Review Sheet for Ap Chemistry Essay Example
Review Sheet for Ap Chemistry Essay Example

Review Sheet for Ap Chemistry Essay Example

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  • Pages: 15 (3910 words)
  • Published: September 2, 2016
  • Type: Paper
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The answer to the question should be written in the provided space or on a separate sheet of paper, while maintaining the text alignment justification.

The distinction between qualitative and quantitative measurements lies in the type of results they provide. Qualitative measurements yield descriptive outcomes, while quantitative measurements yield precise, usually numerical results. For instance, stating "The rock is heavy" is a qualitative measurement, whereas stating "The rock weighs 110 grams" is a quantitative measurement. This differentiation is relevant to the field of Scientific Measurement.

2) The distinction between precision and accuracy should be explained. Consider three different measurements of a sugar sample with a known mass of 1 g. How can the accuracy of the measurements be determined? How can their precision be determined? Is it possible


for the three measurements to be precise but not accurate? Clarification is required. Answer: Precision pertains to the consistency of a measurement under identical conditions, while accuracy refers to how closely a measurement aligns with the true value of what is being measured. If the three measurements are close in value, they exhibit precision; if they closely match the actual 1-g mass of the sample, they demonstrate accuracy. Regardless of their closeness to the true value, if the measurements are very similar, they are precise. Hence, it is possible for the measurements to be precise but not accurate. Topic: Scientific Measurement

3) The rules for determining the number of significant figures in the results of addition, subtraction, multiplication, and division are as follows:
- In addition or subtraction, the answer cannot have more digits to the right of the decimal point than th

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measurement with the least number of digits to the right of the decimal point.
- In multiplication or division, the answer cannot have more significant figures than the measurement with the least number of significant figures. The position of the decimal point does not affect the number of significant figures.
Topic: Scientific Measurement

4) The metric system is the preferred system of measurement for science because it is based on units that are multiples of ten, simplifying conversions between units. Additionally, all necessary units can be derived from the seven basic units of the metric system. Topic: Scientific Measurement

The density of a metal is higher than that of water due to either heavier atoms or more closely packed atoms. This is reflected in scientific measurements.

6) The reason why the densities of most substances decrease with temperature is because their atoms or molecules tend to move farther apart, leading to an increase in volume. Although the mass remains constant, the resulting increase in volume causes a decrease in density (mass/volume). Topic: Scientific Measurement

7) The difference between specific gravity and density is as follows: Density is absolute and has units, depending only on temperature. On the other hand, specific gravity is a comparison of the density of a substance to the density of a reference substance, usually at the same temperature. For example, the density of aluminum at 25°C is 2.76 g/cm3, while the specific gravity of aluminum at 25°C, using water at 4°C as the reference standard, is simply 2.70. This topic falls under Scientific Measurement.

8) The difference between the Celsius and Kelvin temperature scales can be explained

as follows. Both scales utilize the freezing and boiling points of water as reference temperature values. The Celsius scale sets the freezing point of water as O°C and the boiling point as 100°C, dividing the region between these two points into equal degree intervals. On the other hand, the Kelvin scale designates 0 K as the temperature at which an ideal gas would have zero volume, known as absolute zero. This is considered the lowest theoretically attainable temperature. Absolute zero corresponds to -273°C on the Celsius scale. While both scales utilize degree intervals of equal size, their difference lies in how the zero point is determined. The Celsius scale sets the zero point at the freezing point of water, while the Kelvin scale sets it at the point where an ideal gas would theoretically have zero volume. These scales are related by the formulas K = 0°C + 273 or 0°C = K - 273.

