4. A1.00 L buffer is made containing 50.0 mmol of bromoacetic acid (pKa 290 and

Question

4. A1.00 L buffer is made containing 50.0 mmol of bromoacetic acid (pKa 290 and 75.0 mmol of sodium bromoacetate. What volume of 2.00 M NaOH must be added to increase the pH ofthis buffer to 4.00? 5. How does a photomultiplier tube detect fluorescence from a sample? 6. X and Y are two compounds that absorb infrared radiation. The transmittance ofo.0100Mx and 0,0100 MY were obtained in a 0.00500 cm cell and are listed on the following page (measured at the wavenumber of maximum ab mum transmittance for each compound, respectively). A mixture of A and B in a 0.00500 cm cell had a transmittance of 34.0% at 2022 cm 1 and 38.3 at 1993 cm 1. What are the concentrations ofx and Y in the mixture? Wavenumber (cm Pure A Pure B 31.0 T 97.4 T 2022 79.7% T 20.0% T 1993 7 The calcium content of a person's urine was determined on two different days. Are the average values significantly different at the 95% level? Number of [Cal (mg/L) measurements Day 235 at 9 251 8

Explanation / Answer

X 1=235

X2=251

| X 1- X 2| =t S pooled / sqrt of N2N2/ N1+N2

S pooled / sqrt of N2N2/ N1+N2

S pooled = sqrt of {      [9^2*(6-1)+ 8^2*(4-1)] / (6+4 -2) }

=sqrt of { [81*(5)+ 64*(3)] / 8 }

= sqrt of ( 597/8)=8.63 mg/l

T= = X 1- X 2| sqrt of( N2N2/ N1+N2) / S pooled

= (X 1- X 2| sqrt of( N2N2/ N1+N2) / S pooled

= (16| sqrt of( 24/ 100) / 8.63

=7.83// 8.63=0.907

T ABLE VALUE AT 95% =2.36

IT DIFFERENT AT 95% CONFIDENCE LEVEL

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