The degree of hardness of a given sample of hard water is `40 p p m`. If the entire hardness is due to `MgSO_(4)`, how much of `MgSO_(4)` is present per `kg` of water?

Explanation

To find the amount of magnesium sulfate (MgSO₄) present per kg of water when the hardness is given as 40 parts per million (ppm), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Parts Per Million (ppm)**:
- The term "parts per million" (ppm) means that in 1 million parts of a solution, there are a certain number of parts of the solute. In this case, it means that in 1 million grams of water, there are 40 grams of MgSO₄.

2. **Convert ppm to grams**:
...