9) The terms molecular formula and formula unit can be explained as follows. A molecular formula represents the types and quantities of atoms found in a compound's molecule. An example of a molecular formula is CO2. On the other hand, a formula unit refers to the simplest whole-number ratio of ions present in an ionic compound. An example of a formula unit is BaCl2 with a barium to chloride ion ratio of 1:2. Unlike a molecule, BaCl2 is not considered one. Topic: Chemical Name ; Formula

10) Chemists developed a system for naming chemical compounds because common names do not provide information about the compound's chemical composition. While common names may indicate physical or chemical properties, they typically

do not reveal the elements present in the compound. The systematic naming method not only identifies the atoms in the compound but also indicates their ratio of combination. By using this method, scientists worldwide can determine the components and their relative quantities within a compound. Topic: Chemical Name & Formula

11) The characteristics of ionic and molecular compounds can be compared. Ionic compounds consist of oppositely charged ions, while molecular compounds consist of molecules. Ionic compounds are made up of metallic and nonmetallic elements, whereas molecular compounds are composed solely of nonmetallic elements. Ionic compounds have high melting points and are solid in nature. On the other hand, molecular compounds can exist as solids, liquids, or gases at room temperature and possess low melting points. The topic discussed here is Chemical Name & Formula.

12) To write an ionic formula, start with the cation followed by the anion. It is important to ensure that the resulting formula represents a neutral substance. The charge of the anion becomes the subscript of the cation, while the charge of the cation becomes the subscript of the anion. When the charges of both ions are equal, no subscripts need to be written. For example, for copper(I) phosphate, the formula is Cu3PO4. For copper(II) phosphate, the formula is Cu3(PO4)2. This concept falls under the topic of Chemical Name & Formula, and there are many other potential examples.

13) The compounds CuBr2, SCl2, and BaF2 have names such as copper(II) bromide, sulfur dichloride, and barium fluoride. The use or omission of the Roman numeral (II) and the prefix di- is explained by the fact that copper is a

transition element. For sulfur, prefixes are used because it is a nonmetal. However, for barium, neither a Roman numeral nor a prefix is necessary as it is a Group A metal. This topic relates to Chemical Name & Formula.

14) The advantage of using the specific term "gram molecular mass" instead of the general term "gram formula mass" is that it avoids confusion when dealing with diatomic gases like nitrogen and oxygen. For example, nitrogen has a gram molecular mass of 28 g, whereas the gram formula mass could be either 14 g or 28 g depending on whether we are referring to nitrogen atoms or nitrogen molecules. This is particularly relevant in the context of unit conversion.

15) It is possible to calculate the density of a gas at STP by knowing only its gram formula mass. However, the same calculation cannot be made for a solid or a liquid. The reason for this is that the molar volume of any gas is 22.4 L at STP. The density of the gas can be calculated using the formula: x = density of gas (g/L). On the other hand, the molar volumes of different solids and liquids are not consistently the same under any given condition.

The factor that determines if one metal will replace another metal in a compound during a single-replacement reaction is the relative reactivity of the two metals. The activity series of metals provides a list of metals in order of decreasing reactivity. In this series, a highly reactive metal can replace any metal that is positioned lower in the series. This concept is relevant to the topic

of Chemical Reactions.

17) The coefficients in a balanced chemical reaction are important because they show the relative number of moles of reactants and products. This information allows for the calculation of the amounts of reactants and products. The number of moles can be converted to mass, volume, or the number of representative particles. This is relevant to the topic of stoichiometry.

18) The type of stoichiometric calculation where the conversion to and from moles can be skipped is volume-volume conversions between gases. This is possible because all gases at STP have the same molar volumes. The coefficients in a balanced equation provide information on both the relative number of moles and the relative volumes of the gases involved in the reaction. Topic: Unit Conversion

The kinetic theory relies on three fundamental assumptions. Firstly, it assumes that a gas consists of particles. Secondly, it assumes that these particles are constantly moving in a random manner. Lastly, it assumes that all collisions between the particles are elastic. This topic is related to matter and intermolecular forces (IMF).

