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Science Question for Wednesday, July 23rd, 2014

If the trends indicated in the table were to continue, one would predict the pH of the sediments at a depth of 35 cm to be:

**A.** 1.5.

**B.** 3.5.

**C.** 4.5.

**D.** 6.0.

## Incorrect

Given that pH decreases linearly at the rate of 0.5 unit for every 0.5 cm decrease in depth, a depth of 55 cm would be required before the pH was 1.5.

## Correct!

According to the table, pH decreases linearly at the rate of 0.5 unit for every 5 cm decrease in depth.

At 20 cm, pH = 5.0; 35 cm is three 5-cm increments below 20 cm. At 35 cm, pH would be 5.0 – (3 0.5) = 5.0 – 1.5 = 3.5.

## Incorrect

Given that pH decreases linearly at the rate of 0.5 unit for every 0.5 cm decrease in depth, a depth of 25 cm—not 35 cm—would have a pH of 4.5.

## Incorrect

At a depth of 10 cm, the pH is 6. Given that pH decreases as depth increases, at a depth of 35 cm the pH would be less than 6.