Chem Exam #4

A 20.0 mL solution of NaOH is neutralized with 47.2 mL of 0.200 M HBr. What is the concentration of the original NaOH solution?

0.472 M

A 15.0 mL solution of Sr(OH)₂ is neutralized with 52.6 mL of 0.350 M HCl. What is the concentration of the original Sr(OH)₂ solution?

0.614 M

In the following chemical reaction, which element is the oxidizing agent? 3 Sn(NO₃)₂(aq) + 2 Fe(s) → 2 Fe(NO₃)₃(aq) + 3 Sn(s)

Sn -Oxidizing agents gain electrons and are reduced. In this reaction, Sn²⁺ gains two electrons to become Sn

The products of a strong acid/strong base reaction are

When a strong acid is added to a strong base, the products of the reaction are water and a salt.

What is the oxidation number of each oxygen atom in HOOH?

-1 -Hydrogen has an oxidation number of +1 when not in its elemental state. Multiply the number of hydrogen by its oxidation number. Add the oxidation numbers of all atoms together and set equal to the charge on the molecule, which is zero. The oxidation number of oxygen can then be calculated. 2×O+(2×(+1))=0 O=-1

What is surface tension

-energy needed to separate the molecules at the surface of a liquid -As attractive forces increase, surface tension increases

Food value for fats

9 Cal/g= 9kcal/g

What is the chemical reaction combination?

A+B--> AB

What is the chemical reaction single displacement?

A+BC--> B+AC

What is the chemical reaction double displacement?

AB+CD--> AD + BC

What is the chemical reaction decomposition?

AB--> A+B

What is the formula for percent yield?

Actual yield/ theoretical yield x 100

What are the oxidation number assignment rules?

1. O.N. = 0 for atoms in pure elements 2. O.N.= the charge of monatomic ions 3. O.N. of fluorine= -1 in all of its compounds 4. O.N. of oxygen= -2 in nearly all its compounds. Exceptions: fluorine, H2O2, and KO2 5. O.N. of hydrogen= +1 in nearly all of its compounds. Exceptions: LiH (O.N.= -1) 6. O.N. values of the atoms in a neutral molecule sum to zero 7. O.N. values of the atoms in a polyatomic ion sum to the charge on the ion

How many milliliters of 0.20 M HCl is required to neutralize 70.0 mL of 0.80 M NaOH?

2.8 × 10² mL

The oxidation number on the nitrogen in NO₂ is

4 -Oxygen has an oxidation number of -2 when not in its elemental state. Multiply the number of oxygen by its oxidation number. Add the oxidation numbers of all atoms together and set equal to the charge on the molecule, which is zero. The oxidation number of nitrogen can then be calculated. N+ (2X(-2))=0 N=+4

Food value for carbs

4 Cal/g = 4 kcal/g

Food value for protein

4 Cal/g = 4 kcal/g

The oxidation number on the nitrogen in NO₃⁻ is

5 -Oxygen has an oxidation number of -2 when not in its elemental state. Multiply the number of oxygen atoms by its oxidation number. Add the oxidation numbers of all atoms together and set equal to the charge on the ion, which is -1. The oxidation number of nitrogen can then be calculated. N+(3×(−2))=−1 N=+5

The oxidation number on the phosphorus in Na₃PO₄ is

5 -Oxygen has an oxidation number of -2 when not in its elemental state. Multiply the number of oxygen atoms by its oxidation number. Sodium has an oxidation number of +1 when not in its elemental state. Multiply the number of sodium atoms by its oxidation number. Add the oxidation numbers of all atoms together and set equal to the charge on the molecule, which is zero. The oxidation number of phosphorus can then be calculated. P+(4×(−2))+(3×(+1))=0 P= +5

In the following chemical reaction, which element is the reducing agent? 2 Ag(s) + 2Cl⁻(aq) + 2 H₂O(l) → 2 AgCl(s) + H₂(g) + 2 OH⁻(aq)

Ag -Reducing agents lose electrons and are oxidized. In this reaction, Ag loses one electron to become Ag⁺.

In the following reaction, which element in what species is oxidized? C₂H₄ (g) + 3 O₂ (g) → 2 CO₂ (g) + 2 H₂O (g)

C in C₂H₄ -Reducing agents lose electrons and are oxidized. In this reaction, the oxidation number of carbon goes from +2 in C₂H₄ to +4 in CO₂.

