Two important ores of metals are given below
Malachite `CuCO_(3).Cu(OH)_(2).xH_(2)O`
Carnallite `KCl.MgCl_(2).yH_(2)O`
What is y-x?

Answer

To solve the problem, we need to determine the values of \( x \) and \( y \) from the given chemical formulas of the ores Malachite and Carnallite.

### Step 1: Analyze the formula of Malachite
The formula for Malachite is given as:
\[ \text{CuCO}_3 \cdot \text{Cu(OH)}_2 \cdot x \text{H}_2\text{O} \]
In this formula, \( x \) represents the number of water molecules associated with Malachite.

### Step 2: Determine the value of \( x \)
It is mentioned in the video that Malachite does not contain any water of crystallization. Therefore, we can conclude:
\[ x = 0 \]

### Step 3: Analyze the formula of Carnallite
The formula for Carnallite is given as:
\[ \text{KCl} \cdot \text{MgCl}_2 \cdot y \text{H}_2\text{O} \]
In this formula, \( y \) represents the number of water molecules associated with Carnallite.

### Step 4: Determine the value of \( y \)
The video states that the formula for Carnallite includes 6 water molecules. Thus, we have:
\[ y = 6 \]

### Step 5: Calculate \( y - x \)
Now that we have both values:
- \( x = 0 \)
- \( y = 6 \)

We can calculate \( y - x \):
\[ y - x = 6 - 0 = 6 \]

### Final Answer
The value of \( y - x \) is:
\[ \boxed{6} \]