 # gammagirl

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• ### studiot

1. yes should if be (x +.00622)(4x^2)? Idk how the solution to that math.
2. Determine the mass in grams of lead (II) iodide that will dissolve in 500.0 mL of a solution containing 1.03 grams of lead (II) nitrate. Ksp of lead (II) iodide is 1.4 x 10-8. 1.03 g x mol = .00622 mol ------ ------ ------------- 0.5 L 331.2 L PbI2 (s) ==> PbI2(aq) ==>Pb2+ + 2I- .00622 2x^2 (.00622)(2x)^2=1.4 x 10^-8 x = 7.5 x 10^-4 M 7.5 x 10^-4 m/L x .5 L x 461.01 g/mole = .173 g
3. Absorbance of FeScn2+ And the link IS the experiment And that is the point the reaction is in equilibrium but the questions are confusing. If The Fe3+ was in excess, then Scn-=FeScn2+. But for the first question question, Fe 3+=Scn - is the same amount (as in the lab). It is something intuitive and easy.
4. 1.Consider a reaction mixture that has initial concentrations of Fe3+ = 0.0050 M and SCN– = 0.0050 M. Without doing any calculations, which of the following values do you know? a) The equilibrium concentrations of Fe3+, SCN– , and FeSCN2+ b) The sum of the equilibrium concentrations of Fe3+ , SCN– , and FeSCN2+ c) The product of the equilibrium concentrations of Fe3+ , SCN– , and FeSCN2+ d) The ratio of equilibrium concentrations of products to reactants: [FeSCN2+]/[Fe3+][SCN– ] e) The ratio of equilibrium concentrations of reactants to products: [Fe3+][SCN– ]/[FeSCN2+] Explain your answer, Earlier in the experiment, a calibration curve measuring absorbance on the y-axis and concentration on the x-axis was generated from a set of 3 standard solutions. So, I am thinking perhaps the d and e are known due to a concentration/absorbance ratio that graph? Next is this question, Consider a reaction mixture that has an initial concentration of FeSCN2+ = 0.0050 M, no Fe3+ or SCN. Without doing any measurements or calculations, which of the following two values do you know? a) The equilibrium concentrations of Fe3+, SCN– , and FeSCN2+ b) The sum of the equilibrium concentrations of Fe3+, SCN– , and FeSCN2+ c) The product of the equilibrium concentrations of Fe3+, SCN– , and FeSCN2+ d) The ratio of equilibrium concentrations of products to reactants: [FeSCN2+]/[Fe3+][SCN– ] e) The ratio of equilibrium concentrations of reactants to products: [Fe3+][SCN– ]/[FeSCN2+] Explain your answer. By the way the equation for both is , the equation is Fe3+ (aq) + HSCN (aq) <-----> FeSCN2+ (aq) and everything is 1:1. Using the ice table, Fe3+ is 0.0050M -x , SCN-, is 0.0050M- x. So, we know a and b?
5. What do you mean by slightly different noise?
6. Is the bottom line that both values are nearly perfect straight lines making the differences between the numbers negligible?
7. How is a correlation coefficient of 0.999992 better than a correlation coefficient of 0.99996 even though both analyses resulted in the same molar absorptivity for the analyte using spectrophotometric analysis? Does 0.999992 result in a higher correlation coefficient than 0.99996? If so, why?
8. I was thinking "A shoulder band usually appears on the lower wavenumber side in primary and secondary liquid amines arising from the overtone of the N–H bending band: this can confuse interpretation."
9. When obtaining an IR spectrum, a secondary amine should exhibit only one N-H stretch, however, when a student ran his sample, two N-H stretches appeared in the spectrum. What could account for this?
10. Both are good points. Thank-you
11. A secondary amine should only exhibit only one N-H stretch. However, 2 N-H stretches appeared in the spectrum. What could account for this?
12. I used 3 mL of 95% ethanol? 3mL x 0.789/ml x mol/46.068 g = 0.0513gm OR 95gm/100ml =x/3ml, x= 2.85 gm ethanol x mol/46.068 g= 0.06187 gm
13. The answers mentioned above are correct, but I thoroughly understand the experiment at a higher level. Therefore, the Henderson-Hasselbach case is closed.
14. ## Determine the solution to the following differential equation: dA/dt = -0.3A and A(2) = 400

I appreciate you.
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