Mitosis starts and ends with
diploid cells. That means they
have two sets of chromosomes
(both parents each contribute a
set). In humans, how many
chromosomes should be in each
of these diploid cells after
mitosis?

There should be 23 pairs of chromosomes in each diploid cell of humans after mitosis.

A typical vegetative cell of humans is a diploid (2n) with 23 pairs of chromosomes. in other words, for vegetative cells of humans:

        2n = 23 chromososomes

During meiosis, the number of chromosomes is halved to produce haploid gametes or sex cells. During fertilization, a haploid male gamete (n = 23) fuses with a haploid female gamete (n= 23) to produce a diploid (2n = 23) zygote.

During mitosis, however, a diploid cell divides to give rise to 2 diploid daughter cells.

More on diploid and haploid cells can be found here: link

46 chromosomes

Explanation:

Each diploid cell has two sets of chromosomes (i.e 2n) and are 46 in total. After undergoing mitosis, each of these cells divides into two daughter cells with the exact chromosome number as the parent cell.

Thus, mitosis occurs only in somatic (body) cells and yield daughter cells with 46 chromosomes.