Deck 3: Chemical Reactions

Question 1

Define molecular mass and formula mass. How are they calculated?

Answer 1

The molecular mass of a substance is the sum of the average masses of the atoms in one molecule of a substance. It is calculated by adding together the atomic masses of the elements in the substance, each multiplied by its subscript (written or implied) in the molecular formula. Because the units of atomic mass are atomic mass units, the units of molecular mass are also atomic mass units. Unlike molecules, which have covalent bonds, ionic compounds do not have a readily identifiable molecular unit. So for ionic compounds we use the formula mass (also called the empirical formula mass) of the compound rather than the molecular mass. The formula mass is the sum of the atomic masses of all the elements in the empirical formula, each multiplied by its subscript (written or implied). It is directly analogous to the molecular mass of a covalent compound. Once again, the units are atomic mass units.

Question 2

How many molecules are present in 300.0 g of benzaldehyde (C₆H₅CHO)?

A) 2.836 × 10²³ molecules
B) 1.702 × 10²⁴ molecules
C) 2.836 × 10²³ molecules
D) 6.023 × 10²⁴ molecules
E) 3.011 × 10²³ molecules

Answer 2

1.702 × 10²⁴ molecules

Question 3

What is the mass of oxygen in 1 g of glutamine (C₅H₁₀N₂O₃)?

A) 0.114 g
B) 0.411 g
C) 0.786 g
D) 0.328 g
E) 0.823 g

Answer 3

0.328 g

Question 4

The empirical formula for a compound can be determined using only its percentage composition.

Question 5

The mass number of an atom is approximately equal to the numerical value of the atom's atomic mass.

Question 6

_____ are the units assigned to mass number.

Question 7

The _____ of a substance is the sum of the average masses of the atoms in one molecule of a substance.

Question 8

The empirical formula of a substance gives only the relative numbers of atoms in the substance in the smallest possible ratio.

Question 9

How many moles are present in 250 g of glucose (C₆H₁₂O₆)?

A) 25 moles
B) 1.4 moles
C) 6.0 moles
D) 180 moles
E) 8.5 moles

Question 10

What is the molecular mass of formaldehyde (CH₂O)?

A) 24.022 amu
B) 15.999 amu
C) 46.096 amu
D) 30.026 amu
E) 34.562 amu

Question 11

The mass percentage of oxygen in water is the same as the mass percentage of oxygen in potassium hydroxide.

Question 12

The empirical formula for toluene is C₇H₈.

Question 13

A mole of a substance contains _____ number of particles of that substance.
4. 12.011g of carbon will contain _____ of carbon.

Question 14

What is the mass percentage of nitrogen in glutamine (C₅H₁₀N₂O₃)?

A) 41.1 %
B) 6.90 %
C) 19.2 %
D) 32.8 %
E) 8.88 %

Question 15

What is the molar mass of a substance? How is the molar mass of an element and a compound calculated?
g. For an element, the molar mass is the mass of 1 mol of atoms of that element; for a covalent molecular compound, it is the mass of 1 mol of molecules of that compound; for an ionic compound, it is the mass of 1 mol of formula units. That is, the molar mass of a substance is the mass (in grams per mole) of 6.022×10²³ atoms, molecules, or formula units of that substance. In each case, the number of grams in 1 mol is the same as the number of atomic mass units that describe the atomic mass, the molecular mass, or the formula mass, respectively.

Question 16

The law of definite proportions states that a chemical compound always contains the same proportion of elements by mass.

Question 17

The mass number of water is approximately equal to 18.

Question 18

What is the mass of 3.65 moles of sodium bicarbonate?

A) 307 g
B) 486 g
C) 84.0 g
D) 106 g
E) 87.8 g

Question 19

What is the mass percentage of carbon in glutamine (C₅H₁₀N₂O₃)?

