2.4. A 2.3 L cylinder containing nitrogen gas at a pressure of 2.8 atm is connected to a 5.5 L
r containing nitrogen at 17.3 atm. What is the final pressure when both the cylinders have achieved equilibrium (reached the same pressure)?
6. An analytical procedure requires a solution of chloride ions. How many grams of BaCl2 must be dissolved to make 360 ml of 0.2 M Cl– ?
(M BaCl2 = 208 g/mol)
7. Find the concentration of chloride ions when 344.4 mL of 2.4 M NaCl is mixed with 364 mL of 2.9 M KCl?
8. A sample of an unknown gas had a density of 1.45 g/L at 20.5 °C and 1.2 atm. Calculate the molar mass of the gas.
(R = 0.08206 L·atm·mol-1·K-1)
3.a) Carbon tetrachloride is an organic compound with the chemical formula CCl4. It is a
colorless liquid with a “sweet” smell.
quid with a “sweet” smell.
i. Using the ground state electron configuration and excited state electron
configuration explain the hybridization of the central Carbon (C) atom. (7 Marks)
ii. Identify the orbitals that overlap to form the C-Cl bond. Draw a diagram to show
the orbital overlap. (3 Marks)
iii. What is the bond angle of CCl4? (1 Mark)
b) Consider a Fluorine atom (F) and a Fluorine anion (F-). Which of these two species would
you expect to have a larger radius? Explain your answer. (5 Marks)
c) Explain why the first ionization energy of Aluminum (Al) is less than that of Magnesium
(Mg). (4 Marks)
d) Assume the atom Oxygen(O) can form both cationic(O+) and anionic(O-) species. Place
the following species in order of increasing first ionization energy, starting with the lowest.
O+, O, O-
a) Sea water contains roughly 28.0 g of NaCl per liter. (NaCl molar mass = 58.44 gmol-1).
i. Calculate the number of moles of NaCl in a liter of sea water. (2 Marks)
ii. Calculate the molarity of NaCl in sea water. (4 Marks)
iii. Calculate the mass by volume percent (W/V) of NaCl in sea water. (4 Marks)
5.AP Chem AB FRQ
A sample consisting of 50. mL of 0.400 M solution of the acid, HClO4, is titrated
titrated with a 0.200 M solution of the base, LiOH.
Write the balanced chemical reaction for neutralization reaction:
HClO4 (aq) + LiOH (aq) → LiClO4 (aq) + H2O (l)
Write the NET ionic equation for the neutralization reaction.
OH⁻ (aq) + H⁺ (aq) → H2O (l)
Compute the pH of the titration solution. Show your work
i) before any of the base is added
ii) after 25. mL of base is added
iii) after 50. mL of base is added
A student performs the titration with the same chemicals but with smaller volumes of each chemical . Which of the following titration curves could represent the titration. Explain
A because this entails a strong acid and a strong base.
A student performs a titration of an unknown acid with a strong base and gets the following titration curve:
a) The student consults the list of pKa of acids shown below. If the acid is listed in the table below, which is the most likely identity of the unknown acid? Explain.
7.2 x 10-4
1.8 x 10-5
4.3 x 10-7
2.0 x 10-9
The unknown acid is HBrO because the calculated Ka is in between 50^-4 and 50^-6 and 2.0 x 10^-9 lies in between them.
b) What is the initial molarity of the acid?
10^-3 = 0.001M
a) Describe the components and the composition of an effective buffer solution. Explain how the components of the buffer allow the buffer to maintain its pH.
An effective buffer solution has a weak acid and its conjugate base or a weak base and its conjugate acid. A buffer solution is most effective when the ratio of its component concentrations is close to 1, also when the pH is equal to the pka of the acid.; The components of the buffer allow the buffer to maintain its pH because buffers can absorb excess H+ions or OH– ions.
An employer is interviewing four applicants for a job as a laboratory technician and asks each how to prepare a buffer solution with a pH of 5.0. The following constants may be helpful: hydrazoic acid, pKa = 4.74 Boric acid, pKa = 9.23
Archita A. says she would mix equal molar solutions of hydrazoic (HN3) and sodium azide (NaN3) solutions.
Bradley B. says she would mix equimolar Boric acid (H3BO3) and HCl solutions.
Carlos C. says he would mix equimolar Boric Acid (H3BO3) and sodium dihydrogen borate (NaH2BO3) solutions.
Delia D. says he would mix equimolar hydrazoic Acid (HN3) and NaOH solutions.
b) Which of these applicants has given an appropriate procedure? Explain your answer
Delia because she is using Sodium hydroxide which results in a pH of 5. NaOH is a strong base and in order to have an effective buffer a weak acid must be incorporated which is the HN3.
c) Explain what is wrong with the erroneous procedures.
The rest all incorporate a strong acid and a strong base or a weak acid and a weak base which don’ result in an effective buffer.
d) The applicants have access to the 1 Liter volumes of each of the solutions listed above. They have access to graduated cylinders. In order to make 1.0 Liter of the correct 5.0 buffer solution, what volumes of the two chemicals must be mixed?
8.1) A hypothetical element exists as two isotopes: I = 42.00 amu and II = 49.00 amu. If the percent
bundance of isotope I is (1.94x10^1)%, what would be the calculated atomic mass (in amu)?
2) A hypothetical element exists as two isotopes: I = 78.00 amu and II = 84.00 amu. If the atomic mass of this element is found to be 80.33 amu, which isotope must be more abundant?
3) If the hypothetical polyatomic ion ThOM2- is called "thomite", what would be the formula and name of the acid formed by this ion?
4) How many atoms of hydrogen are there in a sample of (4.00x10^2) grams of NH3(g)?
5) How many O (oxygen) atoms are there in (6.40x10^2) grams of H3PO4?
6) How many moles of fluorine atoms are there in (5.80x10^2) grams of SF4?
7) When 3.50 g of titanium (Ti) reacts with oxygen, the resulting oxide compound weighs 5.84 g. What is the empirical formula of this oxide?
8) How many moles of molecules are there in (6.70x10^2) grams of CH4?
9) A chemical is found to be 80.0% C and the rest is H. If the molar mass of this chemical is known to be 90.2 g/mol, what is the molecular formula?