Making a solution with quantity (moles!)
In order to create a solution with known quantitative numbers, we must re-visit the mole.
To quantify the amount found in a solution, the concentration is calculated by the amount of moles in a solution. Molarity or concentration is the proper terminology in identifying the amount of moles per volume.
The units for Molarity is moles/L.
Since the Molarity contains the # of moles in a specified volume, M or Molarity can be converted into Particles, Grams, or Litres of gas through the same conversion. As in for all molar conversion, moles must be the center of the conversion and be calculated first.
Example 1. What is the molarity of a 5.00 liter solution that was made with 10.0 moles of KBr ?
V = 5.00L
Moles = 10.0 moles KBr
Molarity = 10.0 moles / 5.0 = 2.0M of KBr
The amount of particles found in the 5.00L or the mass of KBr in the 5.00L can be also converted as long as moles are calculated first and then further converted into the desired unit.
Example 2. A 250 ml solution is made with 0.50 moles of NaCl. What is the Molarity of the solution?
V = 250ml or 0.25L
Moles = 0.50moles of NaCl.
Molarity = 0.50 / 0.25 = 2.00L NaCl
Why this is important?
Calculating molarity is important in solutions or solute dissolved in a solvent. The molarity allows a specified amount of quantity found in a volume that can be further be calculated / converted into grams, particles / molecules / ions. Molarity provides the method in knowing the exact amount of a substance to dissolve into a said volume to provide the exact concentration! Cool!
- Describe and give examples of various types of solutions. Include: all nine possible types
- Describe the structure of water in terms of electronegativity and the polarity of its chemical bonds.
- Explain the solution process of simple ionic and covalent compounds, using visual, particulate representations and chemical equations. Include: crystal structure, dissociation, hydration
- Interpreting a a solubility curve of a pure substance in water and differentiate among saturated, unsaturated, and supersaturated solutions.
- Explain how a change in pressure affects the solubility of gases.
- Explain freezing-point depression and boiling-point elevation at the molecular level. Examples: antifreeze, road salt…
- Include: grams per litre (g/L), % weight-weight (% w/w), % weight-volume (% w/v), % volume/volume (% v/v), parts per million (ppm), parts per billion (ppb), moles per litre (mol/L) (molarity)
- Prepare a solution, given the amount of solute (in grams) and the volume of solution (in millilitres), and determine the concentration in moles/litre. (Molarity)
- Solve problems involving the dilution of solutions.
Include: dilution of stock solutions, mixing common solutions with different volumes and concentrations