Ch. 19 Lab Applications Review

If a solution turns Blue Litmus paper red, what type of solution is it?

• acidic

• basic

• neutral

Answer explanation

Litmus paper turns (or stays) red in acids.

If a solution turns Red Litmus paper blue, what type of solution is it?

• acidic

• basic

• neutral

Answer explanation

Litmus paper turns (or stays) red in acids.

A neutral solution will always change the color of Red or Blue Litmus paper.

• True

• False

Answer explanation

Usually Litmus paper may not change with a neutral solution so it's best to also test with pH paper.

Stopping a titration at the first sign of pink will make the calculated molarity:

• too low

• too high

• that doesn't matter

Answer explanation

Stopping at the first sign of pink does not allow for enough base to be added. This makes the calculated molarity of the acid lower than the true value.

If a titration is stopped only when the contents turn dark pink, how will that affect the calculated molarity?

• too low

• too high

• that doesn't matter

Answer explanation

Going to a dark pink color during a titration means that too much base was used. This makes the calculated molarity of the acid higher than the true value.

Which of the following is the most accurate way to determine the acidity of a solution?

• pH indicator paper

• pH meter

• indicator solution added during a titration

Answer explanation

A pH meter will give a reading to 1 or 2 decimals of accuracy, better than trying to decipher a color.

The following data was collected with indicator papers:

Red Litmus: RED

Blue Litmus: BLUE

pH Paper: yellowish-green; 6

What type of solution is it?

• acidic

• basic

• neutral

Answer explanation

This would be a weak acid because the pH was 6, even though the Litmus papers didn't change.

The following data was collected with indicator papers:

Red Litmus: RED

Blue Litmus: pinkish/purple

pH Paper: orangish-yellow; 4

What type of solution is it?

• acidic

• basic

• neutral

Answer explanation

All data points to an acidic solution.

The following data was collected with indicator papers:

Red Litmus: purple

Blue Litmus: blue

pH Paper: dark blue; 12

What type of solution is it?

• acidic

• basic

• neutral

Answer explanation

All data points to a basic solution.