Chemistry Final
14. What shape is a water molecule?
Bent
12. a gas occupies a volume of 180 ml at 25.0 °C and 95.9 kPa. What is the volume of the gas at STP?
1.56 L
20. Calculate the boiling point of a solution that contains 191.07 g K₃PO₄ dissolved in 2750 g of water.
101°C
14. What is the bond angle of a water molecule?
105°
6. If 6.5 L oxygen react at STP, how many liters of nitrogen dioxide are produced? 2NO + O₂ → 2NO₂
13.0 L
number of molecules
a neutral group of atoms joined together by covalent bonds; in stoichiometry, equal to 6.02 x 10²³ molecules/mol.
19. What is the freezing point of a solution that contains 2.0 mol of calcium chloride, CaCl₂, in 800.0 g water?
-14° C
18. Define deliquescent, hygroscopic, and efflorescent
-Deliquescent: Describes a substance that removes sufficient water from the air to form a solution; the solution formed has a lower vapor pressure than that of the water in the air. -Hygroscopic: A term describing salts and other compounds that remove moisture from the air -Efflorescent: to lose water of hydration; the process occurs when the hydrate has a vapor pressure higher than that of water vapor in the air
1. How many moles are in 45 grams NaI?
0.30 mol
2. How many carbon atoms are in one mole glucose? How many in 8 moles?
1 mol = 3.61 x 10²⁴ atoms C 8 mol = 2.89 x 10²⁵ atoms C
14. List five properties of water that are attributed to this type of bond (that holds one water molecule to the next)?
1) High Surface Tension: The inward force, or pull, that tends to minimize the surface area of a liquid is called surface tension. Most liquids have a surface tension, but water's surface tension is higher than most. Basically, the hydrogen bonds are strong enough to cause the molecules to form a drop instead of spread out. 2) Low Vapor Pressure: Hydrogen bonding between water molecules also explains water's unusually low vapor pressure. Because hydrogen bonds hold water molecules to one another, the tendency of these molecules to escape is low, and evaporation is slow. 3) Ice is less dense than Liquid Water: As water begins to cool, it behaves initially like a typical liquid. It contracts slightly and its density gradually increases. When the temperature of the water falls below 4˚C, the density of water starts to decrease. Hydrogen bonds hold the water molecules in place in the solid phase. The structure of ice is a regular open framework of water molecules arranged like a honeycomb. The molecules are as far apart as they can get. When ice melts, the framework collapses, and the water molecules pack closer together, making liquid water more dense than ice. 4) High Boiling Point: You need a higher temp to break the bonds so particles can leave. 5) High freezing point: Water has strong hydrogen bonds, so it is harder to break the bonds, and intermolecular forces bond bonds easily due to the polarity.
14. Use Graham's law to calculate how much faster fluorine gas, F₂ , will effuse than chlorine gas, Cl₂, will. The molar mass of F₂ = 38.0; the molar mass of Cl₂ = 70.9.
1.37 x faster
21. Calculate the molarity of a solution that contains 50.0 grams of Mg(NO₃)₂ in 225 mL of solution.
1.50 M
4. How many liters are occupied by one mole of oxygen? nitrogen? carbon dioxide?
22.4 L
volume (as related to the mole)
22.4 L/mol
3. What volume is occupied by 6.5 x 10³ grams carbon dioxide at STP?
3.3 x 10³ L
7. The volume of a gas at 155.0 kPa changes from 22.0 L to 10.0 L. What is the new pressure if the temperature remains constant?
341 kPa
15. The solubility of a gas in water is 1.6 g/L at 1.0 atm. What is the solubility of the same gas at 2.5 atm? Assume the temperature is constant.
4.0 g/L
10. How many grams of helium does a 25.0 L balloon contain at 102.0 kPa and 24 °C?
4.12 gHe
11. A mixture of gases at a total pressure of 145.0 kPa contains nitrogen, carbon dioxide, and oxygen. The partial pressure of nitrogen is 28.5 kPa, and the partial pressure of carbon dioxide is 76.0 kPa. What is the partial pressure of oxygen?
40.5 kPa
13. The gaseous product of a reaction is collected in a 25.0 L container at 27.0 °C. The pressure in the container is 216 kPa, and the gas has a mass of 96 g. What is the molar mass of the gas?
44 g/mol
8. A gas at a pressure of 501 kPa and a temperature of 25 °C occupies a volume of 5.2 L. When the gas is heated to 100.0°C the volume increases to 7.00 L. What is the new pressure?
