I'm having a little trouble figuring this problem out...

The density and associated percent crystallinity for twopoly(ethylene terephthalate) materials are shown,

(a) Compute the densities of totally crystalline and totallyamorphous poly(ethylene terephthalate). (b) Determine the percentcrystallinity of a specimen having a density of 1.382 g/cm3.

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Elin HesselLv2

30 May 2019

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I'm having trouble converting the units and knowing exactly what they want for part B of this questions. I'm not sure what they want after using the STP of 22.4 to find out density of CH4 and the other gasses, so I'm a little confused on how to convert it to Energy density form.

6) a) Which of CH4(g), C2H2(g), and CH3OH(l) provides the most energy per gram upon combustion and which provides the least?

CH4(g) + 2 O2(g) â CO2(g) + 2 H2O(l) ÎHÂ° = -890 kJ

2 C2H2(g) + 5 O2(g) â 4 CO2(g) + 2 H2O(l) ÎHÂ° = -2599 kJ

2 CH3OH(l) + 3 O2(g) â 2 CO2(g) + 4 H2O(l) ÎHÂ° = -1453 kJ 4

b) Energy density is the amount energy per unit volume.; this is an important consideration in designing automotive fuel systems (how far can I go on a tank of fuel?). Calculate the energy density for each of the fuels at STP (the density of methanol is 0.791 g/mL).

crimsonswan942

(a) To identify a liquid substance, a student determined its density. Using a graduated cylinder, she measured out a 45-mL sample of the substance. She then measured the mass of the sample, finding that it weighed 38.5 g. She knew that the substance had to be either isopropyl alcohol (density 0.785 g/mL) or toluene (density 0.866 g/mL). What are the calculated density and the probable identity of the substance? (b) An experiment requires 45.0 g of ethylene glycol, a liquid whose density is 1.114 g/mL. Rather than weigh the sample on a balance, a chemist chooses to dispense the liquid using a graduated cylinder. What volume of the liquid should he use? (c) Is a graduated cylinder such as that shown in Figure 1.19 likely to afford the accuracy of measurement needed? (d) A cubic piece of metal measures 5.00 cm on each edge. If the metal is nickel, whose density is 8.90 g/cm³, what is the mass of the cube?

Figure .19.

Based on this result, the compound is the most likely toluene.

c) The accuracy of graduated cylinder is not enough this measurement, as the uncertainty in the volume measured with this flask is ±1 mL, and we need a flask with ±0.1 mL accuracy.