Having trouble solving these 3 problems. please help or advise.
1. When camping in remote locations, water can be in short supply. It is not
practical to carry all of the water needed during a trip from the starting
point to the campsite. Hikers often look for other sources of potable
(drinkable) water near their campsite. During the winter months, it is
possible to melt clean snow and turn it into drinkable water. To warm
themselves, campers make pots of “trail coffee” – coffee grounds boiled in
a pot with water.
a. Two hikers in Acadia National Park melt snow to make 1000. mL of
trail coffee. If the snow used is originally at –10 °C, how much
energy is required to heat the water to its boiling point? [Cp(ice) =
37.1 J/mol °C; ?Hfus = 6.01 kJ/mol; Cp(H2O) = 75.3 J/mol °C]
Assume that the density of snow and liquid water are both 1.00
b. To boil the water, a small propane-fueled stove is commonly used.
Given that the heat of combustion (?H°c) of propane (C3H8) is –
2220. kJ mol-1, please calculate the number of moles of propane
needed to melt the water.
c. Propane is usually sold in 400 g fuel canisters. How many canisters
would you need to make the coffee?
2. A 1.00% by mass NaCl(aq) solution has a freezing point of -0.192 C.
a. Estimate the van’t Hoff factor (i) from the data.
b. Determine the molal concentrations of Na+. Cl-, and NaCl.
c. Calculate the percent dissociation of NaCl in this solution.
(Hint: When calculating freezing point depression, the
concentration (m*i) is the sum of the molalities of Na+. Cl-, and
3. In the human liver, the oxidation of ethanol (from alcoholic beverages) to
acetaldehyde, catalyzed by the enzyme by alcohol dehydrogenase, is a
CH3CH2OH + NAD+ ? CH3CHO + NADH + H+
An average 70-kg person typically takes about 2.5 hrs to oxidize the 15 mL
of ethanol (C2H5OH; density = 0.7893 g mL-1) contained in a single 12-oz
can of beer, 5-oz glass of wine, or one shot of distilled spirits.
a. Which plot will be linear - [ethanol] vs. time, ln [ethanol] vs. time,
or 1/[ethanol] vs. time?
b. What is the rate law for this reaction?
c. What is the value of the rate constant for this reaction? Be sure to
include the proper units.
d. The actual rate of oxidation varies greatly from person to person.
What causes this discrepancy? (Assume that all people have the
same body temperature of 98.6 ºF.)