Which statement is incorrect?
select one:

a. the volume of solution in the buret should be recorded when the endpoint is reached.
b. it is good practice to place the flask over a white background to better observe the color change of the solution.
c. the endpoint is when the indicator changes color.
d. phenolphthalein will go from a colorless solution to a pink solution for the addition of naoh to an acid solution.
e. when the indicator changes color and remains, 2 more drops of the solution in the buret should be added.

e. When the indicator changes color and remains, 2 more drops of the solution in the buret should be added.

Explanation:

Which statement is incorrect?

Select one:

a. The volume of solution in the buret should be recorded when the endpoint is reached. CORRECT. At the endpoint, the titrant is expected to have completely reacted with the titrand.

b. It is good practice to place the flask over a white background to better observe the color change of the solution.  CORRECT. Using a white background makes it easier to detect the changes in the color of the indicator.

c. The endpoint is when the indicator changes color. CORRECT. This is the function of an indicator.

d. Phenolphthalein will go from a colorless solution to a pink solution for the addition of NaOH to an acid solution.  CORRECT. Phenolphthalein is colorless when pH < 8.3 and it is pink when pH > 10.0.

e. When the indicator changes color and remains, 2 more drops of the solution in the buret should be added. INCORRECT. When the endpoint is reached, no more titrant should be added.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms