Chem 211 Smartbook Assignment 3
Which of the following statements correctly describe the empirical formula for a compound? Select all that apply.
Different compounds can have the same empirical formula. The empirical formula of a compound gives the smallest whole number ratio of atoms in a compound.
Which of the following compounds has the largest molar mass?
H2SO4
Which of the following statements correctly describe isomers? Select all that apply.
Isomers are compounds with the same empirical formula. Isomers are compounds with the same molar mass. Isomers are compounds with the same molecular formula.
Which of the following steps are necessary to calculate the mass percent of oxygen in acetic acid (CH3COOH)? Select all that apply.
Multiply the moles of oxygen in the molecular formula by the molar mass of oxygen and then divide by the mass of one mole of acetic acid. Multiply the answer by 100 to find the mass percent of oxygen in acetic acid. Calculate the molar mass of acetic acid from its formula.
Which of the following statements correctly interpret the balanced chemical equation 4HCl (aq) + MnO2 (s) → MnCl2 (aq) + 2H2O (g) + Cl2 (g)? Select all that apply.
The MnCl2 produced is dissolved in water. HCl is a reactant in this equation.
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.
What is the only additional information needed to calculate the empirical formula of a compound if the masses of each element of the compound are provided?
The molar mass of each element
Which of the following correctly reflect Avogadro's number? Choose all that apply.
The mole contains 6.022 x 1023 entities. The number of entities in a mole is called Avogadro's number.
Which of the following options identify the correct coefficients required to balance the reaction illustrated? In the illustration, carbon is black and oxygen is red. Select all that apply.
The reactant CO must have the coefficient 2. CO2 is a product and has the coefficient 2.
Given the balanced equation Ag2S(s) + 2HCl(aq) → 2AgCl(s) + H2S(g), determine the moles of HCl required and the mass of AgCl formed from the complete reaction of 18.3 g of Ag2S.
0.148 mol HCl are required. 21.2 g of AgCl are formed.
Iodine trichloride is produced in a two-step process, represented by the following balanced equations: I2 (s) + Cl2 (g) → 2ICl (s)I2 (s) + Cl2 (g) → 2ICl (s); and ICl (s) + Cl2 (g) → ICl3 (s)ICl (s) + Cl2 (g) → ICl3 (s). Select all the statements that correctly describe how to write a complete balanced equation for the overall process.
The second equation must be multiplied by 2. The overall equation is given by I2 (s) + 3Cl2 (g) → 2ICl3 (s)I2 (s) + 3Cl2 (g) → 2ICl3 (s).
Empirical formula Molecular formula structural formula
The simplest whole-number ratio of moles of each element in a compound Actual number of atoms of each element in a molecule Shows the relative placement and connections of atoms in a molecule
Given the balanced equation 3H2(g) + N2(g) → 2NH3(g), calculate the mass of NH3 produced by the complete reaction of 2.55 g of H2.
14.4 g
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
1.52 × 1024 atoms of Au correspond to __________________mol of Au atoms. Report your answer to 3 significant figures, using decimal notation (NOT scientific notation). (Avogadro's number is 6.022 × 1023.)
2.52
Which of the following options give the correct number of moles AND the correct number of atoms in a 3.54-g sample of copper (Cu)? Avogadro's number is 6.022 × 1023. Select both correct answers.
3.35 × 10^22 atoms of Cu 5.57 × 10^-2 mol of Cu
What is the mass percent of oxygen in aluminum oxide (Al2O3)?
47.08%
A reaction is expected to produce 83.5 g of CaCO3. The percent yield is recorded as 62.5%. What is the actual mass of CaCO3 obtained?
52.2
Which of the following correctly reflects Avogadro's number?
6.022×10^3/1mol
C6H6 CH3OH CH2O
7.74% 12.6% 6.71%
A particular reaction is expected to yield 125 g of calcium. The actual amount of calcium obtained is equal to 105 g. Calculate the percentage yield for the reaction.
84.0%
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.
Compound B2 (represented by the red spheres) reacts with AB, as shown in the illustration. From the illustration, the reagent in excess is _____, and the limiting reagent is _____.
