Answer:
It is heterogeneous as it is made up of visibly different substances or phases.
Answer: pH = 3.15
Explanation: Solved in the attached picture.
Using AVOs number
moles -> molecules
multiply moles # by AVOs #
15 x (6.022x10^23=
The average mass of the pennies in the sample is 2.16 g.
We have a set of pennies from which 10.00% have an average mass of 2.15 g and 90.00% have an average mass of 2.156 g. The average mass (am) of the whole set is a weighted average, that considers the mass (m) and the percentage (perc) of each group. We can calculate it using the following expression.

The average mass of the pennies in the sample is 2.16 g.
You can learn more about weighted average here: brainly.com/question/18554478
The big bang; that's what most scientists think.