Advanced Conversions, Moles, Percentages & Heat Transfer
Complete all problems showing your work. Use proper significant figures, include units with every step, and check your answers with the answer key when finished. This mixed review covers advanced conversions, mole calculations, percentages, and thermal equilibrium.
Problem 1
A smartphone screen is 6.2 inches long and 2.9 inches wide. What is the area of the screen in square centimeters? (1 inch = 2.54 cm)
Problem 2
A pharmaceutical company produces pills that contain 325 mg of acetaminophen each. If a bottle contains 250 pills, what is the total mass of acetaminophen in the bottle in ounces? (1 oz = 28.35 g)
Problem 3
How many moles of water (H₂O) are in 54.0 grams of water?
Problem 4
A sample of sodium chloride (NaCl) contains \(3.01 \times 10^{23}\) formula units. How many moles of NaCl is this?
Problem 5
How many atoms of carbon are present in 11.0 grams of propane, C₃H₈? (Hint: First find moles of propane, then find moles of carbon atoms, then convert to atoms.)
Problem 6
A brass key has a mass of 12.5 grams and is 65% copper. How many grams of copper are in the key?
Problem 7
The air in a diving tank contains 21% oxygen by volume. If a diver uses 45 liters of air from the tank during a dive, how many liters of oxygen did the diver breathe?
Problem 8
The human body is approximately 0.25% potassium by mass. If a person weighs 68 kg, how many grams of potassium does their body contain? Then, calculate how many moles of potassium atoms this represents. (Molar mass of K = 39.1 g/mol)
Problem 9
How much heat energy is required to raise the temperature of 250 g of water from 20°C to 85°C? (\(c_{\text{water}} = 4.18\) J/g°C)
Problem 10
A 75.0 g piece of copper at 95°C is placed in 200 g of water at 22°C. What will be the final temperature when thermal equilibrium is reached? (\(c_{\text{copper}} = 0.385\) J/g°C, \(c_{\text{water}} = 4.18\) J/g°C)
Hint: Heat lost by copper = Heat gained by water