The element copper has two stable isotopes, copper-63 with a mass of 62.93 amu and copper-65 with a mass of 64.93 amu. from the atomic weight of cu = 63.54 one can conclude that:

- both isotopes have the same percent natural abundance
- copper-65 has the highest percent natural abundance
- most copper atoms have an atomic mass of 63.54
- copper-63 has the highest percent natural abundance

The Cu-63 isotope has the highest percent natural abundance

Explanation:

Average atomic mass is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

We are given:

Two isotopes of Copper, which are Cu-63 and Cu-65

Average atomic mass of copper = 63.54 amu

As, the average atomic mass of copper is closer to the mass of Cu-63 isotope. This means that the relative abundance of this isotope is the highest as compared to the other isotope.

Percentage abundance of Cu-63 isotope = 69.2%

Percentage abundance of Cu-65 isotope = 30.8 %

Hence, the Cu-63 isotope has the highest percent natural abundance

false

because it does not have the potential to be entirely used up

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.