Question

CHEM 110 Lab balt-60, a gamma emitter, is a synthetic isotope that is produced in nuclear reactors. In lab you Knowing what you learned in lab and what we discussed in lecture, predict what happens to the Co- 60 radiation cps under the following conditions. Does the cps increase, decrease, or sta A. a piece of paper is placed between the probe and the Co-60 B. a piece of gelatin is placed between the probe and the Co-60 C. your hand is placed between the probe and the Co-60 D. the probe and Co-60 are separated by a large distance e radiation counts per second (cps) of a sample of Co-60 to be approximately 1000 eps. 4. Write a chemical equation that shows how a H POs/NaH POs buffer will react to the addition of a strong acid and a chemical equation that shows what happens with the addition of a strong base. /42 In the lab you set up a titration experiment with 0.120 M NaOH in the buret. A. Sketch the set up for this experiment below B. Determine the volume (mL) of NaOH solution needed to neutralize the acid. (Hint: write and 30.0 mL of 0.100 M HP04 solution in a flask and 5. balance the equation for neutralization first.) What would happen if you forgot to add the phenothalein to your acid? C. .12 6120 c) CHEM 110 Lab Cobalt-60, a gamma emitter, is a synthetic isotope that is produced in nuclear reactors. In lab you measured the radiation counts per second (cps) of a sample of Co-60 to be approximately 1000 cps. Knowing what you learned in lab and what we discussed in lecture, predict what happens to the Co- 60 radiation cps under the following conditions. Does the cps increase, decrease, or stay the same? A. a piece of paper is placed between the probe and the Co-60 B. a piece of gelatin is placed between the probe and the Co-60 C. your hand is placed between the probe and the Co-60 D. the probe and Co-60 are separated by a large distance 4. Write a chemical equation that shows how a HsPO4/NaH2PO, buffer will react to the addition of a strong acid and a chemical equation that shows what happens with the addition of a strong base. Inthe labyou set up a titration experiment with 30.0 mL of 0.1 00 M ΗΡΟ. solution in a flask and 5 0.120 M NaOH in the buret. A. Sketch the set up for this experiment below B. Determine the volume (mL) of NaOH solution needed to neutralize the acid. (Hint: write and balance the equation for neutralization first.) What would happen if you forgot to add the phenothalein to your acid? C. 25.0 mL 61205

Answer 1

3. The following thing is placed between the probe and Co-

A) a piece of paper: stays the same.

B) gelatin: decreases

C) human hand: stays the same

D) large distance: stays the same.

4. Buffer solution: H₃PO₄+NaH₂PO₄

Addition of strong acid (HCl):

NaH₂PO₄+HCl-> H₃PO₄+Na⁺+Cl^-

Addition of strong base (NaOH):

H₃PO₄+NaOH->NaH₂PO₄+H₂O

5. Using V_acidS_acid=V_baseS_base, one can determine the volume of base and it is given as

30*0.1/0.12 ml=25 ml.

Phenolphthalein acts as indicator by changing the color from colorless (acidic) to pink ( basic). Therefore, endpoint cannot be detected exactly.