B2; AB
Correctly associate each molar mass with its compound.
CCL4 153.8 CH2O 30.03 SF6 146.1 KrF2 121.8
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 x molar mass
A chemical equation must be balanced. This means that the same _____ and _____ of atoms must appear on both sides of the equation.
number; type
The compounds depicted are _________isomers because they have the same___________ formula but have different_____________ formulas.
structural, molecular, structural
The number of entities in a mole (to 4 significant figures) is equal to_________________ multiplied by 10 to the power of_________________ and is called Avogadro's number..
6.022, 23
Which one of the following options gives the correct procedure to calculate the number of moles of a substance given the mass?
Given Mass/ Molar mass
A nitrogen oxide contains 30.45% N mass. If the molar mass of the compound is 90. ± 5 g/mol, what is its molecular formula?
N2O4
Correctly order the steps necessary to balance a chemical equation. Start with the first step at the top of the list.
Write a skeleton equation Balance the atoms Adjust the coefficients such that they are the smallest whole-number coefficients Do a final check to make sure the equation is balanced
B2 reacts with AB to form AB2 according to the balanced equation B2 + 2AB → 2AB2. If 1.5 moles of B2 are reacted with 1.5 moles of AB, the maximum amount of AB2 that can form is equal to _____ moles.
1.5
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
One molecule of Br2 has a mass of _____________amu; thus, one mole of Br2 molecules has a mass of _________________grams. (Remember to round off atomic masses to 4 significant digits.) Use the periodic table furnished in your book to answer this question correctly.
159.8 and 159.8
Which of the following statements correctly describe the information conveyed by the balanced equation 16Cu (s) + S8 (g) → 8Cu2S (s)? Select all that apply.
16 atoms of Cu react with 1 molecule of S8 to form 8 formula units of Cu2S. 16 moles of Cu react with 1 mole of S8 to form 8 moles of Cu2S. Cu and S8 are reactants and Cu2S is the product.
Identify the whole number coefficients required to balance the chemical equation SO2(g) + O2(g) → SO3(g) correctly. (Enter ALL numbers, including the digit 1 if required, and make sure you have the simplest ratio of coefficients.)
2 SO2 1 O2 2 SO3
Given the balanced equation 2Al(s) + 3Cl2(g) → 2AlCl3(s), select all the conversion factors that correctly represent the molar relationships in this equation.
2 mol Al/3 mol Cl2 2 mol AlCl3/3 mol Cl2
The molecular formula of a compound having an empirical formula NH2 (ℳ = 32.05 g/mol) is N______________ H ._____________
2, 4
1.52 × 1024 atoms of Au correspond to ________________________mol of Au atoms. Report your answer to 3 significant figures, using decimal notation (NOT scientific notation). (Avogadro's number is 6.022 × 1023.)
2.52
The mass % of Ca in CaSO4 is 29.45%. To calculate the mass of Ca present in a 25.6-g sample of this compound, the correct procedure is given by _____.
29.45/100 * 25.6
When hydrogen gas is passed over powdered iron(III) oxide, iron metal and water vapor are formed. Which of the following is the correct balanced equation for this process?
3H2(g) + Fe2O3(s) → 2Fe(s) + 3H2O(g)
Atomic masses are commonly read from the periodic table to __________________significant figures. The atomic mass of H is therefore equal to ______________________amu, whereas the atomic mass of C is equal to_____________________ amu. Use the periodic table given in your textbook to answer the question.
4, 1.008, 12.01
Balance the unbalanced equation given and match each substance to the correct coefficient as indicated.
Al2S3 1 H2o 6 Al(OH)3 2 H2S 3
Correctly order the steps necessary to calculate the empirical formula of a compound, assuming that the masses of each element of the compound are provided. Start with the first step at the top of the list.
Calculate the number of moles of each element of the sample using mass/molar mass Write a chemical formula containing fractional subscripts Divide each subscript by the smallest subscript if integers are not obtained, multiply each subscript by the smallest integer that gives all integer subscripts Verify that the integer subscripts cannot be divided by a common factor
True or false: In order to balance the reaction of hydrogen gas (H2) with oxygen gas (O2) to form liquid water (H2O), a student adds a subscript of 2 after the oxygen in H2O. This is an acceptable method of balancing the above reaction.
