Calcium carbide reacts with nitrogen and forms an important fertiliser, calcium cynamide. How much calcium cynamide is formed when `6.4 g` of calcium carbide is completely converted into cyanamide?

Explanation

To solve the problem of how much calcium cyanamide (CaCN₂) is formed when 6.4 g of calcium carbide (CaC₂) reacts with nitrogen, we can follow these steps:

### Step 1: Write the balanced chemical equation
The reaction between calcium carbide and nitrogen can be represented as:
\[ \text{CaC}_2 + \text{N}_2 \rightarrow \text{CaCN}_2 + \text{C} \]

### Step 2: Calculate the molar mass of calcium carbide (CaC₂)
- The molar mass of calcium (Ca) = 40 g/mol
- The molar mass of carbon (C) = 12 g/mol
- Therefore, the molar mass of CaC₂:
\[ \text{Molar mass of CaC}_2 = 40 + (2 \times 12) = 40 + 24 = 64 \text{ g/mol} \]

### Step 3: Calculate the molar mass of calcium cyanamide (CaCN₂)
- The molar mass of nitrogen (N) = 14 g/mol
- Therefore, the molar mass of CaCN₂:
\[ \text{Molar mass of CaCN}_2 = 40 + (1 \times 14) + (1 \times 12) = 40 + 14 + 12 = 66 \text{ g/mol} \]

### Step 4: Determine the amount of calcium cyanamide produced
From the balanced equation, we can see that 1 mole of CaC₂ produces 1 mole of CaCN₂.

### Step 5: Calculate the moles of calcium carbide used
Using the mass of calcium carbide:
\[ \text{Moles of CaC}_2 = \frac{\text{mass}}{\text{molar mass}} = \frac{6.4 \text{ g}}{64 \text{ g/mol}} = 0.1 \text{ mol} \]

### Step 6: Calculate the moles of calcium cyanamide produced
Since the molar ratio of CaC₂ to CaCN₂ is 1:1, the moles of CaCN₂ produced will also be 0.1 mol.

### Step 7: Calculate the mass of calcium cyanamide produced
Using the moles of calcium cyanamide:
\[ \text{Mass of CaCN}_2 = \text{moles} \times \text{molar mass} = 0.1 \text{ mol} \times 66 \text{ g/mol} = 6.6 \text{ g} \]

### Final Answer
The amount of calcium cyanamide formed is **6.6 g**.

---