What is the connection between the Pauli Exclusion principle, the Aufbau principle, the indeterminacy of fermions, electron configurations and quantum numbers. Why is shielding more effective for electrons in orbitals with lower principal quantum number than for electrons within the same shell?
In: Chemistry
Gas chromatography and the quantitative method of standard addition to constant volume were used to investigate the concentration of 2,4‑dichlorophenoxyacetic acid (a chlorinated phenoxy herbicide) in a water sample from Lake Eildon.
Liquid-liquid extraction using dichloromethane was used to extract 1.00 L of water sample and the combined extracts were made up to 25 mL in a volumetric flask. A 5.00 mL aliquot of the combined extract was added to each of two 10 mL volumetric flasks. To one flask was added 50.00 μL of a 1.150 x 10-4 M standard solution of 2,4‑dichlorophenoxyacetic acid. Both flasks were then made up to the final volume. The GC analysis of 10.00 μL of injected sample from each flask resulted in peak areas of 245 mV.s and 290 mV.s for the signal in the chromatograms due to 2,4‑dichlorophenoxyacetic acid.
(Relative molar mass of 2,4-dichlorophenoxyacetic acid = 221.04 g.mol-1)
(i). Calculate the concentration (mol/L) of 2,4-dichlorophenoxyacetic acid in the working standard solution used for quantitative analysis of the analyte
(ii). Write the standard addition equation and identify the terms to be applied
(iii). Apply the standard addition equation and determine the concentration in mg/L of 2,4‑dichlorophenoxyacetic acid in the original water sample from Lake Eildon
(iv). Identify the likely sources of experimental error in the laboratory method and calculate the percentage error in the value for the concentration of 2,4‑dichlorophenoxyacetic acid determined in (iii) (2 + 4 = 6 marks). Briefly, discuss how you would confirm the validity of the value determined in (iii)
(v). Discuss the likely health risks associated with a concentration of 30 μg/L of 2,4‑dichlorophenoxyacetic acid as compared to typical values found in Australian drinking waters
(vi) Discuss the effectiveness of dissolved oxygen to other common water treatment processes to effectively remove 2,4‑dichlorophenoxyacetic acid from Australian drinking waters
In: Chemistry
The substance HCO3-1 is amphiprotic, meaning is can act as
either an acid or a base. Complete the reactions started below to
show how it acts as an acid and as a base. Label the conjugate acid
and base for each
reaction.
ACID REACTION: HCO3-1 + H2O(l) ?
BASE REACTION: HCO3-1 + H2O(l) ?
In: Chemistry
Hydrogen and methanol have both been proposed as alternatives to hydrocarbon fuels.
A) Write balanced reactions for the complete combustion of hydrogen.
B) Use standard enthalpies of formation to calculate the amount of heat released per kilogram of the fuel.
C) Write balanced reactions for the complete combustion of methanol.
D) Use standard enthalpies of formation to calculate the amount of heat released per kilogram of the fuel.
E) How does the energy of these fuels compare to that of octane (C8H18)? Amount of heat released by octane = ?.
In: Chemistry
Below is a set of data collected
at 0.95 atm
for the formation of CO
2
gas produced when calcium
carbonate is reacted with aqueous HCl:
Time (min)
Volume CO
2
(mL)
1
0.2
0
2
0.3
0
3
0.5
0
4
0.7
0
5
0.9
0
6
1
.00
7
1.2
0
8
1.3
0
9
1.5
0
10
1.7
0
11
1.9
0
12
2
.00
13
2.2
0
14
2.4
0
15
2.5
0
16
2.7
0
17
2.9
0
18
3
.00
19
3.2
0
20
3.4
0
Your assignment is as follows:
1. Create a spreadsheet in Excel (or equivalent) that
contains this data and does the following
calculations
automatically:
a. Converts each gas volume measurement to
moles of CO
2
produced
(Use a
PV = nRT to
solve
). Do this twice: one column for 0
In: Chemistry
6.Suppose you have a solution that contains 0.0420 M Ca2 and 0.0960 M Ag . If solid Na3PO4 is added to this mixture, which of the following phosphate species would precipitate out of solution first?
first part is Ca3(PO4)2
When the second cation just starts to precipitate, what percentage of the first cation remains in solution?
______ %
In: Chemistry
Calculate the vapor pressure at 25 C of an aqueous solution that
is 5.50% NaCl by mass. (Assume complete dissociation of the
solute)
Please explain thoroughly.
In: Chemistry
How much heat (in kJ) is required to warm 11.0 g of ice, initially at -13.0 ∘C, to steam at 113.0 ∘C? The heat capacity of ice is 2.09 J/g⋅∘C and that of steam is 2.01 J/g⋅∘C.
In: Chemistry
A 200.00mL sample of 1.000M nitric acid is added to a carbonate buffer solution prepared by mixing 1.00mol Na2CO3 and 1.000 mol NAHCO3 and adding water to make a 1.000L solution. What is the resulting pH? (pKa of HCO3- is 10.32)
In: Chemistry
A) A 50.0-mL volume of 0.15 M HBr is titrated with 0.25 M KOH. Calculate the pH after the addition of 19.0mL of KOH.
Express your answer numerically.
B) A 75.0-mL volume of 0.200 M NH3 (Kb=1.8�10?5) is titrated with 0.500 M HNO3. Calculate the pH after the addition of 13.0mL of HNO3.
C) A 52.0-mL volume of 0.35 M CH3COOH (Ka=1.8�10?5) is titrated with 0.40 M NaOH. Calculate the pH after the addition of 23.0mL of NaOH.
In: Chemistry
Complete combustion of 2.50g of a hydrocarbon produced 8.14g of CO2 and 2.50g of H2O. What is the empirical formula for the hydrocarbon? Insert subscripts as necessary.
In: Chemistry
what are the arrhenius definitions for an acid and base? give a chemical equation to demonstrate a strong acid and a weak acid
In: Chemistry
3. You are hard at work, setting up the apparatus to separate a 40:60 mixture of diethyl ether and toluene by simple distillation. Just as you are getting ready to begin the experiment, your lab partner mistakenly adds a small amount of sodium sulfate into the distillation flask. Would simple distillation still be appropriate or should you switch to fractional distillation? Explain.
In: Chemistry
Phosphoric acid H3PO4 is manufactured by treating mineral phosphates with concentrated sulfuric acid H2SO4. A typical phosphate mineral, Ca5(PO4)3F, reacts with sulfuric acid as shown by the equation:
Ca5(PO4)3F
+
5H2SO4
3H3PO4
+
5CaSO4·2H2O
+ HF
If 5.00 tons of this mineral is treated with 6.00 tons of sulfuric
acid to produce 2.70 tons of
phosphoric acid, what is the percent yield of phosphoric acid?
In: Chemistry
I am having problems with variables on both sides. I get most of the concepts but I need help with adding fractions into the equations.
In: Chemistry