Free BACE Preparing solutions Questions and Answers — Questions and Answers
Question 1: What is the primary unit of concentration for solutions in a laboratory?
- Mole per liter (Molarity, M) (Correct answer)
- Grams per liter (g/L)
- Milligrams (mg)
- Parts per million (ppm)
Correct answer: Mole per liter (Molarity, M)
Molarity (M), defined as moles of solute per liter of solution, is the primary unit of concentration used in laboratory settings. It provides a precise measure of the number of solute particles in a given volume, which is crucial for chemical reactions and stoichiometric calculations. This unit allows for accurate and reproducible preparation of solutions for various experiments and analyses.
Question 2: What is the volume of water needed to prepare a 1 M NaCl solution using 58.44 g of NaCl?
- 0.5 L
- 1 L (Correct answer)
- 2 L
- 5 L
Correct answer: 1 L
To prepare a 1 M NaCl solution using 58.44 g of NaCl, you need to understand the definition of molarity. The molar mass of NaCl is approximately 58.44 g/mol, meaning 58.44 g constitutes 1 mole of NaCl. A 1 M solution contains 1 mole of solute per liter of solution, so dissolving 58.44 g of NaCl and bringing the total volume to 1 L with water will yield a 1 M solution.
Question 3: Which piece of equipment is most accurate for measuring liquid volumes?
- Beaker
- Graduated cylinder
- Pipette (Correct answer)
- Erlenmeyer flask
Correct answer: Pipette
Pipettes are specifically designed for highly accurate and precise measurement and transfer of liquid volumes, especially small ones. Unlike beakers or graduated cylinders, which are used for approximate measurements, pipettes (such as volumetric or micropipettes) are calibrated to deliver exact volumes. This precision is critical in many laboratory procedures, including preparing reagents and performing quantitative assays.
Question 4: When dissolving a solute in water, what step should be done first?
- Weigh the solute (Correct answer)
- Add water to the final volume
- Stir the solution
- Heat the solution
Correct answer: Weigh the solute
When preparing a solution, the first essential step is to accurately weigh the solute. The amount of solute directly determines the concentration of the final solution. Precise measurement of the solute ensures that the solution will have the desired molarity or percentage concentration, which is critical for experimental accuracy and reproducibility.
Question 5: What does "q.s." mean when preparing a solution?
- Add more solute
- Add sufficient quantity of solvent (Correct answer)
- Heat to dissolve
- Quantify the solute
Correct answer: Add sufficient quantity of solvent
In solution preparation, 'q.s.' stands for 'quantum sufficit,' which is Latin for 'as much as suffices' or 'sufficient quantity.' This instruction means to add enough solvent to reach the final desired volume of the solution. It ensures that the solute is fully dissolved and the solution's concentration is accurately established by bringing it to a precise final volume.
Free BACE Preparing solutions Questions and Answers
What is the primary unit of concentration for solutions in a laboratory?