Calculate :
the weight of 0.25 g atom of calcium.

Explanation

To calculate the weight of 0.25 gram atom of calcium, follow these steps:

### Step 1: Understand the concept of gram atom
A gram atom (or mole) of an element is defined as the mass of the element in grams that is numerically equal to its atomic mass in atomic mass units (amu). For calcium, the atomic mass is approximately 40 amu.

### Step 2: Identify the atomic mass of calcium
The atomic mass of calcium (Ca) is given as 40 g/mol.

...