1-17-2021 Percent composition reading
Which of the following statements are part of the proper calculation of the mass % of O in acetic acid (CH3COOH)? Select all that apply. Multiple select question. a. The molar mass of acetic acid is 31.03 g/mol. b. % O = 53.29% c. The mass of oxygen atoms in a mole of acetic acid is 32.00 g. d. The molar mass of acetic acid is 60.05 g/mol. e. % O = 26.64%
% O = 53.29% The mass of oxygen atoms in a mole of acetic acid is 32.00 g. The molar mass of acetic acid is 60.05 g/mol. Reason: 2×16.00 % O = --------- × 100 = 53.29% 60.05
Which one of the following options gives the correct procedure to calculate the number of moles of a substance given the mass of a sample?
mass/ molar mass
The _____ formula of a compound is an integer multiple of the _____ formula.
molecular; empirical
Which one of the following options gives the correct procedure to calculate the mass of a substance given the number of moles?
moles × 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
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 6.022×1023molecules 2.0 mol × -------------------- = 1.2 × 10^24 molecules of 1mol CH4
What is the mass percent of oxygen in aluminum oxide (Al2O3)?
47.08% 3(16.00) -------- × 100 = 47.08% 101.96
Calculate the correct number of moles AND formula units in 7.3 x 10-3 g of CaSO4. Avogadro's number is 6.022 × 1023.
5.4 × 10-5 moles of CaSO4 3.2 × 1019 formula units of CaSO4
How many grams of KMnO4 correspond to 3.13 × 10^22 formula units of KMnO4? Avogadro's number is 6.022 × 10^23.
8.21 g of KMnO4 1mol KMnO4 158.04g KMnO4 3.13 x 10^22 units KMnO4 × ---------- x ------------------ 6.022×1023units KMnO4 1mol KMnO4
The molecular formula of a compound having an empirical formula NH2 (ℳ = 32.05 g/mol) is N
Blank 1: 2 or two Blank 2: 4 or four
The molar mass of a monatomic element is the numerical value listed on the periodic table expressed in units of g/ _____ . For example, the molar mass of calcium (Ca) is ______ with units of g/____. (Remember to round to four significant digits.)
Blank 1: mol or mole Blank 2: 40.08 Blank 3: mol, mole, or mol of Ca
The ____ ____ of a substance is the mass per mole of a substance, in units of g/mol.
Blank 1: molar or molecular Blank 2: mass
A particular hydrocarbon (a compound consisting only of C and H) contains 14.4% H by mass. If the molar mass of the compound is 85. ± 2 g/mol, what is the molecular formula?
C6H12
Match each compound with the correct mass % of hydrogen (H).
C6H6: 7.74% CH3OH: 12.6% CH2O: 6.71%
Correctly associate each molar mass with its compound.
CCl4: 153.8 g/mol CH2O: 30.03 g/mol SF6: 146.1 g/mol KrF2: 121.8 g/mol
A compound has the empirical formula CH2O. What are the possible options for the molecular formula of this compound? Select all that apply.
CH2O C6H12O6 C2H4O2
Which of the following compounds has the largest molar mass?
H2SO4
Place the steps in order for calculating the molar mass of nitrogen gas, starting with the first step at the top of the list. Instructions
Identify that nitrogen exists as N2 arid find the atomic mass of nitrogen on the periodic table Multiply the atomic mass of nitrogen by 2 in order to calculate its molecular mass Report the molar mass of nitrogen as 28.02 g/mol.
Which of the following statements correctly describe molar mass? Select all that apply.
The molar mass is the mass in grams per mole of the substance. The periodic table can be used to calculate the molar mass of any substance.
Which of the following is NOT involved in determining the empirical formula of a compound from mass percent data?
The molar mass of the compound
Select all the pieces of information that are necessary to calculate the mass % of an element in a given compound.
The molecular or formula mass of the compound The formula of the compound The number of atoms of the element in a molecule or formula unit of the compound
Acetic acid has the formula C2H4O2, while ribose has the formula C5H10O5. Select the statements that correctly describe both the empirical formulas of these compounds and their percent composition by mass.
The two compounds have the same percent composition by mass of their elements. The two compounds have the same empirical formula.
True or false: Both the empirical formula mass (CH) and the molecular formula mass (C6H6) of the hydrocarbon benzene would yield the same mass percent of hydrogen.
True Reason: Both the molecular formula and the empirical formula indicate the composition of the compound and the relative amount of each element present. Both formulas will give the same % composition by mass.