466 kPa
9. Calculate the volume that 2.25 mole of oxygen will occupy at STP.
50.4 L
16. What mass sucrose, C₁₂H₂₂O₁₁, is needed to make 300 ml of a 0.50 M solution?
51 g
5. If 50.0 grams CaCO₃ react to produce 20.0 g CO₂, what is the percent yield of the reaction? CaCO₃ → CaO + CO₂
90.9%
empirical formula
A formula with the lowest whole-number ratio of elements in a compound; the empirical formula of hydrogen peroxide (H₂O₂) is HO
excess reagent
A reagent present in a quantity that is more than sufficient to react with a limiting reagent; any reactant that remains after the limiting reagent is used up in a chemical reaction.
theoretical yield
The amount of product that could form during a reaction calculated from a balanced chemical equation; it represents the maximum amount of product that could be formed from a given amount of reactant.
actual yield
The amount of product that forms when a reaction is carried out in the laboratory
4. Ammonia and copper (II) oxide react according to the following: 2NH₄ + 3CuO → N₂ + 3Cu + 3H₂O If 57.0 g ammonia are combined with 290.0 g CuO: A. What is the limiting reagent? B. How much excess reactant remains, in moles? C. What mass of nitrogen is produced?
A. CuO B. 0.74 mol C. 34.1
17. How many moles of solute particles are produced by adding one mole of each of the following to water? AlCl₃, C₁₂H₂₂O₁₁, NaNO₃, KI, C₆H₆
AlCl₃ = 4 C₁₂H₂₂O₁₁ = 1 NaNO₃ = 2 KI = 2 C₆H₆ = 1
limiting reagent
Any reactant that is used up first in a chemical reaction; it determines the amount of product that can be formed in the reaction
11. Review Dalton's law of partial pressure.
At constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component gases. Total P = P₁ + P₂ + P₃ + ...
12. What criteria would you use to select a gas to keep a balloon inflated for a long period of time?
Choose one with a high molar mass, such as sulfur hexafluoride, since it will effuse/diffuse slowly.
19. Describe the temperature change in a substance as it undergoes phase change.
During a phase change, the temperature doesnt change.
13. List two gases, circle that gas that would effuse the fastest and explain why.
During effusion, a gas escapes through a tiny hole in its container. Gases of lower molar mass diffuse and effuse faster than gases of higher molar mass. Helium molar mass = 4.0 g Nitrogen molar mass = 28.0 g He would effuse faster because it has a lower molar mass. Graham's Law: RateA/RateB = √mmB/mmA RateHe/RateN₂ = √28.0g/4.0g = √7 = 2.7
1. List the representative particles for elements, molecules (ionic and covalent).
Element: Atom Diatomic: Molecule Ionic: Formula Unit Covalent: Molecule
17. How does increasing the temperature of water change the amount of solid solute that will dissolve?
For a solid or liquid solute, the higher the temperature, the more that can be dissolved. For a gas solute, the lower the temperature, the more that can be dissolved (soda).
18. What is the molal freezing point constant for water? The molal boiling point constant for water?
Freezing Point Constant = 1.86° C/m Boiling Point Constant = 0.512° C/m
14. Which atom has the higher electronegativity in water?
H2O, is a simple molecule consisting of three atoms. The oxygen atom forms a covalent bond with each of the hydrogen atoms. Oxygen has a greater electronegativity than hydrogen, so the oxygen atom attracts the electron pair of the covalent O—H bond to a greater extent than the hydrogen atom. Thus, the O—H bond is highly polar. As a result, the oxygen atom acquires a partial negative charge (δ−). The less electronegative hydrogen atoms acquire partial positive charges (δ+).
15. State Henry's law. Explain why increasing the pressure above a liquid also increases the amount of gas that can dissolve into the liquid. List two substances whose solubility is increased by increasing the pressure above water.
Henry's law states that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid. As pressure above a gas goes up, the amount of gas that can be dissolved goes up. S/P=S/P CO2 & O2
14. What type of bond holds one water molecule to the next?
Hydrogen
3. List the seven diatomic elements and their molar masses.
Hydrogen (H₂): 2(1.0)= 2.0 Nitrogen (N₂): 2(14.0)= 28.0 Oxygen (O₂): 2(16.0)= 32.0 Fluorine (F₂): 2(19.0)= 38.0 Chlorine (Cl₂): 2(35.5)= 71.0 Bromine (Br₂): 2(79.9)= 159.8 Iodine (I₂): 2(126.9)= 253.8
10. How does increasing the number of molecules in a container affect pressure?
Increasing the number of molecules in a container increases the pressure, because more particles means more collisions.
