Atomic absorption spectroscopy was used with the method of standard additions to determine the concentration of cadmium in a sample of an industrial waste stream. For the addition, 10.0 μL of a 1000.0 μg/mL Cd standard was added to 10.0 mL of the unknown solution. The results obtained are shown in the table. Absorbance Reagent blank 0.028 Sample 0.480 Sample plus addition 0.887 What is the concentration of the cadmium in the waste stream sample? c = μ g / mL Later, the analyst learned that the blank was not truly a reagent blank, but water. The absorbance of the actual reagent blank, is 0.062 . Calculate the cadmium concentration using the new information for the blank. c = μ g / mL Calculate the percent error caused by using water as the blank instead of the reagent blank. error: %
In: Chemistry
Consider the following reaction:
CO(g)+2H2(g)⇌CH3OH(g)
Kp=2.26×104 at 25 ∘C. Calculate ΔGrxn for the
reaction at 25 ∘C under each of the following conditions.
A) Standard conditions
B) At equilibrium
C) PCH3OH= 1.5 atm ;
PCO=PH2= 1.5×10−2 atm
In: Chemistry
Please make sure to display your thought process? It is imperative to be able to follow how the answer was deduced. Please be as thorough as possible. Please address all parts as they are critical to answering this question correctly:
Discuss the type of surface treatments that are applied to nanoclays in order to improve nanoclay dispersion in polymer matrices. What happens when untreated nanoclay is used to reinforce a polymer? What happens when a properly organically modified clay is used? List and discuss three techniques that are used to characterize the microstructure/nanostructure of nanoclay-filled polymers.
In: Chemistry
1. Manganese(II) (Mn2+) forms a complex with EDTA according to Mn2+ + Y4- <-> MnY2- with a formation constant Kf = 7.8 x 1013.
(a) 23.14 mL of 0.07893 M Mn2+ was titrated with 0.08130 M EDTA at pH 10.00. Calculate the endpoint volume for the titration.
(b) Calculate the conditional formation constant (Kf’) for Mn2+ at pH 10.00 where aY4- = 0.30.
(c) Calculate the concentration of free Mn2+ in solution at the endpoint of the titration at pH 10.00.
(d) Calculate the concentration of free Mn2+ in solution following the addition of 15.00 mL of 0.08130 M EDTA at pH 10.00.
(e) Calculate the concentration of free Mn2+ in solution following the addition of 25.00 mL of 0.08130 M EDTA at pH 10.00.
In: Chemistry
1.921 g of the weak base trimethylamine, (CH3)3N (MW = 59.11g/mol) (Kb = 6.3 x 10-5), is diluted in water to give 50.0 mL of solution. This solution is titrated with 0.10 M HCl. (assume all solutions at 250C)
(a) What is the pH of the original amine solution?
(b) What is the pH of the solution after 162.5 ml of HCl is titrated?
(c) What is the pH after 325ml of HCl is titrated?
In: Chemistry
| Mass of flask, stopper, and 5mL of water (g) | 102.945 | g |
| Mass of flask, stopper, and filled with water (g) | 238.389 | g |
| Volume of gas space in flask (the difference between the above two measurements covnerted to mL) (L) | .135444 | L |
| Trail 1 | Trial 2 | |
| Mass of Mg(g) | 0.008 | 0.007 |
| Initial Pressure (atm) | 0.9974 | 0.9945 |
| Max Pressure (atm) | 0.9980 | 0.007 |
| Pressure Change (atm) | 0.0006 | 0.0471 |
| Temp (K) | 295.7 | 296.1 |
a. Calculate the moles of H2 produced from each trial
b. Vol of gas was not at standard temp and pressure. Convert the volume at the pressure and temperature of the experiment to a volume at standard temperature and pressure. (STP = 273. 15K, P = 1.00atm)
c. Using your answers from part a and b, calculate the molar volume of H2(g) (L/mol) at STP for each trial.
(For what ever reason, I am only able to put in a good value for mols of H2 into the computer, it keeps saying my calculations are incorrect for the rest. Trying to figure out what I am doing wrong)
In: Chemistry
Balance the equations or write the balanced chemical for the
following:
A) C7H8O2(l) + O2(g) → CO2(g) + H2O(g)
B) Copper(II) hydroxide decomposes into copper(II) oxide and water
when heated;
C) Solid calcium carbide, reacts with water to form an aqueous
solution of calcium hydroxide and acetylene gas, C2H2.
