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Number of results: 11

ChemB
How do you know what number goes on the top and bottom for the disintegration?
Monday, January 23, 2012 at 12:49am by L.Bianchessi

ChemB
Just calculate the mols (or the molarity of each) and plug into the Henderson-Hasselbalch equation.
Monday, March 12, 2012 at 2:59am by DrBob222

ChemB
Oh, okay. Do I always use that equation for any order rxn involving time? How about the units, would it be yrs^-1 or just years?
Monday, January 23, 2012 at 12:49am by L.Bianchessi

ChemB
k = 0.693/t1/2 Then ln(No/N) = kt No = 100 N = 79.5 k from above solve for t in years.
Sunday, January 22, 2012 at 9:28pm by DrBob222

ChemB
CALCULATE PH OF THE SOLUTION THAT RESULTS FROM EACH SOLUTION A) 150.0mL OF 0.25M HF WITH 225.0 mL OF 0.30M NaF Help please, these buffer questions are confusing.
Monday, March 12, 2012 at 2:59am by ALISON

ChemB
A forming acid solution has a pH of 3.25. Which of these substances will raise the pH of the solution upon addition? Explain. A) HCl B) NaBr C) NaCHO2 D) KCl
Monday, March 12, 2012 at 2:12am by ALISON

ChemB
I don't agree with your value for k. k = 0.693/t1/2 = 0.0001209 Yr^-1 If we can detect 0.1 dpm, then ln(15.3/0.1) = kt and solve for t. The web states that 58,000 to 62,000 years can be reliable determined by rediocarbon dating. This is in that ball park.
Monday, January 23, 2012 at 12:49am by DrBob222

ChemB
measurements of carbon 14 taken from linen wrappings of the book of isaiah from the dead sea scrolls indicate that the scrolls contain 79.5% of the carbon 14 expected in living tissue. how old are these scrolls if the half life of carbon 14 is 5730 years? All radioactive decay...
Sunday, January 22, 2012 at 9:28pm by L.Bianchessi

ChemB
Did you mean "formic" acid? Adding HCl will LOWER (make it more acid). Adding NaBr or KCl can't have any effect since these are salts of strong acid and strong bases. That leaves only one. I assume NaCHO2 is sodium formate which is a base and that will raise the pH (make it ...
Monday, March 12, 2012 at 2:12am by DrBob222

ChemB
No. ln(No/N) = kt is good only for first order AND in it's complete form is ln(No/N) = akt. No = number of atoms initially N = number of atoms at time t. Note: usually number; however, dpm, concn, or other initial/final states work as well. In this case I used 15.3 for No ...
Monday, January 23, 2012 at 12:49am by DrBob222

ChemB
The activity of carbon 14 in living tissue is 15.3 disintegrations per minute per gram of carbon. The limit for reliable determination of age is based on carbon 14 is .10 disintegration per min per gram of carbon. Calculate the max age of a sample that can be dated accurately ...
Monday, January 23, 2012 at 12:49am by L.Bianchessi

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