It defines the element. If you change the protons, you change the type of element. A proton is positively charged and is most of the mass of the atom, next to the neutron. Neutrons have a very very very slightly higher mass.

4 0

3 years ago

Fictitious element X has an a average atomic mass of 254.9 and only 2 isotopes, One of its isotopes has an abundance of 72.00 an

elena-14-01-66 [18.8K]

Answer:

265.2amu

Explanation:

Given parameters:

Atomic mass = 254.9amu

Abundance of isotope 1 = 72%

Atomic mass of isotope 1 = 250.9amu

Abundance of isotope 2 = 100 - 72 = 28%

Unknown:

Atomic mass of isotope 2 = ?

Solution:

To find the atomic mass of isotope 2, use the expression below:

Atomic mass = (abundance of isotope 1 x atomic mass of isotope 1) + (abundance of isotope 2 x atomic mass of isotope 2)

Now insert the parameters and find the unknown;

254.9 = (0.72 x 250.9) + (0.28 x Atomic mass of isotope 2)

254.9 = 180.648 + 0.28x atomic mass of isotope 2

254.9 - 180.648 = 0.28x atomic mass of isotope 2

74.25 = 0.28 x atomic mass of isotope 2

Atomic mass of isotope 2 = 265.2amu

8 0

3 years ago

What is the molecular formula of a hydrocarbon with m+ = 78?

fiasKO [112]

A molecular formula represents the exact number of atoms present for each element in the compound.

For carbon atom: $\frac{78}{12}$ = $6\frac{6}{12}$ ( as molar mass of carbon is 12 g/mol)

Now, 6 carbon atoms are present and rest are hydrogen atoms i.e. 6

Thus, formula becomes $C_{6}H_{6}$ ( $C_{x}H_{y})$

Now, check for unsaturation:

Degree of unsaturation = $\frac{2x+2-y}{2}$

Substitute the value of x and y,

Degree of unsaturation = $\frac{2(6)+2-6}{2}$

= $\frac{12-4}{2}$

= $4$ implies one ring and three double bonds.

Thus, formula comes out to be $C_{6}H_{6}$ i.e. benzene ring.

4 0

3 years ago