You have 875 mL of an 0.39 M acetic acid solution. What volume (V) of 1.70 M NaOH solution must you add in order to prepare an acetate buffer of pH = 4.36? (The pKa of acetic acid is 4.76.)
In: Chemistry
(a) How many grams of CaCl2 are needed to make 250.9 g of a solution that is 30.5% (m/m) calcium chloride in water? Note that mass is not technically the same thing as weight, but (m/m) has the same meaning as (w/w).
-How many grams of water are needed to make this solution?
(b) What is the volume percent % (v/v) of an alcohol solution made by dissolving 117 mL of isopropyl alcohol in 747 mL of water? (Assume that volumes are additive.)
(c) The mass of solute per 100 mL of solution is abbreviated as % (m/v). (The abbreviation % (w/v) is also common.) How many grams of sucrose are needed to make 735 mL of a 34.0% (w/v) sucrose solution?
In: Chemistry
Consider the following reaction. 2NO2(g)⇌N2O4(g) When the system is at equilibrium, it contains NO2 at a pressure of 0.722 atm, and N2O4 at a pressure of 0.0521 atm. The volume of the container is then reduced to half its original volume. What is the pressure of each gas after equilibrium is reestablished?
PNO2= ?? atm
PN2O4= ?? atm
In: Chemistry
Part C
Go to the Phase Changes tab. Select the particular molecule, and set the temperature to the given values by using the stove to increase or decrease the temperature. Increase the pressure of the cylinder by moving the lid of the cylinder down with the help of the finger. The pressure of the cylinder is indicated by the pressure gauge on the top left corner of the simulation. On the right-hand side of the simulation is the phase diagram for the molecule.
As the molecules collide on the walls of the cylinder, the pressure of the cylinder does not remain constant; it fluctuates slightly as indicated by the gauge.
In the phase diagram, observe the red point. When a particular molecule is selected, set the temperature and pressure condition to the required value. Observe the position of the red point on the phase diagram when the pressure reaches approximately near the required value.
Which of the following conditions will result in the formation of a supercritical fluid?
Check all that apply.
| 1. | Oxygen at 100 K and no pressure |
| 2. | Argon at 160 K and approximately 6 atm pressure |
| 3. | Water at 294 K and approximately 1 atm pressure |
| 4. | Neon at 32 K and approximately 1 atm pressure |
| 5. | Neon at 50 K and approximately 10 atm pressure |
| 6. | Water at 894 K and approximately 20 atm pressure |
| 7. | Argon at 100 K and no pressure |
| 8. | Oxygen at 194 K and approximately 2 atm pressure |
In: Chemistry
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