a 200 mL aqueous solution of ammonia has a concentration of 1.50 M. What mass of ammonia is dissolved in the solution?

Answer: To calculate the mass of ammonia dissolved in the solution, we follow these steps:

Step 1: Understand the concentration term, molarity (M), which is defined as the number of moles of solute per liter of solution.

Step 2: Given that the concentration is 1.50 M, this means we have 1.50 moles of ammonia per liter of solution.

Step 3: However, we have only 200 mL (or 0.200 L) of the solution, so we need to find out how many moles of ammonia that represents.

Use the formula: molarity (M) = moles of solute / volume of solution in liters

Rearrange the formula to solve for moles of solute: moles of solute = molarity (M) × volume of solution in liters

Step 4: Calculate the moles of ammonia in our solution: moles of ammonia = 1.50 M × 0.200 L = 0.300 moles

Step 5: To find the mass, we need the molar mass of ammonia (NH3). The molar mass is the sum of the atomic masses of all atoms in the molecule. Nitrogen (N) has an atomic mass of approximately 14.01 g/mol, and hydrogen (H) has an atomic mass of approximately 1.01 g/mol. Since ammonia has one nitrogen atom and three hydrogen atoms, its molar mass is:

Molar mass of NH3 = 14.01 g/mol (for nitrogen) + (3 × 1.01 g/mol) (for hydrogen) = 14.01 g/mol + 3.03 g/mol = 17.04 g/mol

Step 6: Calculate the mass of ammonia using the number of moles and the molar mass: mass of ammonia = moles × molar mass mass of ammonia = 0.300 moles × 17.04 g/mol = 5.112 g

So, the mass of ammonia dissolved in the 200 mL solution is approximately 5.112 grams.