In the lab, a 156 g sample of unknown compound KClOx was completely decomposed to produce 50.4 L of O2 (g) at STP and an unknown amount of KCl. What is the value of X

2

Explanation:

Step 1: Write the generic decomposition reaction

KClOₓ ⇒ KCl + O₂

Step 2: Calculate the moles of O₂

At STP, 1 mole of an ideal gas occupies 22.4 L.

50.4 L × 1 mol/22.4 L = 2.25 mol

Step 3: Calculate the mass corresponding to 2.25 moles of O₂

The molar mass of O₂ is 32.00 g/mol.

2.25 mol × 32.00 g/mol = 72 g

Step 4: Determine the value of x

Every 156 g of KClOₓ there are 72 g of oxygen. The mass percent of O is:

%O: 72 g/156 g × 100% = 46.2%

In KClO, the mass percent of O is: 32.00 g/90.5 g × 100% = 35.4%

In KClO₂, the mass percent of O is: 64.00 g/138.5 g × 100% = 46.2%

Then, x = 2