Answer:
[tex]\boxed {\boxed {\sf 2.29 *10^{24} \ atoms \ Ca}}[/tex]
Explanation:
To convert from moles to atoms, we must use Avogadro's Number.
[tex]6.022*10^{23}[/tex]
This number tells us the number of particles (atoms, molecules, ions, etc.) in 1 mole. In this case, the particles are atoms of calcium (Ca).
[tex]6.022*10^{23} \ atoms \ Ca / 1 \ mol \ Ca[/tex]
1. Convert from moles to atoms.
Write Avogadro's number as a fraction.
[tex]\frac {6.022 *10^{23} \ atoms \ Ca} {1 \ mol \ Ca}[/tex]
Multiply the given number of moles of calcium (3.8) by the fraction created.
[tex]3.8 \ mol \ Ca *\frac {6.022 *10^{23} \ atoms \ Ca} {1 \ mol \ Ca}[/tex]
The moles of calcium will cancel.
[tex]3.8 *\frac {6.022 *10^{23} \ atoms \ Ca} {1 }[/tex]
The denominator of 1 is insignifcant and we can turn this into a simple multiplication problem.
[tex]3.8 * {6.022 *10^{23} \ atoms \ Ca}[/tex]
[tex]2.28836*10^{24} \ atoms \ Ca[/tex]
2. Round
The problem tells us to round to 2 decimal places or the hundredth place.
[tex]2.28836*10^{24} \ atoms \ Ca[/tex]
The 8 in the thousandth place tells us to round the 8 to a 9.
[tex]2.29 *10^{24} \ atoms \ Ca[/tex]
There are about 2.29*10²⁴ atoms of calcium in 3.8 moles.