False
True or false: To calculate the overall percent yield for a multistep process, add the individual percent yields together.
False
A useful method for keeping track of quantities in a chemical reaction is a reaction table. Which of the following are components of a reaction table? Select all that apply.
Final amounts of reactants and products remaining after the reaction Initial amounts of reactants and products before reaction Change in the amounts of reactants and products during the reaction A balanced chemical equation
Which of the following actions are permitted in balancing a chemical equation? Select all that apply.
Inserting coefficients in front of formulas of reactants and products Multiplying all coefficients by a common factor
Which of the following statements correctly describe the percent yield in a chemical reaction? Select all that apply.
The actual yield is almost always less than the theoretical yield. % yield = actual yieldtheoretical yieldactual yieldtheoretical yield × 100
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 of the following pieces of information is/are necessary to calculate the molar mass of a compound? Select all that apply.
The atomic masses of each of the elements that make up the compound The formula of the compound
Hydrogen and oxygen react to form water according to the balanced equation 2H2 (g) + O2 (g) → 2H2O (l). In a particular reaction vessel, 2.2 mol of H2 are reacted with 2.2 mol of O2. Which of the following options correctly describe how to complete the reaction table given? Select all that apply.
The change in moles of H2 (a) is equal to -2.2. The change in moles of O2 (b) is equal to -1.1. Identify H2 as the limiting reactant.
Hydrogen and nitrogen react to form ammonia according to the balanced equation 3H2 (g) + N2 (g) → 2NH3 (g). In a particular reaction vessel, 4.5 mol of H2 are reacted with 4.5 mol of N2. Which of the following options correctly describe how to complete the reaction table given? Select all that apply.
The final quantity of NH3 present is 3.0 mol. The change in moles of N2 (a) is equal to -1.5.
Which of the following statements correctly describe molar mass? Select all that apply.
The molar mass of a substance is the mass per mole of its entities. When referring to the mass per mole of an entity, the term "entities" could refer to atoms, ions, molecules, or formula units. The periodic table can be used to calculate the molar mass of any substance.
Which items of information are necessary to calculate the mass percent of an element in a given compound? Select all that apply.
The number of moles of the element in one mole of the compound The molar mass of the compound The formula of the compound
Under certain conditions, the reaction of propane and water will produce carbon dioxide and hydrogen gas. The reaction may be represented as a two-step process: C3H8 (g) + 3H2O (g) → 3CO (g) + 7H2 (g) CO (g) + H2O (g) → CO2 (g) + H2 (g) Select the statements that correctly describe how to write a complete balanced equation for the overall process. Select all that apply.
The overall equation is given by C3H8 (g) + 6H2O (g) → 3CO2 (g) + 10H2 (g) The second equation must be multiplied by 3.
Which of the following choices describe the steps required to determine the empirical formula of a compound from the mass percent? Select all that apply.
The ratio of atoms of each element must be a ratio of integer numbers. If a compound contains 52% of mass of C, it can be assumed that there are 52 g of C in 100 g of the compound. The mass percentage of each element is converted to moles using the mass formula mass/molar mass
Match each type of reaction yield to the correct description.
Theoretical yield - The amount of product calculated from the molar ratio in the balanced chemical equation Actual yield - Amount of product obtained experimentally from a chemical reaction Percent yield - Actual yield/ theoretical yield * 100
Which of the following steps would be required to convert between the masses of any two substances involved in the same chemical reaction? Select all that apply.
Write a balanced chemical equation for the reaction. Convert from the given mass to moles of the same substance. Write a conversion factor using the coefficients from the balanced equation, and convert to moles of the second substance.
Correctly order the steps necessary to solve for the mass of a product, or second reactant required, given the mass of one of the reactants in a chemical process. Start with the first step at the top of the list.
