Question

If the table of atomic masses were established with the oxygen atom and assigned value of 100, the mass of carbon atom would be, approximately:
A.$24$
B.$75$
C.$50$
D.$112$

Answer 1

Hint:To solve the above numerical we should use the current system of atomic masses. We should be able to know the current mass of a given atom, so that we can use them to solve the given numerical and find correct values.
Formula Used:
$${\displaystyle \frac{\text{current atomic mass of first element}}{\text{The Current Atomic Mass Of Second Element}}}={\displaystyle \frac{\text{New Atomic Mass Of First Element}}{\text{New Atomic Mass Of Second Element}}}$$

Complete step by step answer:
To solve the above numerical we should find out the atoms it is saying about.
If we say here two atoms that are Oxygen and Carbon atoms are mentioned.
The current atomic mass of oxygen is = $16$ and for carbon is = $12$
Now it’s (question) saying that atomic mass of oxygen is changed or assigned as $100$.
To find carbon approximate atomic mass the following equation needs to be solved.
That is:
$${\displaystyle \frac{\text{current atomic mass of first element}}{\text{The Current Atomic Mass Of Second Element}}}={\displaystyle \frac{\text{New Atomic Mass Of First Element}}{\text{New Atomic Mass Of Second Element}}}$$
$${\displaystyle \frac{12}{16}}=$$ $${\displaystyle \frac{\text{New Atomic Mass Carbon}}{100}}$$
$$12\times {\displaystyle \frac{100}{16}}=$$New atomic mass of carbon
New atomic mass of carbon= $75$.
So, the correct option is B that is $75$.

Additional Information:
Atomic mass also refers to atomic weight which is average of all isotopes (it is one of two or more species of atoms of that chemical element which has different atomic mass) of that particular element, in which mass of every isotope is multiplied by abundance of that isotope.
To calculate the atomic mass, the sum of the number of protons and neutrons is taken which are present in the nucleus. The unit of atomic mass is $amu$(Daltons). For example:
Carbon has $12$ $amu$ atomic mass whereas Hydrogen has one $amu$ atomic mass.
Oxygen is a chemical element with atomic number of $8$. It is highly reactive non-metal and also an oxidizing agent. It belongs to period $2$ and p-block. It is from a group of chalcogens (group $16$).
Carbon is a chemical element with atomic number of $6$ .It is non-metallic and tetravalent (means $4$ electrons are free to form covalent bonds). It belongs to period $2$ and p-block. It is from a group of carbon (group $14$).

Note:
Remember the key point to solve a numerical for atomic masses is know the atomic mass of the given elements. Basic elements whose atomic mass we should always remember are
Carbon $$\left(12\right)$$
Oxygen $\left(16\right)$
Hydrogen$\left(1\right)$
Nitrogen $$\left(14\right)$$
Chlorine$$\left(35.5\right)$$