<span>This would be the atomic mass. In an atom of carbon-12, there are 6 protons and 6 neutrons at rest (electrons have a negligible mass and are usually not part of the overall mass calculation). All atomic masses are based off the measurements of this specific iteration of carbon.</span>
The answer is 64.907 amu.
The atomic mass of an element is the average of the atomic masses of its isotopes. The relative abundance of isotopes must be taken into consideration, therefore:
atomic mass of copper = atomic mass of isotope 1 * abundance 1 + atomic mass of isotope 2 * abundance 2
We know:
atomic mass of copper = 63.546 amu
The atomic mass of isotope 1 is: 62.939 amu
The abundance of isotope 1 is: 69.17% = 0.6917
The atomic mass of isotope 1 is: x
The abundance of isotope 2: 100% - 69.17% = 30.83% = 0.3083
Thus:
63.546 amu = 62.939 amu * 0.6917 + x * 0.3083
63.546 <span>amu = 43.535 amu + 0.3083x
</span>⇒ 63.546 amu - 43.535 amu = 0.3083x
⇒ 20.011 amu = 0.3083x
⇒ x = 20.011 amu ÷ 0.3083 = 64.907 amu
<h3>
Answer:</h3>
3.342 x 10^24 molecules of water
<h3>
Explanation:</h3>
Given;
Mass of water = 100.0 g
Required to determine the number of molecules in 100.0 g of water
Using Avogadro's constant
1 mole of a compound contains 6.022 × 10^22 molecules
Thus;
1 mole of H₂O contains 6.022 × 10^23 molecules
But;
1 mole = 18.02 g/mol
Therefore;
18.02 g of water contains 6.022 × 10^23 molecules
100.0 g of water will have;
= (100. 0 g ×6.022 × 10^23 molecules) ÷ 18.02
= 3.342 x 10^24 molecules