7. ways to interpret balanced equations.
Interpret: 2CO(g) + O₂(g) → 2CO₂(g) Moles: 2molCO + 1molO₂ → 2molCO₂ Mass: 56gCO + 32gO₂ → 88gCO₂ Volume: 44.8LCO + 22.4LO₂ → 44.8LCO₂ Molecules: 2mclCO + 1mclO₂ → 2mclCO₂ Atoms: 2atomsC + 2atomsO +2atomsO → 2atomsC + 4atomsO
9. How does raising temperature affect pressure and volume? How does decreasing volume affect temperature and pressure? How does increasing pressure affect temperature and volume?
LOOK TO SEE-SAW PAPER (PTV) As P goes up, T goes up and V goes down. As P goes down, T goes down and V goes up. As V goes up, T goes up and P goes down. As V goes down, T goes down and P goes up. As T goes up, P and V go up. As T goes down, P and V go down.
7. Review mole ratios in balanced equations.
Mole Ratio: a conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles
2. What is the mass in grams of 1.8 x 10²⁵ ∆molecules nitrogen? Atoms of nitrogen?
Molecules = 840g Atoms = 3.6 x 10^25 atoms
16. List two substances that are soluble in water. List two substances that are insoluble in water.
Soluble: NaCl/C6H12O6 Insoluble: Oil/Sand
6. What is conserved in EVERY chemical reaction? What are the quantities that are not always (but sometimes are) conserved?
Sometimes: Moles, Volume, Molecules Always: Mass, Atoms
mole
The amount of a substance that contains 6.02 x 10²³ representative particles of that substance
STP
Standard Temperature and Pressure; the conditions under which the volume of a gas is usually measured; standard temperature is 0°C, and standard pressure is 101.3 kPa, or 1 atmosphere (atm)
14. Is this type of bond (that holds one water molecule to the next) considered strong or weak? Explain why.
Strong; high surface tension, low vapor pressure, high boiling point
molality
The concentration of solute in a solution expressed as the number of moles of solute dissolved in 1 kilogram (1000 g) of solvent
molarity
The concentration of solute in a solution expressed as the number of moles of solute dissolved in 1 liter of solvent
boiling point elevation
The difference in temperature between the boiling point of a solution and the boiling point of the pure solvent.
freezing point depression
The difference in temperature between the freezing point of a solution and the freezing point of the pure solvent.
mass
The measure of the amount of matter that an object contains ; the SI base unit of mass is the kilogram
Avogadro's number
The number of representative particles contained in one mole of a substance; equal to 6.02 x 10²³ particles
percent composition
The percent by mass of each element in a compound
percent yield
The ratio of the actual yield to the theoretical yield for a chemical reaction expressed as a percentage; a measure of the efficiency of a reaction
mole fraction
The ratio of the moles of solute in solution to the total number of moles of both solvent and solute.
representative particle
The smallest unit into which a substance can be broken down without a change in composition, usually atoms, molecules, or ions
14. What bond holds the oxygen to the hydrogen within a water molecule?
covalent bonds
5. How is percent composition calculated? What is the percent nitrogen in ammonia nitrate? Percent composition of carbon in carbon dioxide?
• The percent by mass of each element in a compound • The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100%. • The relative amounts of the elements in a compound are expressed as the percent composition or the percent by mass of each element in the compound. • Ammonium Nitrate = 35% N • Carbon Dioxide = 27% C
8. How is limiting reagent determined? How is amount of excess reagent left over calculated?
∼ LR: Any reactant that is used up first in a chemical reaction; it determines the amount of product that can be formed in the reaction. ∼ ER: A reagent present in a quantity that is more than sufficient to react with a limiting reagent; any reactant tat remains after the limiting reagent is used up in a chemical reaction. ∼ To find LR, convert the given amounts of reactants into the same product (Mole Map). The reactant that produces the smaller amount of product is the limiting reagent. The reactant that produces the larger amount of product is the excess reagent. ∼ To find ER left over, convert the given for limiting reagent to excess reagent. Finally, subtract the answer from the given for excess reagent.