Chemistry Activity-pH

Answers!

#1-3. No answers required.

#4. The equation should be: =10^(-pH) where the value of the pH will be represented with a specific spreadsheet cell address.

#5. Student’s graphs may vary as well as their explanations.

#6. No answer required.

#7. The graph should not contain any loops/overlaps because each pH value has a one to one correspondence to a particular hydrogen ion concentration (H+). Two solutions cannot have the same pH but different H+ concentrations.

#8. Students should SORT their data in ascending order. This will remove the loops.

#9. The graph should look like the one below.

#10. The values at the “tail end” of the graph are all crowded at the bottom because the range of H+ concentrations is so large and the smaller values are close to zero. The values are not zero but appear to be because of the range of data and scale used on the graph.

#11. No answer required.

#12. The graph of the last four data points will have a shape very similar to the larger graph.

#13. The shape of the graph changed to a curve because the spreadsheet program automatically adjusts the scale of the graph. The range of H+ values is smaller for this graph and therefore the data points are spaced farther apart.

#14. Students should observe that as the H+ concentration increases the pH decreases because the graph on the line slopes to the right. The curved shape of the graph is significant because it tells us that the inverse relationship is exponential and not a direct proportion, which would have been linear. This is an important relationship for students to understand, as a common mistake made with pH is that students will correlate a high pH with a high number of H+ ions, which is incorrect!