Because they have different boiling points
Answer:
It's the bottom layer.
Explanation:
Scientists use the Law of Superposition to determine the relative age of a layer of sedimentary rock:
The oldest rock layer is at the bottom of an undisturbed bed.
Thus, Layer A in the figure below was deposited first.
Answer:
0.00782 mol Pb
Explanation:
There are always 6.02 × 10²³ atoms in 1 mole of an element.
4.71 × 10²¹ atoms Pb × (1 mol Pb ÷ 6.02 × 10²³ atoms) = 0.00782 mol Pb