Chem diag 1
In the span of two hundred minutes, 30 grams of copper is plated on a sample of iron with a constant current of 3.8 A. How many moles of electrons are transferred per mole of plated copper? Note: F = 96,500 C/mol e-
1 mole
what is the maximum number of electrons that can fill the f subshell?
14 because it has seven orbitals
Which of the following statements about solids is true? A. The intramolecular bonds of a molecular solid are the same as its intermolecular forces. B. Ionic solids have a lower melting point than molecular solids. C. Network solids have greater electrical conductivity than metallic solids. D. Unlike network solids, metallic solids are ductile.
D
When is the reaction quotient equal to the equilibrium constant?
When ΔG = 0
increasing reactant concentration increases reaction rate by doing what?
increasing probability of a collision
which has the greatest radius? Br- Kr Rb+ Sr2+
Br- negative ions have greater size
Which of the following best explains why gases behave less ideally at higher pressures?
Molecular interaction occurs to a greater degree.
least stable products of an electrolytic cell
most negative E
which is true when heat is added to a system?
temperature may increase or it may remain unchanged
An expanding gas in an adiabatic piston cylinder system:
cools because internal energy is decreasing.
which is true about the amount of shielding the highest energy electrons of calcium and arsenic experience?
electrons of calcium have lesser amount of shielding than electrons of arsenic
which of the following changes to an equilibrated system is most likely to change the proportion of reactants and products at equilibrium? increasing activation energy increasing product stability increasing reaction concentration increasing reaction rate
increasing product stability
if deltaG of a reaction increases following an increase in temperature. what impact will this have on the equilibrium constant?
it decreases
which of the following will have the strongest ionic force with a chloride ion? magnesium potassium calcium sodium
magnesium Coulomb's Law states that the force between two charged particles can be explained by the equationF = (k*q1*q2)/r2, where k is a constant, q1 and q2are the magnitude of the charges, and r is the distance between the charges. Since Ca and Mg have larger charges (+2) compared to Na and K (+1), they will have a greater attractive force with chloride, so eliminate choices B and D. As the distance r between the charges increases (with increasing ionic radius), the attractive force between the charges decreases. Magnesium is a smaller ion than calcium since it is higher on the periodic table, so choice C can be eliminated.
2NO + O2 to 2NO2
rate = -(1/2)[NO]/time
The combustion of methane is given by the reaction: CH4 + 2 O2 ➔ CO2 + 2 H2O If 20 moles of methane and 20 moles of oxygen are initially present, how many moles of carbon dioxide are produced?
10
Pure acetic acid freezes at a temperature of 16.6°C. If the kf for acetic acid is 3.90 °C/m, what is the freezing point of a solution made from 8.0 g CH3OH dissolved in 500 g acetic acid? 14.6°C 15.6°C 16.6°C 18.6°C
14.6 The freezing point of a solution is depressed compared to the freezing point of the pure solvent. Therefore, choices C and D can be eliminated. The amount the freezing point is depressed by can be calculated by the following expression: ΔT = kf i m. Since methanol is a non-electrolyte, its van't Hoff factor is 1. To find the molality of the solution: 8 g x 1/32 = 0.25 mol CH3OH m = mol solute/kg solvent = 0.25 mol/0.5 kg = 0.5 m T = (3.9)(0.4)(1)= 2C freezing point is depressed by 2
A cook picked up a pan on the stove and, realizing it was too hot, quickly threw it into a nearby pot on the counter filled with water (at 99.9°C). After treating his hand for the burn, he found approximately one liter of water had vanished. Assuming no heat exchange with the surroundings, approximately how much energy did the pan lose in the vaporization of the water? [Note: ΔHvap (water) = 40.6 kJ/mol]
2200 kJ we would expect 40.6 kJ/mol * 55.5 moles to result in approximately 2200 kJ of energy required to vaporize one liter of water
what is the final pH after 30 mL of 3x10^-3 M HBr is mixed with 20 mL of 4 x 10^-3 M NaOH?
3.7 Here we have (0.03 L)(3 x 10-3 M) = 9 x 10-5 mol H+ and (0.02 L)(4 x 10-3 M) = 8 x 10-5 mol OH- resulting in 1 x 10-5 mol of H+ remaining. This means the solution should be acidic, so we can eliminate choices C and D. The final proton concentration is 1 x 10-5 mol/0.05 L = 0.2 x 10-3 = 2 x 10-4 M H+ resulting in a pH of 3.7 (choice B is correct).
What is the final phase of a 36 g water vapor sample at 400°C after removal of 15 kJ of energy? [Note: ΔHfus and ΔHvap = 6.0 kJ/mol and 40.6 kJ/mol, respectively; c of solid, liquid, and gaseous water = 38.0 J/molˑK, 74.5 J/molˑK, and 36.0 J/molˑK, respectively]
As we are uncertain of the end phase of the water, let us first calculate the amount of energy required to cool the sample to its boiling point. Givenq = mcΔT, we have (2 mol)(36.0 J/molˑK)(300 K) = 21,600 J, or 21.6 kJ, which is far more energy than the amount we removed. Thus, no phase change takes place (choice D is correct). Choice A could have been eliminated before doing any calculations because aqueous is not a phase, but describes a solution in which a solute is surrounded by water.
A sample of nitrogen gas is cooled from 80°C to 20°C in a rigid-walled container. What impact would this have on pressure?
Decrease to 0.8 times the original pressure
which bond is most polar? C-Si H-Cl N-O F-F
H-Cl most polar bond is the one with greatest electronegativity difference
what percentage of HF (pka = 3.17) dissociates in one liter of a solution containing 2 mol of the acid?
HF = H+ + F- x^2/2=10^-3.17
If weights are added to a well-insulated piston cylinder, what are the signs of heat and work for this process?
Heat is zero, work is positive
What is the relationship between the mass of an atom and the sum of the masses of its constituent particles?
The sum of the masses of the constituent particles is greater.
A researcher places a sample of radiolabeled AgI into a saturated solution of non-radiolabeled AgI and several hours later inadvertently spills some of the liquid on a nearby countertop. Is the researcher in danger while cleaning this spill?
Yes, a portion of the radioactive iodide in the solid would have been replaced by the non-radiolabeled isotope.
Which of the following solutions will have the highest freezing point? 0.1 M KCl 0.2 M NH3 0.1 M H2SO3 0.2 M CH3OH
0.1 M H2SO3
Rank the following species by increasing boiling point. I. CH3CHO II. F2 III. CH3OH IV. KBr
II < I < III < IV Coulomb's Law states that the force between two charged particles can be explained by the equationF = (kq1q2)/r2, where k is a constant, q1 and q2 are the magnitude of the charges, and r is the distance between the charges. When comparing molecules, the weaker intermolecular forces occur between molecules with a lesser magnitude of charge. The charge (or partial charge) is due to polarity, which occurs due to differences in electronegativity. KBr will have ionic forces, the strongest option, because of the full charges on the K+ and Br- ions (choice B is correct). F2 is a nonpolar molecule and will form instantaneous-induced dipoles (also known as London dispersion forces), the weakest of all intermolecular forces (choices A and C are wrong). CH3OH and CH3CHO are both polar molecules, but methanol is able to hydrogen-bond due to the -OH group, while weaker dipole-dipole forces hold together the CH3CHO.
