What are the odds?
Give the answer to the following calculation with the correct number of significant figures.
41.84 × 100.62 × (15.227 – 15.134)
390
What is the denticity of EDTA?
hexadentate
What does LASER stand for?
light amplification by stimulated emission of radiation?
What terms of the van Deemter equation are zero in:
GC
LC
CE
GC: A term is zero
LC: No terms are zero
CE: A and C terms are zero
Convert 4.0 km2 to square miles.
Some or all of these or all of these relations might be useful:
1 in = 2.54 cm; 1 ft = 12 in; 1 mi = 5 280 ft
1.5 mi2
You prepare an NH3 [FM 17.0305 (±0.0002)] solution by diluting 7.36 (±0.03) mL of a 28.00 (±0.05) wt% NH3 solution [density = 0.899 (±0.003) g/mL] to a final volume of 500.00 (±0.02) mL. Find the molarity of the NH3 solution along with its absolute uncertainty.
0.2176 (+/–) 0.0012 M
Calculate the pH of a 0.0040 M HCN solution.
Ka = 6.2 × 10−10
5.80
What is a non-radiative transition between states with different spin called?
intersystem crossing
Calculate the resolution of two compounds separated using gas chromatography. The retention times were 628 and 642 s, and the widths at half-height were 8.3 and 9.4 s, correspondingly.
0.93
What is the molecular geometry and polarity of chlorine trifluoride?
T-shaped and polar
The following molarities were calculated from replicate standardizations of a NaOH solution: 0.502 8, 0.502 9, 0.502 3, 0.503 1, 0.502 6, 0.502 7, 0.503 4, and 0.502 5. Assuming no systematic errors, within what range are you 90% certain that the true mean value of the molarity falls?
t = 1.895
0.5026–0.5030 M
Calculate the thermodynamically correct pH of a solution containing 0.0050 M NaOH and 0.0090 M KCl.
The hydrated radius of OH– is 350 pm.
11.65
How many minutes will it take to deposit 0.250 g of copper on a platinum electrode from a solution of Cu(NO3)2 at a constant current of 0.500 A?
25.3 min
A solute with a distribution constant of 6.5 is extracted from 15 mL of phase 1 into phase 2. What is the total volume of solvent 2 needed to remove 99.9% of the solute in one extraction?
2300 mL
What is the free-energy change (in kJ/mol) for the reaction:
Cu(𝑠) + Mg2+ (𝑎𝑞) → Mg(𝑠) + Cu2+ (𝑎𝑞)
Helpful data:
Cu2+(aq) + 2e− → Cu(𝑠) Eo = 0.34 V
Mg2+(aq) + 2e− → Mg(𝑠) Eo = −2.37 V
522.9 kJ/mol
A study of body mass index (BMI) in adults showed that for men aged 40–44, the mean BMI level is 26.7 with a standard deviation of 3.7. Assuming a normal distribution, what percentage of men in this age group have a BMI between 30.0 and 35.0?
17%
A 25.0-mL solutions of 0.100 M Ba2+ is titrated with 0.100 M EDTA at pH 8. Calculate the value of pBa2+ after the addition 25.0 mL of titrant.
log Kf = 7.88
α = 0.0042
3.40
A calcium ISE with a selectivity coefficient for sodium of 0.0045 is placed in a solution with a calcium activity of 0.000285 M and the measured potential is 427.4 mV. What will be the activity of sodium in solution if this same electrode is placed in a solution with a the same calcium activity and reads a voltage of 430.3 mV?
0.125 M
Which compound would elute last in normal-phase liquid chromatography?
decane bromobenzene benzene
heptanol ethylene glycol
ethylene glycol
What is the energy (in kJ/mol) of light with a wavelength of 508 nm.
235.48 kJ/mol
The amount of copper in an unknown solution was measured using atomic absorption (AA) spectroscopy. The solution gave an absorbance of 0.215. Then a 25.00-mL aliquot of the solution was pipetted into a 50-mL beaker, and 5.000 mL of 100.0-ppm Cu2+ standard were added and mixed. The absorbance of this solution was 0.358. What was the concentration of copper in the original unknown solution?
20.0 ppm
Consider a diprotic acid (H2A) with pKa1 = 7.301 and pKa2 = 10.00. A 40.0-mL sample of a 0.050 M solution of the disodium salt of this acid (Na2A) is titrated with 0.100 M HCl. Calculate the pH after 20 mL of titrant has been added.
8.65
A 30.0-mL aliquot of 0.00200 M KMnO4 is titrated with 0.0200 M Fe2+ in 1.00 M HNO3 using a platinum electrode. Calculate the potential 5.0 mL before the equivalence point. The relevant half-reactions are:
MnO4– + 8 H+ + 5 e– --> Mn2+ + 4 H2O Eo = 1.507 V
Fe3+ + e– --> Fe2+ Eo = 0.746 V
1.306 V
Chromatography is divided into five categories on the basis of the mechanism of interaction of the solute with the stationary phase. What are the five categories?
adsorption, partition, ion-exchange, size exclusion, and affinity
Calculate the molarity of a 70.0 wt% perchloric acid solution with a density of is 1.664 g/mL.
(MW = 100.46 amu)
11.6 M