Exam 1
Identify each of the following elements based on the atomic number. Give the number of protons and neutrons in each nucleus.
a. 15
b. 53
c. 19
d. 70
What is:
a. Phosphorus, 15 protons, 16 neutrons
b. Iodine, 53 protons, 74 neutrons
c. Potassium, 19 protons, 20 neutrons
d. Ytterbium, 70 protons, 104 neutrons
Write Lewis structures and predict whether each of the following is polar or nonpolar.
a. SO3
b. SeF4
c. KrF4
What is:
a. Trigonal planar, nonpolar
b. See-saw, polar
c. Square planar, nonpolar
Assign the oxidation state for the element listed in each of the following compounds:
a. S in MgSO4
b. Pb in PbSO4
c. O in O2
What is:
a. +6
b. +2
c. 0
For the reaction:
2H2O(g) <--> 2H2(g) + O2(g)
K= 2.4*10-3 at a given temperature. At equilibrium in a 2.0 L container, it is found that [H2O(g)] = 1.1*10-1 M and [H2(g)] = 1.9*10-2 M. Calculate the moles of O2(g) present under these conditions.
What is 0.16 mol O2(g)?
Is an aqueous solution of NaHSO4 acidic, basic, or neutral? What reaction occurs with water?
What is acidic?
HSO4- <--> SO42- + H+
For each of the following pairs of elements, choose the one that has the higher ionization energy.
a. K and Cs
b. Te and Br
c. Ge and Se
What is:
a. K
b. Br
c. Se
Write the Lewis structure of N2O (including resonance forms). Give the formal charge on each atom and the hybridization of the central atom.
What is sp hybridization?
The total volume of hydrogen gas needed to fill the Hindenburg was 2.0*108 L at 1.0 atm and 25oC. Given that delta Hfo for H2O(l) is -286 kJ/mol, how much heat was evolved when the Hindenburg exploded, assuming all the hydrogen reacted to form water?
What is 2.3*109 kJ?
At a particular temperature, 12.0 moles of SO3 is placed into a 3.0 L rigid container, and the SO3 dissociates by the following reaction:
2SO3(g) <--> 2SO2(g) + O2(g)
At equilibrium, 3.0 moles of SO2 is present. Calculate K for this reaction.
What is 0.056?
0.0070 M HNO3 and 3.0 M KOH
What is 0.0070 M and 2.15 for HNO3; 3.33*10-15 M and 14.48 for KOH
Arrange the atoms and/or ions in the following groups in order of decreasing size.
a. O, O-, O2-
b. Fe2+, Ni2+, Zn2+
c. Ca2+, K+, Cl-
What is:
a. O2- > O- > O
b. Fe2+ > Ni2+ > Zn2+
c. Cl- > K+ > Ca2+
In which of the following diatomic molecules would the bond strength be expected to weaken as an electron is removed?
a. H2
b. B2
c. C22-
d. OF
What is H2 (a), B2 (b), and C22- (c)?
Rationalized the difference in boiling points for each of the following pairs of substances:
a. HF = 20oC; HCl = -85oC
b. HCl = -85oC; LiCl = 1360oC
What is:
a. HF is capable of hydrogen bonding, while HCl is not.
b. LiCl is ionic and HCl is a molecular solid with only dipole forces and London dispersion forces. Ionic forces are much stronger than the forces for molecular solids.
An important reaction in the commercial production of hydrogen is:
CO2(g) + H2O(g) <--> H2(g) + CO2(g)
How will this system at equilibrium shift in each of the five following cases?
a. gaseous carbon dioxide is removed.
b. water vapor is added.
c. in a rigid reaction container, the pressure is increased by adding helium gas.
d. the temperature is increased (the reaction is exothermic)
e. the pressure is increased by decreasing the volume of the reaction container
What is:
a. Right
b. Right
c. No effect
d. Left
e. No effect
What is the concentration of [OH-] and the pOH for the following solutions?
0.0070 M HNO3 and 3.0 M KOH
What is 1.4*10-12 M and 11.85 for 0.0070 M HNO3; 3.0 M and -0.48 for KOH
What is 4.104*10-7 m?
A given sample of xenon fluoride compound contains molecules of the type XeFn, where n is some whole number. Given that 9.03*1020 molecules of XeFn weigh 0.368 g, determine the value for n in the formula.
What is 6 F?
Diethyl ether (CH3CH2OCH2CH3) was one of the first chemicals used as an anesthetic. At 34.6oC, diethyl ether has a vapor pressure of 760. torr, and at 17.9oC, it has a vapor pressure of 400. torr. What is the delta H of vaporization for diethyl ether?
Suppose K = 4.5*10-3 at a certain temperature for the reaction:
PCl5(g) <--> PCl3(g) + Cl2(g)
If it is found that the concentration of PCl5(g) is twice the concentration of PCl3(g), what must be the concentration of Cl2(g) under these conditions?
What is 0.009 M
Acrylic acid is a precursor for many important plastics. Ka for acrylic acid is 5.6*10-5. Calculate the pH of a 0.10 M solution of acrylic acid.
What is 2.63?
Give the maximum number of electrons in an atom that can have these quantum numbers:
a. n = 4
b. n = 5, ml = +1
c. n = 5, ms = 1/2
d. n = 3, l = 2
e. n = 2, l = 1
What is:
a. 32
b. 8
c. 25
d. 10
e. 6
An element X forms both a dichloride (XCl2) and a tetrachloride (XCl4). Treatment of 10.00 g XCl2 with excess chlorine forms 12.55 g XCl4. Calculate the atomic mass of X, and identify X.
What is 207.14 g/mol; Pb?
In a coffee-cup calorimeter, 150.0 mL of 0.50 M HCl is added to 50.0 mL of 1.00 M NaOH to make a 200.0 g solution at an initial temperature of 48.2oC. If the enthalpy of neutralization for the reaction between a strong acid and a strong base is -56 kJ/mol, calculate the final temperature of the calorimeter contents. Assume the specific heat capacity of the solution is 4.184 J/goC and assume no heat is lost to the surroundings.
What is Tf = 51.5oC?
At 2200oC, Kp = 0.050 for the reaction:
N2(g) + O2(g) <--> 2NO(g)
What is the partial pressure of NO in equilibrium with N2(g) and O2(g) that were placed in a flask at initial pressures of 0.80 and 0.20 atm, respectively?
Consider a 0.67 M solution of C2H5NH2 (Kb = 5.6*10-4).
Which of the following are the major species in the solution: C2H5NH2, H+, OH-, H2O, C2H5NH3+?
Calculate the pH of this solution.
What is C2H5NH2 and H2O; 11.28?