Polyprotic Acids/bases
What is the predominant species of carbonic acid (H2CO3) at a pH of 6.5? (Ka1 = 4.5 x 10-7 , Ka2 = 4.7 x 10-11)
HCO3-
What is the pH at the equivalence point of a strong acid and strong base titration?
7.00
What is the volume of 0.100 M NaOH needed to reach the last equivalence point when titrated with 20.0 mL of 0.100 M phosphoric acid (H3PO4)
Eq 3 = 60.0 mL NaOH
EDTA forms _______ complexes with any metal regardless of charge
1:1
Determine the energy per mole of photons of a light that has a wavelength of 1.00 x 103 nm.
A. 20. kJ/mol
B. 120. kJ/mol
C. 100. kJ/mol
D. 150 kJ/mol
B. 120. kJ/mol
What is the pH of 1.00 M Carbonate (CO32-) solution at 25 0C ? (ignore activities) Ka1 = 4.5 x 10-7; Ka2 =4.7 x 10-11
12.16
Consider the titration of 100.0 mL of 0.100 M Hydrochloric acid with 0.100 M sodium hydroxide. What is the pH when 99.0 mL of sodium hydroxide have been added?
3.299
Citric acid is a triprotic acid abbreviated H3A. A 0.125 M sample of citric acid is titrated with 0.250 M LiOH. What is the pH halfway to equivalence point 1, halfway to equivalence point 2, and halfway to equivalence point 3? (Ka1 = 7.1 x 10-4, Ka2 = 1.7 x 10-5, Ka3 = 6.4 x 10-6)
Halfway to eq. 1, pH = 3.15
Halfway to eq. 2, pH = 4.77
Halfway to eq. 3, pH = 5.19
The _______ form of EDTA is the only species that binds to metal to form metal-EDTA chelate
Y4- (the basic form)
Predominant at high pH
Which of the following statements is FALSE ?
A. Atoms undergo electronic transitions but not rotational or vibrational transitions
B. Typically, IR radiation causes vibrational transitions of molecules
C. Compared to IR, UV radiations have longer wavelengths and less energy
D. Shorter the wavelength of a radiation higher the frequency
C. Compared to IR, UV radiations have longer wavelengths and less energy
Calculate the pH of the resultant buffer if 7.00 g of Na2CO3 (105.99 g/mol) and 5.00 g of NaHCO3 (84.01 g/mol) are dissolved in 1000.0 mL of solution. Ka1 and Ka2 for H2CO3 are 4.5 x 10-7 and 4.7 x 10-11
pH = 10.374
What volume of NaOH must be added to reach the equivalence point for the titration of 0.100 M NaOH and 50.0 mL of 0.0500 M HCN (HCN is a weak acid)?
25.0 mL NaOH
Citric acid is a triprotic acid abbreviated H3A. A 0.125 M sample of citric acid is titrated with 0.250 M LiOH. What is the pH at equivalence point 1 and equivalence point 2 (Ka1 = 7.1 x 10-4, Ka2 = 1.7 x 10-5, Ka3 = 6.4 x 10-6)
@ eq. 1 = 3.96
@ eq. 2 = 4.98
Calculate the conditional formation constant (K'f) for an EDTA titration with Li+ at pH 12. (logKf = 2.95 , alphaY4- = 0.98)
K'f = Kf x alphaY4-
K'f = (102.95) x (0.98) = 870
You are running an experiment to determine the protein concentration of an unknown sample using BCA. When you go to measure the absorbance of your sample, your spectrometer is on the fritz and only can only measure the %transmittance of your sample. You measure your sample and the measured %transmittance is 25%. What is the absorbance of your sample?
Absorbance = 0.60
6.015
Consider the titration of 10.0 mL of 0.100 M HF (pKa 3.19) with 0.100 M sodium hydroxide. What is the pH of the solution at the equivalence point?
pH = 7.944
Consider the titration of 10.0 mL of 0.100 M weak acid H2A (pKa1 1.92, pKa2 6.27) with 0.100 M NaOH. What is the pH when 20.0 mL of NaOH has been added?
pH = 9.60
What is an auxilliary complexing agent?
An agent that binds to the metal ions to prevent formation of metal hydroxides which would precipitate out of solution.
Kf for auxilliary complexing agent must be lower than the Kf for the EDTA
Which of the following is True?
A. Fluorescence is slower than phosphorescence
B. Intersystem crossing only occurs in fluorescence
C. Fluorescence and phosphorescence are types of absorption
D. Fluorescence occurs at a higher energy than phosphorescence in the same molecule
D. Fluorescence occurs at a higher energy than phosphorescence in the same molecule