food2400 UNIT 2

Consider the melting points of the substances below (see figures for two compounds). Explain the trend in melting point using your knowledge of intermolecular forces. (In the structures below, carbon is black, hydrogen is white, and oxygen is red.) Substance Melting Point (°C) Molar Mass (g/mol) Cl2 −102 71 Ethyl formate (CH3CH2OCHO) −80 74 Propionic acid (CH3CH2COOH) −20 74 Br2 −7.2 160

5. Methane clathrate also called methane hydrate is a form of ice in which methane gas has been trapped inside the crystal structure. Methane hydrate has the formula CH4-5% H20 or 4CH4-23H20. Large quantities of methane hydrate have been discovered in ocean sediments around the world. Mining these deposits to obtain methane (i.e. natural gas) has been discussed for years. Determine the percent water in methane hydrate. How many moles of methane could be recovered from 1.00 ton (2000 Ibs) of methane hydrate? [1 kg = 2.2 Ibs] Methane Water. METHANE CLATHRATE

As water cools to a temperature of zero degrees Celsius and forms ice, water molecules tend to move farther apart. vībrate rapidly. flow more randomly. gradually expand.

MN4.

Which has the highest melting point? CH3OH, CCl4. CH3Cl, KCl, or BCl3

The approximate molar mass of a volatile liquid can be determined by:1. Heating a sample of the liquid in a flask with a tiny hole at the top, which converts the liquid into gas that may escape through the hole2. Removing the flask from heat at the instant when the last bit of liquid becomes gas, at which time the flask will be filled with only gaseous sample at ambient pressure3. Sealing the flask and permitting the gaseous sample to condense to liquid, and then weighing the flask to determine the sample’s mass as shown.

There are three sets of sketches below, showing the same pure molecular compound (ammonia, molecular formula NH₂) at three different temperatures. The sketches are drawn as if a sample of ammonia were under a microscope so powerful that individual atoms could be seen. Only one sketch in each set is correct. Use the slider to choose the correct sketch in each set. You may need the following information: melting point of NH3: -77.7 °C boiling point of NH₁: -33.3 °C B (Choose one) (Choose one) (Choose one) -59, °C -89, °C 54, °C

● Explain why higher average kinetic energy results in higher vapor pressure in terms of IMFs.

Determine what is being asked in each item.   What specific type of intermolecular force causes the increase of boiling point in alcohol molecules? What reduces the intermolecular attraction in hydrocarbons resulting to a decrease of boiling? What is the measurement for the average kinetic energy of particles? What substance is found to be liquid under pressured conditions but is gaseous in normal atmospheric pressure? What is formed when gas is enclosed in a chamber then liquified under very high pressure? * What is the vertical distance from mean sea level to the site being measured that affects boiling point? What is the process of vaporization called? What latent heat value signifies the lost of heat during a phase change? What is the property of molecules and materials of having identical physical properties in all directions? What is the ability of a solid substance to crystallize into more than one different crystal structure? What is the unique temperature and pressure at which…

2. What important information does the melting point of a substance provide?

2. Lead has a face centered cubic lattice with all atoms at the lattice points and a unit cell edge length of 495 pm. Its atomic weight is 207.2 g/mol. What is the density of lead in pounds per cubic feet?

What is the best description of conductivity? Choose one:  The ability of a substance to break apart into ions The presence of charged ions in a substance The amount of electricity present in a substance The degree to which electricity passes through a substance

Which statement best describes the differences in the melting temperatures (Tm) of CaO and MgO? Tm (MgO) Tm (CaO) : Stronger ionic forces due to smaller distance between the ions (size) Tm (MgO) Tm (CaO) : Stronger ionic forces due to greater ionic charges (charge product)

The melting point of calcium is 851 oC, its solid-state specific heat (Csolid) is 0.632 J/goC, and its heat of fusion (ΔHfus) is 233 J/g. How much energy, in joules, is required to melt 120.0 g of calcium at each of the following initial temperatures? (molar mass Ca is 40.08 g/mole)   a.) its melting point b.) 35.0 oC c.) 685 oC below its melting point

There are three sets of sketches below, showing the same pure molecular compound (ammonia, molecular formula NH3) at three different temperatures. The sketches are drawn as if a sample of ammonia were under a microscope so powerful that individual atoms could be seen. Only one sketch in each set is correct. Use the slider to choose the correct sketch in each set. You may need the following information: melting point of NH3: -77.7 °C boiling point of NH3: -33.3 °C A B 63. °C (Choose one) (Choose one) (Choose one) -55. °C C X 3 -98. °C OU Ar

There are three sets of sketches below, showing the same pure molecular compound (ammonia, molecular formula NH3) at three different temperatures. The sketches are drawn as if a sample of ammonia were under a microscope so powerful that individual atoms could be seen. Only one sketch in each set is correct. Use the slider to choose the correct sketch in each set. You may need the following information: melting point of NH3: -77.7 °C boiling point of NH3: -33.3 °C (Choose one) (Choose 1 2 3 4 5 I B - 59. °℃ one) (Choose one) (Choose one) 1 2 3 41. °C I 5 1 3 4 5 I -89. °℃

Consider the data in the table. Compound Melting point (°C) AH (kJ/mol) Boiling point (°C) AHap (kJ/mol) HF -83.11 4.577 19.54 25.18 HCI -114.3 1.991 -84.9 17.53 HBr -86.96 2.406 -67.0 19.27 HI -50.91 2.871 -35.38 21.16 Using the data in the table, calculate ASt and AS for HCI. AStn 12.53 J/(K mol) AS. = 93.12 J/(K mol) Determine the entropy change when 3.50 mol HCI(1) freezes at atmospheric pressure. AS = J/K TOOLS