Explain why the presence of crystals of the sample at the starting point causes streaking of the TLC plate during development.
In: Chemistry
Weak base/ Strong acid titration curve question.
1) In the titration of .0400 M weak base B of 50 ml with .100 M HCl. What is the solution pH before any HCl is added?
2) In the titration of .0400 M weak base B of 50 ml with .100 M HCl. What is the solution pH after 10 ml HCl is added?
3) In the titration of .0400 M weak base B of 50 ml with .100 M HCl. What is the solution pH at the equivalence point? (20 ml, at the equivalence point)
4) In the titration of .0400 M weak base B of 50 ml with .100 M HCl. What is the solution pH after 25 ml HCl is added?
*pKa of the conjugate acid of base is: 7.90
In: Chemistry
Solutions with a constant volume of 10.0 mL contain 0.750mg of
dissolved tooth enamel plus variable concentrations of added
Sr.
Added Sr(ng/mL=ppb) Signal(arbitrary units)
Added Sr: 0 , 2.50, 5.00, 7.50, 10.00
Signal: 28.0, 34.3, 42.8, 51.5, 58.6
a.) Find concentration of Sr and its uncertainty in the 10.0mL
solution in ppb.
b.) Find concentration of Sr in tooth enamel in ppm.
c.) If the standard addition intercept is the major source of
uncertainty, find the uncertainty in the concentration of Sr in
tooth enamel in ppm.
d.) Find the 95% confidence interval for Sr in tooth enamel
I figured out a: 8.72 +/- 0.43 ppb, I just don't understand the rest
In: Chemistry
A wedding ring has a mass of 7.804 grams and is made of gold and silver. When the ring has been heated to 96.53
In: Chemistry
A. The activation energy of a certain reaction is 42.0 kJ/mol . At 29 ∘C , the rate constant is 0.0190s−1. At what temperature in degrees Celsius would this reaction go twice as fast?
B. Given that the initial rate constant is 0.0190s−1 at an initial temperature of 29 ∘C , what would the rate constant be at a temperature of 120. ∘C for the same reaction described in Part A?
Please give the correct units too. Thank you!
In: Chemistry
a.You have 40.0 mL of a 0.100 M solution of HClO, with a Ka of 3.0 x 10-8. b. What is the pH of the solution after the addition of 30.0 mL of 0.200 M NaOH?
In: Chemistry
A production facility heats various equipment using a network of heated air and water vapor lines. A boiler produces a 195.0 mol/hr stream consisting of 0.590 mol fraction of water and 0.410 mol fraction of air at 131.0°C and 5200.0 mmHg. The air and water vapor cool as the gases move away from the boiler, and steam traps collect and remove condensed water from the lines while the pressure remains constant.
a) If a total of 65.6 mol/hr of condensed water is removed from the air and vapor lines, what is the composition of the air and vapor mixture leaving the steam lines?
b) Use the Antoine equation for water valid between 60°C and 150ºC to find the temperature of the air and vapor mixture leaving the heating lines.
In: Chemistry
If 1.2 g of aspirin were dissolved in 100 mL of water, how much aspirin might you be able to recover if you were to extract the aqueous solution with 100 mL of dichloromethane? Also calculate the percent recovery.
If instead of extracing the aqueous layer with 100 mL of dichloromethane, what would have been teh percent recovery if you had used two sucessive 50 mL protions of dichloromethane?
In: Chemistry
What volume (to the nearest 0.1 mL) of 7.10-M HCl must be added to 0.550 L of 0.350-M K2HPO4 to prepare a pH = 7.50 buffer?
In: Chemistry
Calculate the pH change that results when 12 mL of 2.8 M HCl is added to 580. mL of each of the following solutions. Use the Acid-Base Table. Please see pH changes - part a and b and pH changes - part c and d for assistance.
(a) pure water
(b) 0.10 M CH3COO−
(c) 0.10 M CH3COOH
(d) a solution that is 0.10 M in each CH3COO− and CH3COOH.
In: Chemistry
A 5.079 g sample of a solid, weak, monoprotic acid is used to make a 100.0 mL solution. 26.00 mL of the resulting acid solution is then titrated with 0.09454 M NaOH. The pH after the addition of 18.00 mL of the base is 5.54, and the endpoint is reached after the addition of 47.60 mL of the base. Please see Titration to Determine Molecular Weight for assistance.
(a) How many moles of acid were present in the 26.00 mL sample? mol
(b) What is the molar mass of the acid? g/mol
(c) What is the pKa of the acid?
In: Chemistry
If the Kb of a weak base is 3.2 × 10^-6, what is the pH of a 0.50 M solution of this base?
In: Chemistry
Aqueous solutions of lead(II) nitrate and potassium bromide are mixed together. (The solution turns cloudy white during the re
In: Chemistry
How was excess NaOH avoided in the separated solid soap?
In: Chemistry
calculate the pH of the following aqueous solution at 25 degreesCelsius and .35M NaF (pKa for HF=3.14)
In: Chemistry