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

`:\implies \rm Moles =(No. \: of \: atoms)/(Avogadro's \: number) \\`

`:\implies \rm M =(N)/(N_A) \\`

`:\implies \rm N=M * N_A \\`

`:\implies \rm N=2.45*6.022 * {10}^(23) \\`

`:\implies \rm N=14.7539* {10}^(23) \\`

`:\implies \rm N=1.47539* 10^1* {10}^(23) \\`

`:\implies\textsf{ \textbf{N = 1.48$*${10}$^(24)$}} \\`

Answer 2

`\boxed {\boxed {\sf 1.48 * 10^(24) \ atoms \ Cu}}`

Step-by-step 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 * 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 * 10^(23)\ atoms \ Cu}{ 1 \ mol \ Cu}`

The units of moles of copper cancel.

`2.45*\frac {6.022 * 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 * 10^(23)\ atoms \ Cu}`

`1.47539 * 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 * 10^(24) \ atoms \ Cu`

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