Passing the hard water sample through a chemical exchanges the ions with the ion of the same charge. Identify the chemical, the ion that replaces and the type of hardness being removed.

Options

A. Permutit, `Na^+` ion, permanent hardness
B. Sodium carbonate, `Ca^(+2)` ion, temporary hardness
C. Calcium hydroxide,` Mg^(+2)` ion, temporary hardness
D. Sodium chloride, `Na^+ ion`, permanent hardness

Explanation

To solve the problem, we need to identify the chemical used for ion exchange, the ion that replaces the original ion in hard water, and the type of hardness being removed. Here’s a step-by-step solution:

### Step 1: Understand Hard Water
Hard water contains high concentrations of minerals, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions. These ions are responsible for the hardness of water.

**Hint:** Hard water is characterized by the presence of certain metal ions.

### Step 2: Identify the Chemical Used for Ion Exchange
The chemical commonly used for ion exchange to soften hard water is sodium ion exchange resin. This resin exchanges sodium ions (Na⁺) for the calcium (Ca²⁺) and magnesium (Mg²⁺) ions present in hard water.

**Hint:** Look for a chemical that can replace calcium and magnesium ions with sodium ions.

### Step 3: Identify the Ion that Replaces
In the ion exchange process, the sodium ions (Na⁺) from the resin replace the calcium (Ca²⁺) and magnesium (Mg²⁺) ions in the hard water. Therefore, the ion that replaces is sodium (Na⁺).

**Hint:** The replacement ion should have the same charge as the ions it is replacing.

### Step 4: Identify the Type of Hardness Being Removed
The hardness being removed by this process is known as "temporary hardness" or "permanent hardness," depending on whether the hardness is due to bicarbonates or sulfates/chlorides of calcium and magnesium. In this context, since we are discussing ion exchange, it typically refers to the removal of permanent hardness.

**Hint:** Consider the types of hardness: temporary hardness is due to bicarbonates, while permanent hardness is due to sulfates and chlorides.

### Final Summary
- **Chemical used:** Sodium ion exchange resin
- **Ion that replaces:** Sodium ion (Na⁺)
- **Type of hardness being removed:** Permanent hardness