A) 41.1 %
B) 6.90 %
C) 19.2 %
D) 32.8 %
E) 8.88 %

Question 20

If the molar mass of the compound is known, its molecular formula can be determined from the empirical formula.

Question 21

The mass percentage of oxygen in benzaldehyde is _____.

Question 22

What is the mass of carbon contained in 245 g of sucrose (C₁₂H₂₂O₁₁)?

A) 245 g
B) 131 g
C) 103 g
D) 201 g
E) 13.1 g

Question 23

The equation for the formation of fluorapatite, a crystal precursor during the production of phosphorus, is as follows: xCa₃(PO₄)₂ + CaF₂ → 2Ca₅(PO₄)₃F. If the above chemical equation is balanced, what would the value of x be?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 24

The law of definite proportions states that the percentage of each element present in a pure substance is _____.

Question 25

The equation H₂O $\rightarrow$ H₂ + O₂ is balanced.

Question 26

One gram of a substance containing hydrogen, carbon, and oxygen during combustion analysis produces 1.4656 g of CO₂ and 0.6000g of H₂O. If the molar mass of the compound is 180 g/mol then what is the molecular formula of the compound?

A) CH₂O
B) C₂H₄O
C) C₄H₈O₄
D) C₅H₁₀O₁₀
E) C₆H₁₂O₆

Question 27

How many molecules of calcium will react with 4.00 moles of ZnSO₄ according to the balanced chemical equation: Ca + ZnSO₄ → CaSO₄ + Zn?

A) 4.00 moles
B) 1.204 ×10²⁵ moles
C) 1.00 moles
D) 3.92 ×10²⁵ moles
E) 2.41 ×10²⁴ moles

Question 28

Sucrose is fermented by microorganisms into ethanol as seen in the reaction: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. In the above balanced chemical equation, how many grams of ethanol are produced from 2.00 moles of sucrose?

A) 46.1 g
B) 184 g
C) 342 g
D) 44.0 g
E) 92.1 g

Question 29

The mole ratio of carbon dioxide to water in the equation CH₄ +2O₂ $\rightarrow$ CO₂ + 2H₂O is 1:2.

Question 30

To determine the molecular weight of a compound from its empirical formula one needs the compound's _____.

Question 31

The balanced equation for aluminum hydroxide and formic acid reacting to produce aluminum formate and water is:

A) 3Al(OH)₃ + 3HCOOH $\rightarrow$ 3Al(HCOO)₃ + 3H₂O .
B) Al(OH)₃ + HCOOH $\rightarrow$ Al(HCOO)₃ + H₂O.
C) Al(OH)₃ + 2HCOOH $\rightarrow$ Al(HCOO)₃ + 2H₂O.
D) 2Al(OH)₃ + HCOOH $\rightarrow$ Al(HCOO)₃ + H₂O.
E) Al(OH)₃ + 3HCOOH $\rightarrow$ Al(HCOO)₃ + 3H₂O.

Question 32

One gram of a substance containing hydrogen, oxygen, and carbon on combustion produces 1.4656 g of CO₂ and 0.6000g of H₂O. What is the empirical formula of this compound?

A) CHO
B) CH₂O₂
C) CHO₄
D) CH₂O
E) C₂HO

Question 33

The coefficient of oxygen in the unbalanced equation P₄ + O₂ $\rightarrow$ P₂O₃ after balancing is 5.

Question 34

The empirical formula expresses the relative numbers of atoms in an element in the _____.

Question 35

What qualitative and quantitative information can one understand from a balanced chemical equation?

Question 36

In a balanced chemical equation the number and type of atoms on both sides need not be the same.

Question 37

In the equation NaOH(s) + HCl(aq) $\rightarrow$ NaCl(aq), the term aq. in "parentheses" indicates that HCl is _____.

