1. Finding the volume of a flask. A student obtained a clean, dry glass-stoppered flask. She weighed the flask and stopper on an analytical balance and found the total mass to be 33.695 g. She then filled the flask with water and obtained a mass for the full stoppered flask of 64.356 g. From these data, and the fact that at the temperature of the laboratory the density of water was 0.9978 g/cm3, find the volume of the stoppered flask. a. First we need to obtain the mass of the water in the flask. This is found by recognizing that the mass of a sample is equal to the sum of the masses of its parts. For the filled stoppered flask: Mass of filled stoppered flask = mass of empty stoppered flask + mass of water, So mass of water = mass of filled flask – mass of empty flask Mass of filled flask = 64.356g Mass of empty flask = 33.695g So mass of water = 64.356g – 33.695g = 30.661g Many mass and volume measurements in chemistry are made by the method used in 1a. This method is called measuring by difference, and is a very useful one. b. The density of a pure substance is equal to its mass divided by its volume: Density = Mass/Volume or Volume = Mass/Density The volume of the flask is equal to the volume of the water it contains. Since we know the mass and density of the water, we can find its volume and that of the flask. Make the necessary calculation. Thus, Volume of water = 30.661g / 0.9978g/cm 3 = 30.73cm 3 Volume of water = 30.73 cm 3 2. Finding the density of an unknown liquid..
Answers & Comments
Answer:
1. Finding the volume of a flask. A student obtained a clean, dry glass-stoppered flask. She weighed the flask and stopper on an analytical balance and found the total mass to be 33.695 g. She then filled the flask with water and obtained a mass for the full stoppered flask of 64.356 g. From these data, and the fact that at the temperature of the laboratory the density of water was 0.9978 g/cm3, find the volume of the stoppered flask. a. First we need to obtain the mass of the water in the flask. This is found by recognizing that the mass of a sample is equal to the sum of the masses of its parts. For the filled stoppered flask: Mass of filled stoppered flask = mass of empty stoppered flask + mass of water, So mass of water = mass of filled flask – mass of empty flask Mass of filled flask = 64.356g Mass of empty flask = 33.695g So mass of water = 64.356g – 33.695g = 30.661g Many mass and volume measurements in chemistry are made by the method used in 1a. This method is called measuring by difference, and is a very useful one. b. The density of a pure substance is equal to its mass divided by its volume: Density = Mass/Volume or Volume = Mass/Density The volume of the flask is equal to the volume of the water it contains. Since we know the mass and density of the water, we can find its volume and that of the flask. Make the necessary calculation. Thus, Volume of water = 30.661g / 0.9978g/cm 3 = 30.73cm 3 Volume of water = 30.73 cm 3 2. Finding the density of an unknown liquid..