Problem on heat capacity and enthalpy

Question

Assignment:

Question 1. Calculate the amount of heat that must be absorbed by 10.0 g of ice at -20^oC  to convert it to liquid water at 60.0^oC. Given: Specific heat (ice)=2.1 J/g^oC Specific heat(water)=4.18 J/g^oC H (fus)=6.0 kJ/mol

• 420 J
• 2,900 J
• 6,300 J
• 63 kJ
• 7.5 J

Question 2. The major enthalpy of Boron tribromide (BBr₃) is 30.5 kJ/mol, and its normal boiling point is 91^oC. What is the vapor pressure of BBr₃ at 20^oC?

• 11.5 torr
• 311 torr
• 5.31 torr
• 143 torr
• 66.1 torr

Question 3. Each of the following substances is a liquid at -50^oC. Place these liquids in order of increasing vapor pressure: Dimethyl ether (CH₃OCH₃), propane (C₃H₈), ethanol (CH₃CH₂OH).

• Ethanol
• Ethanol
• Propane
• Dimethyl ether
• Propane

Question 4. Platinum (Pt) has a face centered cubic crystal  structure and a density of 21.5 g/cm3. What is the radius of the platinum atom(pm:picometer).

• 69 pm
• 98 pm
• 139 pm
• 196 pm
• 277 pm