Chemistry AP Summer Work Help Please?
1.] The density of air at ordinary atmospheric pressure and 25 degrees is 1.19 g/L. What is the mass, in kilgrams, of air in a roo, that measures 8x12x20 ft?
2.] Most solids have a higher density at their melting point than the liquid phase. Suggest a reason why this should be so.
3.] Suppose you decide to define your own temperatur scale using the freezing point (-11.5 degrees celsius) and boiling point (197.6 degrees celsius) of ethylene glycol. If you set the freezing point at 0 degrees "G" and the boiling point at 100 degrees "G", what is the freezing point of water on this new scale?
4.] A cylindral glass tube 15.0 cm in length is filled with ethanol. The mass of ethanol needed to fill the tube is found to be 9.64 g. Calculate the inner diameter of the tube in cm. The density of ethanol is 0.789
if you could help me with these i would really appreciate it. thanks in advance!
Answer:
1. Okay, you know the density of air, which is mass per unit volume. The questions is asking the mass of air in the room, so you need to figure out the volume of air, and just multiply that by the density. The problem is that they give you the volume in feet, but the density is in liters, so you need to convert cubic feet to liters. The room is 8x12x20 = 1,920 cubic feet. From a conversion chart, or some conversion website on the internet, such as this one (http://www.convert-me.com/en/convert/vol... that's the same as 54,370 liters. Since you know air weighs 1.19 g/liter, then the mass of the air in the room is 64,700.3 grams. But you're not quite done. The question asks for the answer in kilograms, not grams. There are 1000 grams per kilogram, so just divide this answer by 1000 to give you 64.7003 kilograms.
2. Can't quite remember the answer to this one. Sorry.
3. Okay, so the new 0G is the old -11.5C, and the new 100G is the old 197.6C. What used to span 209.1 degrees in C now only spans 100 degrees in G. So every degree in G is therefore now worth 2.091 degrees in C. The freezing point of water is 0 C, but now our zero is 11.5 degrees below zero. Therefore the new freezing point of whater is 11.5 x 2.091 = 24.05 G.
4. You know it takes 9.46 g of ethanol to fill the tube, and you know the density of ethanol is 0.789 grams per cubic centimeter. Therefore you know you have 9.46/0.789 = 11.99 cubic centimeters of ethanol. The formula for the volume of a cylinder is Base x height. In this case, the cylinder is on it's side, right? So the height is really just the length, which we know is 15 cm. so 11.99 = 15(x), where x is the area of the base. The base is therefore 11.99/15 = 0.8 square centimeters. The question asks for the diameter. The diameter of a circle (the base of our tube in this case) is pi(r^2), right? so 3.14(r^2) = 0.8. r^2 = 0.25. That means that r = 0.5, and the diameter must therefore be 1.0 cm.
Good luck!
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2.] Most solids have a higher density at their melting point than the liquid phase. Suggest a reason why this should be so.
3.] Suppose you decide to define your own temperatur scale using the freezing point (-11.5 degrees celsius) and boiling point (197.6 degrees celsius) of ethylene glycol. If you set the freezing point at 0 degrees "G" and the boiling point at 100 degrees "G", what is the freezing point of water on this new scale?
4.] A cylindral glass tube 15.0 cm in length is filled with ethanol. The mass of ethanol needed to fill the tube is found to be 9.64 g. Calculate the inner diameter of the tube in cm. The density of ethanol is 0.789
if you could help me with these i would really appreciate it. thanks in advance!
Answer:
1. Okay, you know the density of air, which is mass per unit volume. The questions is asking the mass of air in the room, so you need to figure out the volume of air, and just multiply that by the density. The problem is that they give you the volume in feet, but the density is in liters, so you need to convert cubic feet to liters. The room is 8x12x20 = 1,920 cubic feet. From a conversion chart, or some conversion website on the internet, such as this one (http://www.convert-me.com/en/convert/vol... that's the same as 54,370 liters. Since you know air weighs 1.19 g/liter, then the mass of the air in the room is 64,700.3 grams. But you're not quite done. The question asks for the answer in kilograms, not grams. There are 1000 grams per kilogram, so just divide this answer by 1000 to give you 64.7003 kilograms.
2. Can't quite remember the answer to this one. Sorry.
3. Okay, so the new 0G is the old -11.5C, and the new 100G is the old 197.6C. What used to span 209.1 degrees in C now only spans 100 degrees in G. So every degree in G is therefore now worth 2.091 degrees in C. The freezing point of water is 0 C, but now our zero is 11.5 degrees below zero. Therefore the new freezing point of whater is 11.5 x 2.091 = 24.05 G.
4. You know it takes 9.46 g of ethanol to fill the tube, and you know the density of ethanol is 0.789 grams per cubic centimeter. Therefore you know you have 9.46/0.789 = 11.99 cubic centimeters of ethanol. The formula for the volume of a cylinder is Base x height. In this case, the cylinder is on it's side, right? So the height is really just the length, which we know is 15 cm. so 11.99 = 15(x), where x is the area of the base. The base is therefore 11.99/15 = 0.8 square centimeters. The question asks for the diameter. The diameter of a circle (the base of our tube in this case) is pi(r^2), right? so 3.14(r^2) = 0.8. r^2 = 0.25. That means that r = 0.5, and the diameter must therefore be 1.0 cm.
Good luck!
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