mol/.716 M = .123L = 123 mL
When a liquid is heated at its boiling point, the…
- temperature of the liquid remains the same as long as any liquid is present
Identify the packing shown in the figure below…
simple cubic
Which of the following forms an ionic solid?
- metal + nonmetal = ionic solid
CsNO3
Which of the following phase changes has a positive value for its entropy change?
- liquid to gas = dS increases
- solid to gas = dS increases
- solid to liquid = dS increases
creating steam
KI crystallizes in a cubic unit cell with I- ions on each corvers and face. How many K+ and I- ions are in each unit cell of KI?
3 face and 1 on corner each = 4
4K+ ions and 4I- ions
