Kaplan MCAT General Chemistry Review полностью

An equivalent is a measure of capacity to react in a certain way. One equivalent is an amount of a chemical compound equal to one mole of hydrogen ions or hydroxide ions in acid-base reactions or one mole of electrons in redox chemistry. Gram equivalent weight is the mass in grams of a compound that will yield one equivalent of hydrogen ions, hydroxide ions, or electrons. Normality is the ratio of equivalents per liter.

Combination reactions occur when two or more reactants combine to form one product.

Decomposition reactions occur when one reactant is chemically broken down into two or more products, usually by heat or electrolysis.

Single-displacement reactions occur when an atom or ion of one compound is replaced by an atom or ion of another element.

Double-displacement reactions occur when elements from two different compounds trade places with each other to form two new compounds. Neutralization reactions are a specific type of double displacement in which an acid reacts with a base to produce a solution of salt and water.

Net ionic equations ignore spectator ions to focus only on the species that actually participate in the reaction.

The steps for balancing chemical equations are as follows:

—Balance the nonhydrogen and nonoxygen atoms.

—Balance the oxygens.

—Balance the hydrogens.

—Balance charge if necessary.

Balanced reactions are essential for calculating limiting reactant (the reactant that will be consumed first in a chemical reaction) and yields. Theoretical yield is the maximum amount of product that can be formed, assuming all limiting reactant is consumed. Actual yield is the amount of product collected from a chemical reaction. Percent yield is the ratio of actual yield divided by theoretical yield, multiplied by 100 percent.

EQUATIONS TO REMEMBER

Practice Questions

1. Which of the following best describes ionic compounds?

A. Ionic compounds are formed from molecules containing two or more atoms.

B. Ionic compounds are formed of charged particles and are measured by molecular weight.

C. Ionic compounds are formed of charged particles that share electrons equally.

D. Ionic compounds are three-dimensional arrays of charged particles.

2. Which of the following has a formula weight between 74 and 75 grams per mole?

A. KCl

B. C₄H₁₀O

C. [LiCl]₂

D. BF₃

3. Which of the following is the gram equivalent weight of H₂SO₄?

A. 98.08 g/mol

B. 49.04 g/mol

C. 196.2 g/mol

D. 147.1 g/mol

4. Which of the following molecules CANNOT be expressed by the empirical formula CH?

A. Benzene

B. Ethyne

C.

D.

5. In which of the following compounds is the percent composition of carbon closest to 63 percent?

A. Acetone

B. Ethanol

C. C₃H₈

D. Methanol

6. What is the most accurate characterization of the reaction shown?

Ca(OH)₂ (aq) + H₂SO₄ (aq) CaSO₄ (aq) + H₂O ()

A. Single-displacement

B. Neutralization

C. Double-displacement

D. Redox

7. In the reaction shown, if 39.03 g of Na₂S are reacted with 113.3 g of AgNO₃, how much, if any, of either reagent will be left over once the reaction has gone to completion?

Na₂S + 2 AgNO₃ Ag₂S + 2 NaNO₃

A. 41.37 g AgNO₃

B. 13.00 g Na₂S

C. 26.00 g Na₂S

D. 74.27 g AgNO₃

8. Using a given mass of KClO₃, how would one calculate the mass of oxygen produced in the following reaction, assuming it goes to completion?

2 KClO₃ 2 KCl + 3 O₂

9. Aluminum metal can be used to remove tarnish from silver when the two solid metals are placed in water, according to the following reaction.

3 AgO + 2 Al 3 Ag + Al₂O₃

This reaction is a

I. double-displacement reaction.

II. single-displacement reaction.

III. redox reaction.

IV. combination reaction.

A. II only

B. I and III

C. II and III

D. IV only

10. Which of the following type(s) of reaction(s) generally has/have the same number of reactants and products?

I. Single-displacement reaction

II. Double-displacement reaction

III. Combination reaction

A. I only

B. II only

C. II and III

D. I and II

11. Which of the following is the correct net ionic reaction for the reaction of copper with silver nitrate?

A. Cu + AgNO₃ Cu(NO₃)₂ + Ag

B. Cu + 2 Ag⁺ + NO₃- Cu²⁺ + 2 NO₃- + 2 Ag⁺

C. 2 Ag⁺ + 2 NO₃- 2 NO₃- + 2 Ag⁺

D. Cu + 2 Ag⁺ Cu²⁺ + 2 Ag

12. In the process of photosynthesis, carbon dioxide and water combine with energy to form glucose and oxygen, according to the following equation.

CO₂ + H₂O + Energy C₆H₁₂O₆ + O₂

What is the theoretical yield, in grams, of glucose if 30.00 grams of water are reacted with excess carbon dioxide and energy, in the balanced equation?

A. 50.02 grams glucose

B. 300.1 grams glucose

C. 30.03 grams glucose

D. 1,801 grams glucose

13. One way to test for the presence of iron in solution is by adding potassium thiocyanate to the solution. The product when this reagent reacts with iron is FeSCN²⁺, which creates a dark red color in solution via the following net ionic equation.

Fe³⁺ (aq) + SCN^- FeSCN²⁺

How many grams of iron sulfate would be needed to produce 2 moles of FeSCN²⁺?

A. 400 grams

B. 800 grams

C. 200 grams

D. 500 grams