Answer:
Uracil
Explanation:
The base that will NOT combine with 2-deoxyribose to form a nucleic acid is Uracil.
2-deoxyribose is a pentose sugar found in the DNA (Deoxyribonucleic acid). It is devoid of oxygen in its 2' position. The bases found in DNA are Adenine, Guanine, Cytosine and Thymine. Adenine, Guanine, and Cytosine are also found in RNA (Ribonucleic acid). Thymine is not present in RNA, it is only found in DNA. The base found in RNA is Uracil which in turn is not present in DNA. The five carbon sugar present in RNA is ribose which combines with Uracil.
Answer:
Considering the half-life of 10,000 years, after 20,000 years we will have a fourth of the remaining amount.
Explanation:
The half-time is the time a radioisotope takes to decay and lose half of its mass. Therefore, we can make the following scheme to know the amount remaining after a period of time:
Time_________________ Amount
t=0_____________________x
t=10,000 years____________x/2
t=20,000 years___________x/4
During the first 10,000 years the radioisotope lost half of its mass. After 10,000 years more (which means 2 half-lives), the remaining amount also lost half of its mass. Therefore, after 20,000 years, the we will have a fourth of the initial amount.
<span>Avogadro's number
represents the number of units in one mole of any substance. This has the value
of 6.022 x 10^23 units / mole. This number can be used to convert the number of
atoms or molecules into number of moles.
163 g Ca (1 mol / 40.08 g) ( </span>6.022 x 10^23 atoms / 1 mol ) = 2.45 x10^24 atoms Ca
