Unit 1+2
How many moles are in 88 grams of Carbon Dioxide (CO2)
2 moles
~Moles of CO2 = actual mass/molar mass
What are the only intermolecular forces present in non-polar molecules?
London dispersion forces
~Since there is no H,O, or N present to create hydrogen bond and it isn't polar so there can't be dipole-dipole bonds.
In an endothermic reaction, energy is?
added to break bonds
~more energy is absorbed when the bonds in the reactants are broken than is released when new bonds are reformed in the products.
if Q > Keq, the reaction
favors the forward direction
~because if Q is less than K, the denominator of Q is larger. Since the denominator is the reactants, this means that there are more reactants than there should be at equilibrium.
What is weak acid/strong base equivalence pH?
pH=7
pH>7
pH<7
pH>7
~This is because the solution is composed of water, the cation of a strong base (neutral), and the anion of a weak acid (a base)
Which of the following is the electron configuration for the valence electrons of Sn in the ground state?
5s^2,5p^2
~Sn is in the fifth row of the periodic table, which represents the outermost shell N=5, Sn also has four valence electrons, two in the S subshell and two in the P subshell.
If only IMFs/attractions are broken/formed, than is it likely a physical or chemical change?
Physical change
~leaving the basic chemical unit of a substance unchanged making physical
Why is the heat of vaporization greater than the heat of fusion?
because more energy needed to overcome all IMF's
N2(g) + 3H2(g) -> 2NH3(g)
What is the expression for the equilibrium constant,Kp , for the reaction represented above?
Kp = (PNH3)^2)/(PN2)(PH2)^3)
Kp = (PC)^c(PD)^d/(PA)^a(PB)^b
How do you solve an acid-base titration problems
1. Write balanced eqn.
2. determine inital mol of each species
3. Use ICE table IN MOLES to determine changes in mol amounts
4. Find pH based on equilibrium conditions
4a. Acid and salt only: use Ka or H-H eqn
4b. salt only (stoich ratio of acid and base): hydrolysis -> [OH-] -> pH
4c. excess base and salt (no acid remains): ignore hydrolysis, [OH-] -> pH
Based on intermolecular forces what will have a higher boiling point Cl2 or HCl?
Cl2
~Cl2 is a larger nonpolar molecule, which means it has stronger London dispersion forces, resulting in a higher boiling point
What compounds do you NOT split up to write a net ionic eqn?
Covalent compounds, weak base/acids, liquids, solids, insoluble ionics
~while insoluble salts and weak acids should remain as one unit.
NO2(g) + NO3(g)->N2O5(g)
The reaction represented above occurs in a single elementary step. The activation energy for the step is 18 kJ/mol, and the overall energy change is -136 kJ/mol,
What is the activation energy for the reverse step?
154 kJ/mol
you can find this by subtracting the activation energy of the step and the overall activation energy {18kJ/mol-(-136kJ/mol)}
CO(g) + 2H2(g) - CH30H(g)
At 475 K, 0.10 mol each of the three gases in the reaction represented above are placed in an evacuated, rigid 1.0 L container. The value of Kc for the reaction at 475 K is 47. At equilibrium, which of the gases will have the highest concentration?
H2(g)
~Qc > Kc, the system will increase [CO] and [H2] and decrease [CH3OH] until Qc = Kc. Since all three gases have the same initial concentration and that H2 (g) is produced twice as fast as CO (g), this means that H2 will be higher at equilibrium.
PbBr2(l) -> Pb(l) + Br2(g)
In an electrolytic cell based on the reaction represented above, which of the following occurs at the anode?
Bromine is oxidized at the anode.
~determine which element increases in oxidation number over the course of the reaction. the oxidation number of lead decreases from +2 to 0, while the oxidation number of bromine increases from -1 to 0.
Which of the following bonds is likely to have the most ionic character?
Ca-S
P-Cl
K-Cl
Si-S
K-Cl
~For the bigger the electronegativity difference the more ionic the bad is, so K and Cl have the biggest electronegativity difference resulting in the most ionic bond.
At standard temperature and pressure, a 0.50 mol sample of H2 gas and a separate 1.0 mol sample of O2 gas have the same?
average molecular kinetic energy
~the average kinetic energy depends upon the absolute temperatureonly. Since the temperature is the same for both gases, so their average kinetic energy will also be the same.
The rate law for a particular reaction is rate= k[XY]^2 . In an experiment, the initial rate of the reaction is determined to be 0.16 mol/L(s) when the initial concentration of XY is 0.40 mol/L.
What is the value of the rate constant,K, for the reaction?
1.0 L/mol(s)
k = rate/[XY]^2
k=.16/.40^2
Cu (ag) + Br (ag) → CuBrag)
K1 = 2 × 108
CuBraq) + Br (aq) → CuBiz (ag)
K2 = 4 × 10-3
Given the values of K1 and K2 for the reactions represented above, what is the value of K3 for the following reaction?
Cut (ag) + 2 Br (ag) = CuBiz (aq)
Кз — ?
K3= 8*10^5
~K3=K1*K2
A 30.0 mL sample of 0.020 M HIaq) is added to 95.0 mL of distilled water.
Calculate the pH of the resulting solution.
pH=2.32
1-Find the concentration of H30+
M2=M1V1/V2
=.0048M
2- convert from H30+ to pH using the equation for pH
pH=-log(H30+)
A 152g sample of a compound contains 48g of C, 8g of H, and 96g of O - Which of the following is the empirical formula of the compound?
-CH2O3
-C2H4O3
-C2H4O6
-C4H8O6
C2H4O3
A gas mixture at 0°C and 1.0atm contains 0.010mol of H2, 0.015mol of O2, and 0.025molof N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture?
0.20atm
~Partial pressure = (total absolute pressure) × (volume fraction of gas component)
A polystyrene cup initially contains 10g of water at a temperature T1. A 10g lead weight at a higher temperature T2 is added to the cup, and the mixture is allowed to reach thermal equilibrium.
Which of the following is true of the final temperature of the system at thermal equilibrium? (The specific heat of water is 4.2 J/(g)C, and the specific heat of lead is .13 J/(g)C)
the final temperature is closer T1 then T2
~Since water has a greater specific heat than lead, the temperature change in the water will be smaller than the temperature change in the lead
12(9) + C12 (g) = 2ICIg)
Kp = 231 at 800 K
A rigid vessel initially contains I2 (g) and C12 (g), each at a partial pressure of 1.20 atm at 800 K. The system comes to equilibrium according to the equation above. Calculate the partial pressure of ICIg) in the vessel at equilibrium at 800 K. Write your answer using three significant figures.
2.12 Atm
~Set up an ice table to create a K constant to find the change or X which is 1.06 and then use X to find partial pressure of ICIg) which is = 2X
Sn2+ (aq) + 2 Cl (aq) → Sn(s) + CL,(g)
An electrolytic cell is constructed based on the reaction represented above. The standard potential for the cell at 298 K is -1.50 V.
Calculate the value of delta G, in kJ/mol for the cell reaction at 298K
298 K.
Write your answer using three significant figures.
kJ/molran
289 kJ/mol
~delta G=-nFE
-(2)(96,485)(-1.5)/1