Which one of the following can be classified as a nonelectrolyte?

CI₂ -An electrolyte is a substance that can dissolve in water to form ions. CI₂ does not ionize in water because it is a covalent molecular compound.

Consider the reaction below. Which species is(are) the Brønsted-Lowry base(s)? HCO₃⁻ (aq) + F⁻ (aq) ⇌ CO₃²⁻ (aq) + HF (aq)

CO₃⁻, F⁻ -Brønsted-Lowry bases accept protons and Brønsted-Lowry acids donate protons. In the forward reaction, the Brønsted-Lowry base is F⁻. In the reverse reaction, the Brønsted-Lowry base is CO₃²⁻.

In which one of the following molecules does chlorine have the highest oxidation number?

ClO₄⁻ -Oxygen has an oxidation number of -2 when not in its elemental state. Multiply the number of oxygen by its oxidation number. Then account for the charge of the molecule, which is -1. The oxidation number of the chlorine atom in ClO₄⁻ can then be calculated to show that ClO₄⁻ is the chlorine with the highest oxidation number. Cl+(4×(−2))=−1 Cl=+7

Which one of the following statements is correct about the reaction below? Mg(s) + 2 HCl(aq) → MgCl₂(s) + H₂(g)

H is the oxidizing agent because it gains electrons. -Oxidizing agents gain electrons and are reduced. Reducing agents lose electrons and are oxidized. In this reaction, Mg loses two electrons to become Mg²⁺. Two H⁺ each gain one electron to become H₂

Which one of the following can be classified as a weak electrolyte?

HF -Weak electrolytes ionize when dissolved in water but not completely. Weak acids and bases are weak electrolytes and HF is a weak acid. Therefore, HF is a weak electrolyte.

Consider the reaction below. Which species is(are) the Brønsted-Lowry acid(s)? HF (aq) + NH₃ (aq) ⇌ NH₄⁺ (aq) + F⁻ (aq)

HF, NH₄⁺ -Brønsted-Lowry bases accept protons and Brønsted-Lowry acids donate protons. In the forward reaction, the Brønsted-Lowry acid is HF. In the reverse reaction, the Brønsted-Lowry acid is NH₄⁺.

Which one of the following is NOT a strong electrolyte?

HNO₂ -Strong electrolytes completely dissociate in water. They can be in the form of salts, strong acids, or strong bases. HNO₂ dissociates in water but not completely and is a weak acid. It is a weak electrolyte.

What is a cohesive force?

Interactions between like particles -Ex: mercury to mercury

Consider the following reaction: Mg²⁺(aq) + Cu(s) → Cu²⁺(aq) + Mg(s). In this reaction, Mg²⁺(aq) is:

Oxidized and reduced -Oxidizing agents gain electrons and are reduced. Reducing agents lose electrons and are oxidized. In this reaction, Mg²⁺ gains two electrons when it becomes Mg.

Which acid-base definition classifies an acid as an electron-pair acceptor?

Lewis -Lewis acids accept electron-pairs and Lewis bases donate electron pairs.

In the following reaction, which element in what species is oxidized? Au(NO₃)₃ (aq) + 3 Li(s) → Au(s) + 3 LiNO₃ (aq)

Li -Reducing agents lose electrons and are oxidized. In this reaction, Li loses an electron to form Li⁺.

Strong bases

LiOH NaOH KOH RbOH CsOH Ca(OH)2 Sr(OH)2 Ba(OH)2

What is the critical point in a phase diagram?

Liquid and gas phases have the same density

Which one of the following can be classified as a strong electrolyte?

NH₄NO₃ -NH₄NO₃ dissolves in water and completely dissociates into ammonium ions and nitrate ions. Therefore it is classified as a strong electrolyte.

In the following chemical reaction, which element is the oxidizing agent? CH₄(g) + 2 O₂(g) → CO₂(g) + 2H₂O(g)

O -Oxidizing agents gain electrons and are reduced. In this reaction, O gains two electrons to become O²⁻.

What is an adhesive force?

interactions between unlike particles -Ex: water to glass

HI is an Arrhenius acid because

it produces hydronium ions in solution -Arrhenius acids produce hydronium ions when dissociated in water.

what is the formula for percent composition?

mass of element in compound/mass of compound x 100

A nonelectrolyte will

not form any ions in aqueous solution