D) As2O3(s) + NO3-(aq) → H3AsO4(aq) + N2O3(aq)
In: Chemistry
Calculate the equilibrium constant K of the reaction Sn(s)|Sn2+(aq)||Ag+(aq)|Ag(s) at 25 °C.
In: Chemistry
Consider the titration of 25.0 mL of 0.0500 M Sn2+ with 0.100 M Fe3+ in 1 M HCl to give Fe2+ and Sn4+, using a Pt and calomel electrodes. (a) write a balanced titration reaction (b) write two half-reactions fo the indicator electrode (c) write two Nerst equations for the cell voltage (d) calculate E at the following volumes of Fe3+: 1.0, 12.5, 24.0, 25.0, 26.0, and 30.0 mL. Sketch the titration curve.
In: Chemistry
When a 7.00-g sample of RbBr is dissolved in water in a calorimeter that has a total heat capacity of 3.090 kJ·K–1, the temperature decreases by 0.300 K. Calculate the molar heat of solution of RbBr.
In: Chemistry
What is percent yield fro your synthseis of octyl acetate (acetic anhydride and 1-octanol)? V of ctyl acetate is 1.53 mL.
3 mL of acetic anhydride and 2 mL 1-octanol. One drop of concentrated sulfuric acid.
In: Chemistry
A student dissolved 10.5 g of NH4Cl in 40 mL of water. The temperature of the water changed from 22.5oC to 5.1oC. Calculate the enthalpy of hydration of ammonium chloride in J/mol.
1. A student collected the data below while performing a kinetics experiment.
|
Trial |
Volume of 2.0 M Reactant A |
Volume of 0.5 M Reactant B |
Volume of H2O |
Time for B to react |
|
1 |
10 mL |
10 mL |
30 mL |
135 sec |
|
2 |
20 mL |
10 mL |
20 mL |
69 sec |
|
3 |
10 mL |
20 mL |
20 mL |
34 sec |
Use the above information to complete the following table (enter all answers with 3 significant figures)
|
Trial |
concentration of A |
concentration of B |
Rate for B |
|
1 |
|||
|
2 |
|||
|
3 |
Using the data from the previous problem, determine the order with respect to Substance A. Using the data from Problem 1, determine the order with respect to Substance B. Using the information from Trial 1 and the experimentally determined rate law, determine the value of the rate constant, k for this experiment. Report your answer with 3 significant figures.
Please answer all the questions and with the three significant digits after decimals. Please.
In: Chemistry
Preparing Buffer Solutions: Calculating the Number of Grams of
Conjugate Base Needed
Use the table of K values given with this problem to choose the
best weak acid to start from for making a buffer that holds the pH
of the solution at 3.20. Make your selection so that you maximize
the capacity of the buffer.
You select a 200.0 ml volumetric flask to which you add 54.00 mL of
a 2.90 M solution of the weak acid you just selected. To finish
preparing your buffer you must now add the sodium salt of the
conjugate base. How many grams of the sodium salt of your conjugate
base must you add so that when you finally fill the flask to the
mark with deionized water the buffer will have a pH of 3.20.
| Weak Acid | Ka |
| CH3COOH (Acetic Acid) | 1.8 X 10-5 |
| C6H5COOH (Benzoic Acid) | 6.5 X 10-5 |
| CH3CH2CH2COOH (Butanoic Acid) | 1.5 X 10-5 |
| HCOOH (Formic Acid) | 1.8 X 10-4 |
| HBrO (Hypobromous Acid) | 2.8 X 10-9 |
| HNO2 (Nitrous Acid) | 4.6 X 10-4 |
| HClO (Hypochlorous Acid) | 2.9 X 10-8 |
| CH3CH2COOH (Propanoic Acid) | 1.3 X 10-5 |
| HCN (Hydrocyanic Acid) | 4.9 X 10-10 |
I posted this question before and they got the answer of 8.00g which is NOT CORRECT, so I was looking someone else to help me with this.
In: Chemistry
In my lab we found OUR average molarity to be 0.83334 M, but we used 3% H2O2 (hydrogen peroxide), so I'm not sure how to do this or what numbers to even use.
7. Convert the average molarity of hydrogen peroxide into % (wt) of hydrogen peroxide (the density of the solution = 1.009g/ml).
8. Comparing the above calculated % of hydrogen peroxide with the known (labeled on the bottle) value, calculate the % experimental error.
In: Chemistry