Question

'How many atoms are in 2.45 moles of copper?


2.46 × 1023 atoms

2.45 atoms

155.70 atoms

1.48 × 1024 atoms

Answer 1

Answer:

$\boxed {\boxed {\sf 1.48 \times 10^{24} \ atoms \ Cu}}$

Explanation:

We are asked to find how many atoms are in 2.45 moles of copper (Cu).

We can convert moles to atoms using Avogadro's Number or 6.022 × 10²³. This is the number of particles (atoms, molecules, formula units, etc.) in 1 mole of a substance. In this case, the particles are atoms of copper. There are 6.022 × 10²³ atoms of copper in 1 mole of copper.

We will convert using dimensional analysis, so we must set up a ratio using Avogadro's Number.

$\frac {6.022 \times 10^{23}\ atoms \ Cu}{ 1 \ mol \ Cu}$

We are converting 2.45 moles of copper to atoms, so we multiply the ratio by this value.

$2.45 \ mol \ Cu*\frac {6.022 \times 10^{23}\ atoms \ Cu}{ 1 \ mol \ Cu}$

The units of moles of copper cancel.

$2.45*\frac {6.022 \times 10^{23}\ atoms \ Cu}{ 1}$

The denominator of 1 is the same as the numerator by itself, so it can be ignored.

$2.45* {6.022 \times 10^{23}\ atoms \ Cu}$

$1.47539 \times 10^{24} \ atoms \ Cu$

The original measurement of moles (2.45) has 3 significant figures, so our answer must have the same. For the number we found that is the hundredth place. The 5 in the thousandth place to the right tells us to round the 7 up to an 8.

$1.48 \times 10^{24} \ atoms \ Cu$

There are approximately 1.48 × 10²⁴ atoms of copper in 1 mole of copper.

Answer 2

Answer:

$:\implies \rm Moles =\dfrac{No. \: of \: atoms}{Avogadro's \: number}$

$:\implies \rm M =\dfrac{N}{N_A}$

$:\implies \rm N=M \times N_A$

$:\implies \rm N=2.45\times6.022 \times {10}^{23}$

$:\implies \rm N=14.7539\times {10}^{23}$

$:\implies \rm N=1.47539\times 10^1\times {10}^{23}$

$:\implies\textsf{ \textbf{N = 1.48 \times {10} ^{24} }}$