Question

Examine the equation below:
_NaCI + _CaF2 → _NaF + _CaCI2
To adhere to the law of conservation of mass, which set of coefficients must this equation have, in sequence from left to right?

Answer 1

To balance the equation \( \text{NaCl} + \text{CaF}_2 \rightarrow \text{NaF} + \text{CaCl}_2 \), we need to ensure that the number of each type of atom on the reactant side is equal to the number on the product side.

Let's break it down:

- On the left side (reactants):
- Sodium (Na): 1 (from NaCl)
- Chlorine (Cl): 1 (from NaCl)
- Calcium (Ca): 1 (from CaF2)
- Fluorine (F): 2 (from CaF2)

- On the right side (products):
- Sodium (Na): 1 (from NaF)
- Fluorine (F): 1 (from NaF)
- Calcium (Ca): 1 (from CaCl2)
- Chlorine (Cl): 2 (from CaCl2)

Now we can start balancing:

1. **Balance Sodium (Na)**:
- Both sides have 1 Na, so Na is balanced.

2. **Balance Calcium (Ca)**:
- Both sides have 1 Ca, so Ca is balanced.

3. **Balance Chlorine (Cl)**:
- Left has 1 Cl, right has 2 Cl. We can place a coefficient of 2 in front of NaCl:
\[
2 \text{NaCl} + \text{CaF}_2 \rightarrow \text{NaF} + \text{CaCl}_2
\]

4. **Re-evaluate Sodium (Na) and Fluorine (F)**:
- Now, we have 2 Na on the left (from 2 NaCl), and we need 2 NaF to balance:
\[
2 \text{NaCl} + \text{CaF}_2 \rightarrow 2 \text{NaF} + \text{CaCl}_2
\]

5. **Balance Fluorine (F)**:
- On the left, we still have 2 F in \( \text{CaF}_2 \), and now we added 2 NaF on the right, which gives us 2 F, so F is now balanced as well.

The final balanced equation is:
\[
2 \text{NaCl} + 1 \text{CaF}_2 \rightarrow 2 \text{NaF} + 1 \text{CaCl}_2
\]

Thus, the coefficients in sequence from left to right are:
**2, 1, 2, 1**.