Question

PLS HELPPPPPPP and explain how to do it

Answer 1

Answer: A

Explanation: When using dimensional analysis, always put similar unit-ed numbers diagnolly from each other so they 'cross out'

For example, If you had 1 mol of gold and you wanted to convert it to grams using gold's molar mass, 196.97 g/mol, it would look like this:

Start with the given number over nothing:

$\frac{1 mol Au}{} *\frac{ }{ }$

Then add your conversion, in this case the molar mass, with the MOLES on the BOTTOM, so they are diagnol with the 1 mol of Au

$\frac{1 mol Au}{ } *\frac{196.7 g Au}{1 mol}$

Always have the top right in your dimensional analysis be in the units that you are solving for. In this case, we went from moles to grams, so grams is in the top right.

Hope this helps!

Also, 6.02 x 10²³ is otherwise known as avogadros number- it is used when you are converting something from moles to molecules (or particles). For example, if instead we were going from moles of gold to molecules of gold, our dimensional analysis would look like this:

$\frac{1 mol Au}{ } *\frac{6.02 x 10^2^3 molecules Au}{1 mol}$

Answer 2

Answer: 3.613x10^24

Explanation: Avogadro’s number represents the number of atoms in one mole of substance: 6.022x10^23 atoms/mole. Multiplying the number of moles by this number reveals that, in this sample, 3.613x10^24 atoms of methane are present.