A cylinder contains 68 g of ammonia at STP.
How many molecules of ammonia are present in the cylinder?

Explanation

To find the number of molecules of ammonia (NH₃) present in a cylinder containing 68 g of ammonia at STP, we can follow these steps:

### Step 1: Determine the molar mass of ammonia (NH₃)
The molar mass of ammonia can be calculated by adding the atomic masses of its constituent elements:
- Nitrogen (N) has an atomic mass of approximately 14 g/mol.
- Hydrogen (H) has an atomic mass of approximately 1 g/mol, and since there are three hydrogen atoms in ammonia, we multiply by 3.

**Calculation:**
...