20) The pressure exerted by a gas remains unaffected by the size of its particles because gas particles at the same temperature possess the same average kinetic energy. When a consistent number of particles with equal average kinetic energy are contained within an equal amount of space, they will exert an equivalent pressure, irrespective of their size. It is important to note that the particles of a gas are widely spaced with only empty space between them. Regardless of the particle size, they are still relatively small in comparison to the volume of space

occupied by the gas. Topic: Matter- IMF

21) The reason why a liquid will completely evaporate if kept at a constant temperature below its boiling point is because the particles in the liquid have different energy levels. Some particles in the liquid have enough energy to overcome the attractive forces at the surface and turn into vapor. While these high-energy particles leave, the temperature of the liquid would normally decrease. However, when the liquid is exposed to the environment, it absorbs heat from the surroundings to keep a steady temperature. This causes more particles in the liquid to gain sufficient energy to escape into vapor. This process of escaping, absorbing heat, and further escaping continues until the liquid has evaporated entirely. Topic: Matter- IMF

22) The water molecule is a simple, triatomic molecule with a polar structure. The covalent bonds between the oxygen (O) and hydrogen (H) atoms in water are highly polar, as the oxygen atom has a greater electronegativity than hydrogen. This leads to the oxygen atom acquiring a slightly negative charge, while the hydrogen atoms acquire a slightly positive charge. The atoms in the water molecule are connected at a 105° angle, which results in the charges on the individual atoms not canceling each other out. Therefore, the water molecule itself is polar, with a slight negative charge around the oxygen and a slight positive charge around the hydrogens. This polarity allows water molecules to attract each other.

The hydrogen of one molecule forms a stronger attraction with the oxygen of another molecule, known as hydrogen-bonding. This type of bonding is stronger than other polar attractions because the

hydrogen nucleus lacks the protection of an electron cloud due to having only 1 electron. The strong intermolecular attraction resulting from hydrogen-bonding is responsible for numerous unique properties of water, such as high surface tension, low vapor pressure, high specific heat, high heat of vaporization, and high boiling point. Topic: Aqueous Stoichiometry

Why will a needle float on the surface of water but sink immediately if it breaks through the surface? The surface of the water presents greater resistance (surface tension) to the needle than does the rest of the water. This is because water molecules are packed more closely at the surface than elsewhere. This closer packing results from the one-sided intermolecular attraction that exists at the surface of the water. The water molecules at the surface are attracted to the water molecules below them. But, unlike in the rest of the liquid, there are no water molecules above them to pull them in the opposite direction. The closer-packed water molecules at the surface form a "skin" that is denser than the water below. Objects denser than water (e.g. the needle) can float upon this skin. All liquids will exhibit surface tension, but this phenomenon is more pronounced in water because of its hydrogen-bonding.

Topic: Aqueous Stoichiometry

24) The high heat capacity of water is related to its ability to moderate temperature changes in large bodies of water. This is because water can absorb and release significant amounts of energy with only small changes in temperature. As a result, temperature changes in the vicinity of large bodies of water are moderated. When the surroundings become warmer, water absorbs heat energy but its

temperature increases only slightly. This helps to regulate the temperature in the area surrounding the water. Similarly, in cold weather, water gives off energy to the surroundings but its temperature decreases only slightly. Hence, bodies of water also moderate cold temperatures in nearby areas. Topic: Aqueous Stoichiometry

25) Water has a relatively high heat of vaporization due to its hydrogen-bonding. This extensive network of hydrogen-bonds holds the water molecules together tightly compared to other liquids. The vaporization of water requires overcoming the attractive force of these hydrogen-bonds. Topic: Aqueous Stoichiometry

Ice is less dense than water because its structure consists of a regular, open framework where water molecules are more spaced out compared to liquid water. When ice melts, this structure collapses and the water molecules become closer together, causing the water to become denser than the ice. This phenomenon relates to the topic of Aqueous Stoichiometry.

27) The terms solute, solvent, and aqueous solution are defined as follows. A solute refers to the dissolved material in a solution, while a solvent is the dissolving medium in a solution. An aqueous solution, on the other hand, is any sample of water that contains one or more dissolved substances. An example of an aqueous solution is salt (NaCl) in water. In this particular solution, water functions as the solvent and salt serves as the solute. This topic pertains to Aqueous Stoichiometry.