A) a solid
B) unreactive
C) a liquid
D) in water
E) present in large amounts

Question 38

For the equation PCl₅ + H₂O → POCl₃ + HCl to be balanced:

A) two should be added as the coefficient of PCl₅.
B) four should be added as the coefficient of H₂O.
C) HCl must be replaced with Cl₂ and H₂.
D) two should be added as the coefficient of H₂O.
E) two should be added as the coefficient of HCl.

Question 39

The balanced equation for aluminum reacting with chlorine is:

A) Al + Cl₂ $\rightarrow$ AlCl₃.
B) 3Al + 2Cl₂ $\rightarrow$ 3AlCl₃.
C) Al + Cl₂ $\rightarrow$ 2AlCl₃.
D) 2Al + 3Cl₂ $\rightarrow$ 2AlCl₃.
E) 2Al + Cl₂ $\rightarrow$ AlCl₃.

Question 40

What is combustion analysis and how is it carried out?

Question 41

Zn(s) + _____ AgNO₃(aq) → Zn(NO₃)₂(aq) + 2Ag

Question 42

Acetyl salicylic acid commonly known as Aspirin. It is prepared by the reaction of salicylic acid and acetic anhydride (as shown below). C₇H₇O₃(l) + C₄H₆O₃(l)  C₉H₈O₄(s) + C₂H₄O₂(l) + H⁺(aq)
Salicylic acid acetic anhydride acetyl salicylic acid acetic acid
If 10 ml of salicylic acid (1.443 g/mL) reacts with 15 ml of acetic anhydride (1.082 g/mL), the limiting reagent is _____.

A) water
B) acetic anhydride
C) acetic acid
D) acetyl salicylic acid
E) salicylic acid

Question 43

Write a short note on limiting reactants. Explain a method to determine the yield of the product, when the quantities of reactants are given.

Question 44

Methane combusts to form water and carbon dioxide. If the percentage yield for water in this reaction is 95.0%, what is the amount of water produced when 3.00 *10² g of methane is burnt?

A) 37.4 g
B) 375 g
C) 535 g
D) 641 g
E) 675 g

Question 45

The _____of a reaction is the ratio of the actual yield to the theoretical yield, expressed as a percentage.

Question 46

Stoichiometrically one mole of atomic oxygen will always react with _____ mole of molecular hydrogen to produce one mole of water.

Question 47

The ratio of the number of moles of one substance to the number of moles of another is called the_____.

Question 48

The rusting of iron is an oxidation-reduction reaction.

Question 49

Explain the steps involved when converting between masses of reactants and products.

Question 50

During the combustion of sodium in air, _____ is the reactant present in excess.

Question 51

Each step of a four-step reaction has a yield of 75.00%. What is the percent yield for the overall reaction?

A) 75.00%
B) 56.24%
C) 42.19%
D) 31.64%
E) 29.65%

Question 52

In a balanced chemical reaction the number of atoms, molecules, or formula units of a reactant or a product is indicated by the _____ of that species.

Question 53

One mole of NH₄OH will react with _____ molecules of HCl to form one mole of ammonium chloride and water.

Question 54

A(n) _____is the amount of product or reactant specified by the coefficients in a balanced chemical equation.

Question 55

_____ is the maximum amount of product(s) that can be obtained in a reaction from a given amount of reactant(s).

Question 56

The oxidation state of a copper atom in Cu₂SO₄ is +2.

Question 57

Acetyl salicylic acid commonly known as Aspirin. It is prepared by the reaction of salicylic acid and acetic anhydride (as shown below). C₇H₇O₃(l) + C₄H₆O₃(l)  C₉H₈O₄(s) + C₂H₄O₂(l) + H⁺(aq)
Salicylic acid acetic anhydride acetyl salicylic acid
If 10.0 ml of salicylic acid (1.443 g/mL) reacts with 15 mL of acetic anhydride (1.082 g/mL), then how many moles of acetyl salicylic acid would be produced?

A) 0.160 moles
B) 0.104 moles
C) 1.022 moles
D) 0.456 moles
E) 0.136 moles

Question 58

When a metal is oxidized it loses electrons to an oxidizing agent.

