How do you calculate the number of grams of solute in 0.250 L of 0.175 M \rm KBr?
Calculate the number of grams of solute in 0.250 L of 0.175 M solution of potassium bromide.
To calculate the number of grams of solute in a given solution, you need to use the relationship between the concentration (in moles per liter) and the molar mass of the solute.
Here's how you can solve the problem step by step:
1. Start by identifying the known values:
- Volume of the solution (V): 0.250 L
- Concentration of the solution (C): 0.175 M
- Molar mass of the solute (MM): You'll need to look that up for potassium bromide (KBr).
2. Convert the concentration from molarity (moles per liter) to moles:
Number of moles (n) = Concentration (C) × Volume (V)
n = 0.175 M × 0.250 L
3. Calculate the mass of the solute using the molar mass:
Mass (m) = Number of moles (n) × Molar mass (MM)
To calculate the molar mass of KBr:
- K (potassium) has a molar mass of approximately 39.10 g/mol
- Br (bromine) has a molar mass of approximately 79.90 g/mol
Since KBr has one potassium atom and one bromine atom, the molar mass of KBr is:
Molar mass (KBr) = Molar mass (K) + Molar mass (Br)
Molar mass (KBr) = 39.10 g/mol + 79.90 g/mol
Now, plug in the values to calculate the mass of the solute:
Mass (m) = n × MM
Mass (m) = 0.175 M × 0.250 L × (39.10 g/mol + 79.90 g/mol)
Calculate the result to get the number of grams of solute in 0.250 L of 0.175 M KBr.
2.51
Just remember the definition of molarity.
M = moles/L; therefore,
moles = M x L. Easy, huh?