28) The process of solvation involves solvent molecules colliding with solute particles and exerting attractive forces on them. When these forces are stronger than the attractive forces within the solute, the solute particles separate from the rest of the solute.

Then, the solute particles are surrounded by solvent particles. Topic: Aqueous Stoichiometry

29) An electrolyte refers to a substance that has the ability to conduct an electric current either in an aqueous solution or when in a molten state. Strong electrolytes are substances that are completely, or almost completely, ionized when dissolved in water. Examples of strong electrolytes include sodium chloride, hydrochloric acid, and sodium hydroxide. On the other hand, weak electrolytes only undergo slight ionization when dissolved in water. Examples of weak electrolytes are mercuric chloride and acetic acid. This information is relevant to the topic of Aqueous Stoichiometry.

The text below explains the differences between efflorescent, hygroscopic, and deliquescent substances and provides examples:

Efflorescent substances are hydrates that release their water of hydration spontaneously. If a hydrate has a higher water vapor pressure than the water vapor in the air, it will effloresce. CuSO4 • 5H20 (copper sulfate pentahydrate) is an example of an efflorescent compound.

Hygroscopic substances, on the other hand, are substances that absorb moisture from the air and form hydrates or solutions.

Hygroscopic substances, such as phosphorus pentoxide (P 2O5), sodium hydroxide (NaOH), and calcium chloride monohydrate (CaCl 2 • H20), have the ability to absorb moisture from the air. On the other hand, deliquescent substances completely dissolve in the absorbed water due to their high moisture absorption capacity. When deliquescent substances absorb water, the water vapor pressure of the resulting solution is lower than that of the water vapor in the air. Sodium hydroxide serves as an example of a deliquescent substance. This topic relates to Aqueous Stoichiometry.

31) The distinction between a suspension, a colloid,

and a solution lies in their particle sizes. Suspensions are heterogeneous mixtures where particles settle upon standing. These particles have an average diameter greater than Colloids, on the other hand, contain particles of intermediate size between suspensions and true solutions.
An example of a suspension is a sand-water mixture.

The average diameter of a particle in colloidal suspension ranges from 1 nm to 100 nm, displaying the Tyndall effect. This effect occurs when light is scattered in all directions by the particles in the suspension. It is important to note that solutions do not exhibit the Tyndall effect, as they are homogeneous mixtures with particles of an average diameter of 1 nm. The topic being discussed is Aqueous Stoichiometry.

32) Regarding saturated solutions, they contain the highest possible quantity of solute for a particular quantity of solvent at a consistent temperature. To illustrate, in 100 g of water, only a maximum of 36.2 g of sodium chloride can dissolve. Beyond this level of concentration, there exists a dynamic balance between the solid solute and its dissolved ions. Within this equilibrium, an equal number of ions are leaving and entering the solution over time, which results in the continual presence of solid substance. The subject matter being discussed is solutions.

33) In discussing the factors that can affect the solubility of a substance, it is important to consider temperature, pressure, and the nature of the substances involved. For instance, sodium chloride has greater solubility in water when the temperature is high compared to when it is low. On the other hand, gases exhibit lower solubility at higher temperatures and higher solubility at lower temperatures.

When dealing with a gas, its solubility in a solution increases as the partial pressure of the gas increases. Another example is the difference in solubility between sodium nitrate and barium sulfate; sodium nitrate is significantly more soluble in water regardless of temperature. In general, polar substances are more likely to dissolve in water while nonpolar substances tend to be insoluble. This discussion revolves around the topic of solutions.

Supersaturation is the topic of discussion in question 34. It refers to a solution that holds more solute than it can theoretically accommodate at a specific temperature. In a supersaturated solution, there is no dynamic equilibrium between solid and dissolved particles due to the absence of solid. Crystallization in such a solution can be initiated by introducing a seed crystal or by exposing the solution to a rough surface. The latter method involves scratching the inside of the container that holds the solution. The overall topic under consideration is "Solution".

