Formula Unit Mass of ZnCl2

The formula unit mass is the sum of the atomic masses of all the atoms in a formula unit of a compound. To calculate the formula unit mass of ZnCl2, we need to know the atomic masses of zinc (Zn) and chlorine (Cl).

Atomic Masses:
- The atomic mass of zinc (Zn) is 65.38 atomic mass units (u).
- The atomic mass of chlorine (Cl) is 35.45 atomic mass units (u).

Calculating the Formula Unit Mass:
To calculate the formula unit mass of ZnCl2, we need to determine the number of atoms of each element in the formula. In this case, ZnCl2 consists of one zinc atom (Zn) and two chlorine atoms (Cl).

Step 1: Determine the number of atoms of each element in the formula.
- Zn: 1 atom
- Cl: 2 atoms

Step 2: Calculate the total mass of each element.
- Zn: 1 * 65.38 u = 65.38 u
- Cl: 2 * 35.45 u = 70.9 u

Step 3: Add up the total masses of all the elements.
- Total mass = 65.38 u + 70.9 u = 136.28 u

Therefore, the formula unit mass of ZnCl2 is 136.28 atomic mass units (u).

Correct Answer:
The correct answer is option 'B' (137 u).

Explanation:
The correct answer is 137 u, which is the closest value to the calculated formula unit mass of 136.28 u. The slight difference between the calculated value and the given options could be due to rounding off the atomic masses. It is important to note that atomic masses can vary slightly depending on the isotopic composition of the element.