Numbers in Chemistry: Mole and Mole Stoichiometry

Question 1

is the sum of the atomic masses of all the atoms represented in the chemical formula of a substance.

Answer 1

Formula mass

Question 2

One mole contains exactly _________ elementary entities

Answer 2

6.02214076 x 10^(23)

Question 3

is the SI unit amount of a substance

Answer 3

mole

Question 4

is the amount of substance that contains the same number of elementary particles as the number of in exactly 12g of Carbon-12

Answer 4

mole

Question 5

Avogadro’s number

Answer 5

6.02214076 x 10^(23)

Question 6

is the mass, in grams, of a substance that is numerically equal
to the substance’s formula mass.

Answer 6

molar mass

Question 7

is the mass, in grams, of one mole of a substance that is equivalent to the atomic mass of an atom or the sum of atomic mass of the elements in a molecule, compound, or ion

Answer 7

molar mass

Question 8

Carbon monoxide (CO) is an air pollutant that enters the atmosphere primarily in automobile exhaust. Calculate the mass in grams of a 2.61-mole sample of this air pollutant.

Answer 8

73.1g CO

Question 9

The compound lithium carbonate, used to treat manic depression, has the formula Li2CO3. Calculate the number of formula units of lithium carbonate present in a 0.500-g sample of lithium carbonate.

Answer 9

4.07 x 10 ^(21) Li2CO3 formula units

Question 10

How many grams of oxygen are present in a 0.10-g sample of adrenaline, a hormone secreted into the bloodstream in times of stress? The formula of adrenaline is C 9 H 13 NO 3 .

Answer 10

0.026g O

Question 11

Balance the following chemical equation.
C4H10O + O2 —> CO2 + H2O

Answer 11

C4H10O + 6O2 —> 4CO2 + 5H2O

Question 12

Silicon carbide, SiC, which is used as an abrasive on sandpaper, is prepared using the
chemical reaction
SiO2 + 3C —> SiC + 2CO
How many grams of SiC can be produced from 15.0 g of C?

Answer 12

16.7 g SiC

Question 13

The chemical equation for the photosynthesis reaction in plants is
6CO2 + 6H2O —> C6H12O6 + 6O2
How many grams of H2O are consumed at the same time that 20.0 g of CO2 is consumed?

Answer 13

8.19g H2O

Question 14

is the maximum amount of a product that can be obtained from given amounts of reactants in a chemical reaction if no losses or inefficiencies of any kind

Answer 14

theoretical yield

Question 15

is the amount of product actually obtained from a chemical reaction.

Answer 15

actual yield

Question 16

is the ratio of the actual (measured) yield of a product in a chemical reaction to the theoretical (calculated) yield multiplied by 100 (to give percent).

Answer 16

percent yield

Question 17

When 12.3 g of H 2 react with N 2 according to the chemical equation
N2 + 3H2 —> 2NH3
55.8 g of NH 3 are obtained. What is the percent yield of NH 3 for this reaction?

Answer 17

80.6%

Question 18

simplest whole-number ratio

Answer 18

empirical formula

Question 19

actual whole-number ratio

Answer 19

molecular formula

Question 20

An analysis of a compound shows 62.04% C, 10.41%H, and 27.55% O. Determine the molecule formula of the compound.

Answer 20

C3H6O

Question 21

A colorless liquid has a composition of 84.1% C and 15.9% H. Find the empirical and molecular formula of this hydrocarbon. The molecular weight of the hydrocarbon is 114.2g/mol.

Answer 21

EF: C4H9
MF: C8H18

Question 22

Describe the process of combustion analysis

Answer 22

A weighed sample of a compound is burned in a stream of oxygen gas
H2O and CO2 is produces in the combustion are absorbed by appropriate substances
The increase in mass of these absorbers corresponds to the masses of H2O and CO2

Question 23

Combustion of a 0.200g vitamin C sample yield 0.2998g CO2 and 0.0819g H2O. What are the percent composition and empirical formula of vitamin C?

Answer 23

%Composition: 40.91%, 4.58%, and 54.50% O
EF: C3H4O3

Question 24

is the quantitative relationship of the amounts of reactants and products formed in a reaction.

Answer 24

chemical stoichiometry

Question 25

A 1.00g sample of which compound will produce the greatest amount of CO2 after complete combustion with excess oxygen? CH4, C3H6, C6H14, C8H18

Answer 25

0.0714 mol CO2 C3H6

Question 26

Urea [(NH2)2CO] is prepared by reacting ammonia with carbon dioxide: 2NH3(g) + CO2(g) ---> (NH2)2CO(aq) + H2O(l) In one process, 637.2 g of NH 3 are treated with 1142 g of CO2. (a) Which of the two reactants is the limiting reagent? (b) Calculate the mass of (NH2)2CO formed. (c) How much excess reagent (in grams) is left at the end of the reaction?

Answer 26

LR: NH3 Mass of (NH2)2CO formed: 1124g (NH2)2CO xss reagent left: 319 g CO2

Question 27

Titanium is a strong, lightweight, corrosion-resistant metal that is used in rockets, aircraft, jet engines, and bicycle frames. It is prepared by the reaction of titanium(IV) chloride with molten magnesium between 9508C and 11508C: TiCl4(g) + 2Mg(l) ---> Ti(s) + 2MgCl2(l) In a certain industrial operation 3.54 x 10^7 g of TiCl4 are reacted with 1.13 x 10^7g of Mg. (a) Calculate the theoretical yield of Ti in grams. (b) Calculate the percent yield if 7.91 x 10^6 g of Ti are actually obtained.

Answer 27

LR: TiCl4 theoretical yield of Ti: 8.95X 10^6 g Ti percent yield: 88.4%

Question 28

Ascorbic acid (vitamin C) cures scurvy. It is composed of 40.92 percent carbon (C), 4.58 percent hydrogen (H), and 54.50 percent oxygen (O) by mass. Determine its Empirical formula.

Answer 28

C3H4O3

Question 29

Chalcopyrite (CuFeS2) is a principal mineral of copper. Calculate the number of kilograms of Cu in 3.71 x 10^3 kg of chalcopyrite.

Answer 29

1.28 x 10^3 kg

Question 30

4.159 g of a iron and sulfur containing compound is decomposed to give 2.233g of iron. What is the empirical formula?

Answer 30

Fe2S3