Question 1: Energy in Matter (20 points) A. A student put a bottle of water and

Question

Question 1: Energy in Matter (20 points)

A. A student put a bottle of water and a can of sugared soda in the freezer to chill them quickly. When she took them out, the bottle of water was frozen but the can of soda was not. Explain why this happened. (4 points)

B. Table sugar (C12H22O11) and table salt (NaCl) look very similar but have very different properties. Compare the properties of the two solids in the following areas. (8 points)

i. Electrical conductivity of solid versus melted states (4 points)

ii. Attractive forces holding the solid together (4 points)

C. A passenger on an airplane finished a 0.5 L bottle of water during the flight and replaced the lid. The cabin pressure and temperature were maintained at 0.75 atm and 22°C during the flight. After landing, he noticed his empty water bottle had collapsed. (8 points)

i. How many moles of gas were in the water bottle? (4 points)

ii. If the pressure after landing was 1.0 atm, what was the volume of the passenger's collapsed water bottle? (Assume the bottle collapsed easily and temperature didn't change.) (4 points)

Explanation / Answer

Ans A) Normally water freezes below Zero degree celcius forming Ice Crystals. The Impurities and dust and the imperfections in bottles enhance the growth of ice crystals and it gets frozen. So when the girl took out the bottle of water from the freezer it was frozen.

Now, the Can of Sugared Soda contains the solute carbon dioxide. The pressurised Can of Sugared Soda keeps the carbon dioxide in the solution as the CANS are cooled. This therefore lowers the freezing point of the solution below that of water at zero degree celcius. Most home used freezers are kept at zero degree celcius and hence this sugared soda solution do not freeze.

Answer B ) Solid ions or compounds of NaCl do not conduct electricity. It needs to be either melted or molten. This is because the electrons in a solid state are not free to move to either the cathode (-ve) or to the anode(+ve). In a liquid state the electrons are free enough to move. When NaCl melts, or dissolves in water, the crystal lattice breaks down and the charged particles are able to move, allowing electricity to be conducted.

C12H22O11, table sugar solution does not conduct an electric current because sugar dissolves in water to produce sugar molecules. These sugar molecules are usually neutral and so are unable to move to opposite ends of cathode and Anode like ions. Nacl is an ionic compound whereas table sugar is a molecular compound. Table sugar is a non electrolyte.

In intermolecular force attractions water uses ion - dipole forces to dissolve table salt whereas water uses dipole - dipole intermolecular force to dissolve table sugar.

In case of table salt, slightly positive hydrogen are attracted to chlorine anions and slightly negative oxygen are attracted to sodium cations.

Answer C) PV = nRT

Hence, 0.75 * 0.5 = n * 8.314 * 295

Hence, n = 1.53 * 10 ^ -4.

Therefore, moles of gas in the water bottle were = 1.53 * 10 -4  moles.

Now given,

pressure during landing = 1 atm.

Hence, volume = 1.53 * 10 -4 * 8.314 * 295 = 0.38 litres.

Thus, volume of passenger's collapsed bottle = 0.38 litres.

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