Write a balanced equation for the reaction Convert the given mass into moles using molar mass. Convert moles of A to moles of B using a conversion factor derived from the balanced equation Convert the moles of the second substance to mass using its molar mass
The _______ gives the smallest whole number ratio of moles of each element in a compound. Therefore, multiple compounds may have it in common.
empirical formula
A chemical equation is a statement using chemical ________that expresses both the identities and the relative__________ of the reactants and products involved in a chemical or physical change.
formulas, amount
A chemical equation is a statement using chemical_____________ that expresses both the identities and the relative______________ of the reactants and products involved in a chemical or physical change.
formulas, quantity
In order to calculate the mass of an element in a given sample of a compound, the mass of the compound is multiplied by the mass __________________of the element in the compound.
fraction
The mole relates the atomic mass of an element expressed in amu with the mass of 1 mole of that element expressed in___________________ . The mass of 1 mole of oxygen atoms is therefore equal to___________________ g (to 4 significant figures). Use the periodic table given in this book to answer this question correctly.
grams, 16.00
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 4 significant digits.)
mol, 40.08, mol
The ______________mass of a substance is the mass per mole of its entities, where the term "entities" can describe_________________ , ions, molecules, or formula units.
molar, atoms
The ________________is the SI unit that expresses the amount of substance. Specifically, it is defined as the amount of substance containing the same number of ____________________entities as the number of in exactly 12 g of carbon-12.
mole, atoms
In order to calculate the overall % yield for a multistep process ___________.
multiply the individual % yields by each other
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/ Avogradro's number
In a limiting-reactant problem, the final quantities in a reaction table will show ______.
the amount of the reactant in excess one of the reactants totally consumed (final amount is zero)
Place the steps in order for calculating the molar mass of nitrogen gas, starting with the first step at the top of the list.
1. Identify that nitrogen exists as N2, and find the atomic mass of nitrogen on the peridic table 2. Multiply the atomic mass of nitrogen by 3 in order to calculate its molecular mass 3. Report the molar mass of nitrogen as 28.02 g/mol
Arrange the necessary steps in order for finding the molecular formula of an unknown compound from mass percent data. Place the first step at the top of the list.
Assume that the sample contains 100.0 g of compound and express each mass percent as a mass in grams Convert the mass of each element to moles of each element Derive the empirical formula looking for the simplest whole-number ratio of moles Divide the molar mass of the compound by the mass of empirical formula in order to find a multiple that is an integer Multiple each subscript of the empirical formula by the integer multiple
A compound has the empirical formula CH2O. What are the possible options for the molecular formula of this compound? Select all that apply.
C6H12O6 CH2O C2H4O2
Which of the following statements correctly describe the steps used to determine which reactant in a given reaction is limiting? Select all that apply.
Calculate the molar masses of any reactants for which a mass has been given. Calculate the amount of product that could be formed from each reactant. The reactant that produces the least amount of possible product is the limiting reactant.
Which step is INCORRECT to determine the molecular formula for a compound using combustion analysis data?
Determine the mass of a third element, if present, from the mass of its oxide produced in the combustion.
Correctly order the steps necessary to determine the molecular formula for a compound using combustion analysis data. Start with the first step at the top of the list.
Determine the masses of carbon and hydrogen from the masses of CO2 and H2O respectively Determine the mass of oxygen, if present, by subtracting the masses of carbon and hydrogen from the total mass Determine the number of moles of each element in the compound and hence the empirical formula Determine the molecular formula using the empirical formula and the milar mass
Correctly order the steps necessary to calculate the mass of product formed in a chemical reaction, given the masses of all reactants. Start with the first step at the top of the list.
Determine the moles of each reactant present by diving its mass by its molar mass Determine the amount of product that could be formed from each reactant using the appropriate mole ratios Identify the limiting reactant as the reactant that produces the least amount of product To find the mass, multiply the nukber of moles of product formed (from the limiting reactant) by the molar mass of the product
Which of the following statements describe combustion analysis correctly? Select all that apply.
Every 1 mole of carbon in the compound will produce 1 mole of CO2. Combustion analysis involves burning a compound in O2. The mass of hydrogen in the compound is determined from the amount of H2O produced.
