The weights of all elements are always compared to the Carbon-12 because the mass of carbon is 12 which is the exactly the sum of protons and neutrons.

Oxygen was also considered the standard for some time but later this stander was rejected because in natural O¹⁷ and O¹⁸ were also present and this create the two different atomic mass tables.

AMU:

Atomic mass unit is define as the 1/12 the mass of an atom of carbon-12.

C12 has six neutron and six protons in the nucleus.

This unit is used to express the masses of atoms. We know that masses of atoms are very small and we do not have any such type of balance that can measure very small quantity. So that is way we use this scale to measure small quantity. For example, according to this scale

relative atomic mass of hydrogen is 1.008 amu

relative atomic mass of oxygen is 15.999 amu

relative atomic mass of uranium is 238.0289 amu

relative atomic mass of chlorine is 35.453 amu

7 0

3 years ago

Determine the overall energy change for the reaction between hydrogen and oxygen shown in Question 13. Use Figure 2.

zimovet [89]

Answer:

–500KJ

Explanation:

Data obtained from the question include the following:

Heat of reactant (Hr) = 800KJ

Heat of product (Hp) = 300KJ

Enthalphy change (ΔH) =..?

The enthalphy change is simply defined as the difference between the heat of product and the heat of reactant i.e

Enthalphy change = Heat of product – Heat of reactant

ΔH = Hp – Hr

With the above formula, we can easily calculate the enthalphy change as follow

ΔH = Hp – Hr

ΔH = 300 – 800

ΔH = –500KJ.

Therefore, the overall energy change for the reaction between hydrogen and oxygen shown in the diagram above is –500KJ

5 0

3 years ago