Question 59

To balance the equation given below, the coefficient of HNO₃ should be _____.
NaCl(aq) + HNO₃(aq) + O₂(g) → NaNO₃(aq) + Cl₂(g) + H₂O(l)

Question 60

Elaborate on the steps followed during the balancing of a chemical equation.

Question 61

The composition of the atmosphere is constant regardless of altitude or region.

Question 62

Molecular fluorine is a very powerful reducing agent.

Question 63

A(n) _____ is an oxidation-reduction reaction in which the oxidant is O₂.

Question 64

The reaction of an amine with a carboxylic acid is a variant of a condensation reaction.

Question 65

In the reaction Ca(OH)₂ + 2Na $\rightarrow$ 2NaOH +Ca, _____ is a reducing agent.

A) Ca(OH)₂
B) OH
C) Na
D) Ca
E) NaOH

Question 66

Which of the following is not an oxidation-reduction reaction?

A) Mg(s)+ 2HCl(l) $\rightarrow$ MgCl₂(s) + H₂(g)
B) Cl₂(aq)+ MgBr₂(s) $\rightarrow$ MgCl₂(s) + Br₂(aq)
C) NaOH(aq)+ HCl(aq) $\rightarrow$ NaCl(aq) + H₂O(l)
D) Pb(s) + PbO₂(s) + 2H₂SO₄(aq) $\rightarrow$ 2PbSO₄(s) + 2H₂O(l)
E) Cu(s) + H₂SO₄(l) $\rightarrow$ CuSO₄(aq) + H₂(g)

Question 67

Which of the following reactions is caused by ultraviolet light absorption in the upper layers of the atmosphere?

A) H₂O(g) $\rightarrow$ H₂(g) + O(g)
B) O(g) + O(g) $\rightarrow$ O₂(g)
C) 3O(g) $\rightarrow$ O₃(g)
D) H₂O(g) + O(g) $\rightarrow$ H₂O₂(g)
E) O₂(g) $\rightarrow$ 2O(g)

Question 68

What is the oxidation state of oxygen in ethyl alcohol?

A) +1
B) -1
C) +2
D) -2
E) 0

Question 69

Which of the following is a condensation reaction?

A) C₃H₆(g) + Cl₂(g) → ClCH₂CH₂CH₂Cl(g)
B) AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)
C) MgCO₃(s) → MgO(s) + CO₂(g)
D) H₂SO₄(l) + 2KOH(s) →K₂SO₄(aq) + H₂O(l)
E) K(s) + NaHCO₃(aq) → NaKCO₃(aq) + H₂

Question 70

During the rusting of iron in air, atmospheric oxygen is _____ by iron to form rust.

Question 71

Write a short note on catalysts used in chemical reactions.

Question 72

The lowest layer of the atmosphere is the ionosphere.

Question 73

During reduction an atom _____ electrons.

Question 74

Ultraviolet light is higher energy radiation that cannot be detected by the human eye and can cause a wide variety of chemical reactions that are harmful to organisms.

Question 75

What is the oxidation state of chlorine in ClF₃ given the fact that fluorine is more electronegative than chlorine?

A) -1
B) -2
C) +1
D) +2
E) +3

Question 76

What percent of the earth's atmosphere is comprised of oxygen?

A) 78.084%
B) 67.392%
C) 42.732%
D) 20.948%
E) 0.934%

Question 77

Write a note on the rules for assigning oxidation states.

Question 78

_____ are catalysts that occur naturally in living organisms and catalyze biological reactions.

Question 79

In the reaction Mg + 2HCl $\rightarrow$ MgCl₂ + H₂, _____ is the oxidizing agent.

A) H₂
B) Cl₂
C) Mg
D) HCl
E) MgCl₂

Question 80

The component of the atmosphere present in the greatest quantity is nitrogen.