35) The effect of a solute on the boiling point, freezing point, and vapor pressure of the solvent can be explained on a particle basis. Boiling point elevation, freezing point lowering, and vapor pressure lowering are colligative properties, meaning they depend on the number of particles in solution rather than the chemical nature of the solute or solvent. Boiling point elevation occurs because additional attractive forces exist between solute and solvent, which need to be overcome for the solution to boil. To overcome these forces, kinetic energy must be added. Freezing point lowering happens because more kinetic energy needs to be withdrawn from the solution due to the solute being surrounded by shells of

solvent. This interferes with the formation of the orderly pattern that particles assume during solidification. Vapor pressure lowering occurs because the formation of solvent shells around solute particles reduces the number of solvent particles with sufficient kinetic energy to vaporize. This explanation pertains to the topic of solutions.

The effects of reactant concentration and particle size on the rate of a reaction can be explained as follows. When the particle size is small, it enhances the reaction rate due to the increased surface area per mass of particles, allowing for more collisions to occur per second. Similarly, a high concentration of reactants leads to an increased reaction rate because there are more molecules available to collide with each other every second. This phenomenon is discussed in the context of kinetics.The effect of a catalyst on the rate of a reaction is that it increases the reaction rate by allowing the formation of a less energetic activated complex. An example of this is platinum, which acts as a catalyst for certain gas reactions. This topic falls under kinetics.

38) The reason why some reactions are reversible is because they have a slight change in free energy, allowing them to easily proceed in both directions. Most reactions demonstrate some level of reversibility.
Topic: Kinetics

The concept of free energy is connected to the spontaneity of a reaction. Free energy measures a reaction's capacity to perform work. Spontaneous reactions release free energy, while nonspontaneous reactions consume it. This concept is discussed in the topic of thermodynamics.

40) The reason why a reaction is spontaneous is because it can lead to a lower energy state or

a more disordered state for the system. An example of this is the reaction between sodium and water. In some cases, both the energy and the disorder increase, while in others, both decrease. For instance, the dissolution of ammonium nitrate is spontaneous even though it requires energy. This is because the increase in disorder outweighs the unfavorable increase in energy. Overall, this relates to the topic of thermodynamics.

41) Spontaneous reactions are known to produce the written products under specified conditions, while nonspontaneous reactions do not give products under those conditions. However, some spontaneous reactions may occur so slowly that they appear to be nonspontaneous. This topic falls under thermodynamics.

The question is, "What is entropy and what are some examples?"
The answer is: Entropy refers to the level of disorder in a system. Some examples of entropy include:
- A gas having more entropy compared to a liquid.
- An increase in entropy occurring due to a chemical reaction where there are more product molecules than reactant molecules.
- A solution of sodium chloride in water having more entropy than a sodium chloride crystal.
The topic is Thermodynamics.

43) Acid and bases have similar properties. They are both electrolytes that can cause indicators to change colors. Moreover, they can react with one another to create water and a salt. Acids have a sour taste, while bases have a bitter taste. Additionally, bases feel slippery. Acids can also react with certain metals to generate hydrogen gas. Topic: Acid – Base Equilibria

44) The procedure for measuring pH using a pH meter involves the following steps: first, wash the

electrodes with distilled water. Next, immerse the electrodes in a pH 7 buffer solution and calibrate the meter. Afterward, rinse the electrodes once more. Finally, measure the pH of the solution and store the electrodes in a distilled water solution. This topic pertains to Acid-Base Equilibria.

45) According to Arrhenius, acids are substances that give up a proton to water while bases are substances that give up a hydroxide ion in water. An example of an Arrhenius acid is hydrochloric acid, which gives up its proton when it dissolves in water. On the other hand, sodium hydroxide is an example of an Arrhenius base because it gives up its hydroxide ion as it dissolves in water. The topic being discussed is Acid – Base Equilibria.

According to the Bronsted-Lowry theory, acids are substances that donate protons to other substances while bases are substances that accept protons from other substances. For example, ammonia behaves as a Bronsted-Lowry base when it accepts a proton from water.

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