Question 1: Which statement describes the quantities that can be found using the number of moles?
Answer: It can be used to find the number of molecules, atoms, or ions.
Question 2: A scientist uses 3 g of water (H2O) in an experiment. Which option describes the first step in calculating the number of molecules in 3 g of water?
Answer: Identify the molar masses of H and O.
Question 3: The molar mass of ammonia (NH3) is 17.03 g/mol. Which expression correctly shows how to determine the number of moles of ammonia equivalent to 5 g?
Answer: 5 g×1 mol/17.03 g
Question 4: How many molecules of carbon dioxide (CO2) are there in 0.450 mol of carbon dioxide?
Answer: 2.71×1023
Question 5: When magnesium chloride (MgCl2) is dissolved in water, which statement must be true?
Answer: The sum of the mass of the Mg2+ ions and the mass of the Cl– ions must be equal to the mass of MgCl2.
