In this problem we are given density of an

oil and we want to know the mass of three barrels of oil. We want that mass in kg and

it tells us that one barrel of oil is 42 gallons. Then it gives us the conversion of 1 gallon

is 3.8754 L. I am going to solve this problem. This is not a problem that I looked at previously.

I am going to show you the approach I would use to solving this problem. First I would

tend to write down the information that I have in notation. In this case using a symbol

for density that is common. What I want is the mass in kg so this is my unknown. I have

three barrels and 1 barrel is 42 gallons. Then 1 gallon is 3.8754 L. This is a problem

essentially of unit conversion and the easiest way to do unit conversion is to first calculate

the volume of three barrels. It is critical to carry the units through. Three barrels

and 1 barrel is 42.0 gal. I am writing it this way since I am multiplying. Notice those

units cancel and that is the reason I wrote the 1 barrel in the denominator. Likewise

1 gallon is 3.8754 L so gallons cancel. Now I should be able to do this multiplication

to determine how many liters I have. I get 488.3 L. I want the mass so the mass is going

to be the density times the volume. I get 0.85 g per mL. 488.3 L but I need to make

the units cancel to get a mass in kg because the problem asks for kg. 10^3 mL is a L and

10^3 g is a kg so these 10^3 cancel and mL, L, and g cancel. My final answer then will

be in kg. That will be 415.05 kg. I should reduce to have the correct number of significant

figures. If there are only 2 significant figures here then probably should round this off to

420 kg in those three barrels of oil.

Could someone do the conversion of 4.18 kJ K-1 Kg-1 to x BTU F-1 lb-1 at 20 degrees Celsius please. It is supposed to be 0.99 but I keep getting 7.8 or 460 – Nowhere near!