Chemistry- Chapter 3

Which of the following statements correctly describe the percent yield in a chemical reaction? Select all that apply.

-% yield = actual yield-theoretical yield /actual yieldtheoretical yield × 100 -The actual yield is almost always less than the theoretical yield.

The balanced equation 2S(s) + 3O2(g) → 2SO3 (g) is given. The number of moles of SO3 that will form from the complete reaction of 1.5 mol of O2 is given by _____.

-1.5 mol O2 x 2mol SO3/3mol O2

Which of the following statements describe the information that can be gained from a balanced chemical equation? Select all that apply.

-The identities of substances involved. -The physical states of reactants and products, often. -The relative quantities (moles) of substances involved.

Which items of information are necessary to calculate the mass percent of an element in a given compound? Select all that apply.

-The molar mass of the compound -The number of moles of the element in one mole of the compound -The formula of the compound

Which of the following provides the correct mathematical operation to calculate the number of molecules in 2.0 mol of CH4?

2.0 mol × 6.022 × 1023 molecules/mol

Which convention is used in this textbook for rounding off atomic masses based on the periodic table?

Atomic masses are rounded to 4 significant figures.

Combustion analysis is commonly used to determine the empirical formula of unknown compounds containing principally C and H. For a compound containing C, H, and O only, which of the following statements is INCORRECT?

The amount of oxygen is determined from the mass of H2O produced.

Which one of the following options gives the correct procedure to calculate the mass of a substance given the number of moles?

moles x molar mass

Which of the following provides the correct mathematical operation to convert the number of atoms of a sample to the number of moles?

number of atoms/Avogadro's number