Question 1: Define concentration in the context of chemistry.

Answer: Concentration refers to the amount of a substance (solute) present in a given volume or mass of solution or mixture.

Question 2: Explain why concentration is important in chemical reactions.

Answer: Concentration affects the rate and extent of chemical reactions by determining how many particles are available to interact.

Question 1: Calculate the molarity of a solution prepared by dissolving 5 grams of sodium chloride (NaCl) in 250 mL of water. (Molecular weight of NaCl = 58.44 g/mol)

Answer: M = (mass in grams / molecular weight) / volume in liters = (5 / 58.44) / 0.250 = approximately 0.341 mol/L

Question 2: A solution contains 0.2 mol of sulfuric acid (H₂SO₄) in 2 liters of solution. What is its concentration in molarity?

Answer: Concentration = moles / volume in liters = 0.2 / 2 = 0.1 mol/L

Question 1: Describe a safe procedure for preparing a 1 M solution of sodium hydroxide (NaOH). Include safety precautions.

Answer: First, wear safety goggles and gloves. Carefully add solid NaOH to a beaker containing a small amount of water while stirring. Continue adding water until the total volume reaches 1 liter. Handle NaOH with care as it is caustic. Always add NaOH to water, not vice versa, to prevent splashing.

Question 2: Identify the independent, dependent, and control variables in an experiment where you dilute a concentrated solution to achieve a desired concentration.

Answer: Independent variable: amount of solvent added; Dependent variable: concentration of the solution; Control variables: initial concentration, temperature, type of solvent.

Question 1: A student measures the concentration of a sugar solution at three different times: 0.5 mol/L, 0.3 mol/L, and 0.1 mol/L. What could cause the decrease in concentration over time? Provide at least two possible explanations.

Answer: Possible causes include the sugar being used up in a chemical reaction or the solution evaporating, leading to a lower concentration.

Question 2: A sample of a solution has a total mass of 50 grams, of which 10 grams is the solute. Calculate the concentration in grams per 100 mL if the solution volume is 200 mL.

Answer: Mass of solute = 10 g; concentration = (mass of solute / volume in mL) * 100 = (10 / 200) * 100 = 5 g/100 mL

Question 1: Explain how understanding concentration is important in the food industry, such as in the production of fruit juices.

Answer: Concentration determines the sweetness, flavor, and preservative qualities of fruit juices. Accurate concentration ensures product consistency and safety for consumers.

Question 2: Describe a scenario where incorrect concentration could lead to a safety issue in a household or industrial setting.

Answer: Using too concentrated a cleaning solution can cause skin burns or respiratory problems, while too dilute solutions may be ineffective, leading to unsanitary conditions or failure to disinfect properly.