Question

Carlos is making phosphorus trichloride using the equation below.

2P +3Cl2 _PCl3

What coefficient of PCl3 would show that the law of the conservation of mass is represented in the chemical equation?

4
3
2
1

Answer 1

To indicate that the law of conservation of mass is represented in the chemical equation, we need to balance the number of atoms of each element on both sides of the equation.

The given equation is:

\[ 2P + 3Cl_2 \rightarrow \text{PCl}_3 \]

Let's analyze this equation:

- On the left side, we have:
- 2 phosphorus (P) atoms
- 6 chlorine (Cl) atoms (because \(3Cl_2\) means 3 molecules of \(Cl_2\), each containing 2 Cl atoms)

- On the right side (if we consider the coefficient of PCl3 as \(x\)):
- \(x\) phosphorus atoms
- \(3x\) chlorine atoms (since each \(PCl_3\) contains 3 Cl atoms)

To balance the equation, we need to ensure that the number of atoms of each element is the same on both sides.

1. For phosphorus (P):
- Left: 2
- Right: \(x\)

Setting \(x = 2\) balances phosphorus:

\[ P : 2P \text{ (left) } = 2P \text{ (right with } 2PCl_3) \]

2. For chlorine (Cl):
- Left: 6
- Right: \(3x\)

If \(x = 2\), then \(3x = 6\) which also balances chlorine:

\[ Cl : 6Cl \text{ (left) } = 6Cl \text{ (right with } 2PCl_3) \]

Thus, the balanced equation would be:

\[ 2P + 3Cl_2 \rightarrow 2PCl_3 \]

Therefore, the coefficient of PCl3 that shows conservation of mass is **2**.