Chemistry Gases and Significant Figures Quiz
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Questions and Answers

Which of the following is NOT a rule for counting significant figures?

  • Zeros after the decimal and after the number are significant.
  • All non-zero digits are significant.
  • Zeros between significant figures are significant.
  • Zeros standing alone before a decimal point are significant. (correct)

    • In multiplication, the result must have the same number of decimal places as the factor with the smallest number of decimal places.

    False

    What is the primary role of nitrogen in plant growth?

    Nitrogen is converted into nitrogen-containing compounds that plants can absorb.

    The main oxidizer in combustion reactions is __________.

    <p>oxygen</p> Signup and view all the answers

    Match the gas to its corresponding significance:

    <p>Nitrogen = Vital for plant growth Oxygen = Essential for respiration Carbon Dioxide = Major greenhouse gas Methane = Main component of biogas</p> Signup and view all the answers

    Which gas is most commonly produced by photosynthesis?

    <p>Oxygen</p> Signup and view all the answers

    Gases have a defined shape and volume.

    <p>False</p> Signup and view all the answers

    What percentage of the Earth's atmosphere is composed of nitrogen?

    <p>78%</p> Signup and view all the answers

    What happens to radon gas in confined spaces?

    <p>It can cause lung cancer.</p> Signup and view all the answers

    Oxygen is only used for supporting flames.

    <p>False</p> Signup and view all the answers

    What component must be present for combustion to occur?

    <p>Oxidizer, fuel, and source of ignition</p> Signup and view all the answers

    The gas that is used in welding torches is called _______.

    <p>acetylene</p> Signup and view all the answers

    Match the gases with their applications:

    <p>Nitrogen = Inflating tires in airplanes Carbon Dioxide = Extinguishes fires Fluorine = Used in toothpaste Ozone = Protects from UV rays</p> Signup and view all the answers

    Which gas is considered a noble gas?

    <p>Radon</p> Signup and view all the answers

    All noble gases have a high level of chemical reactivity.

    <p>False</p> Signup and view all the answers

    What is Graham’s Law used to explain?

    <p>The rates of diffusion and effusion of gases.</p> Signup and view all the answers

    Fluorine is very toxic and used in compounds in the form of __________ ions.

    <p>fluoride</p> Signup and view all the answers

    Match the gases with their characteristics:

    <p>Nitrogen = Preserves foods Oxygen = Supports flames Radon = Produced from uranium decay Carbon Dioxide = Shoots paintballs</p> Signup and view all the answers

    What is the result of the combustion process?

    <p>Energy release</p> Signup and view all the answers

    The average kinetic energy of gas particles is independent of the gas type.

    <p>True</p> Signup and view all the answers

    Which gas is commonly used in the pressurization of aircraft cabins?

    <p>Oxygen</p> Signup and view all the answers

    The pressure of gases is defined as the force they exert over a certain area, expressed as P = F/A, where P is pressure measured in _______.

    <p>Pascals</p> Signup and view all the answers

    Match the components of the fire triangle with their definitions:

    <p>Oxidizer = Supports combustion Fuel = Substance that burns Source of ignition = Triggers combustion Heat = Energy causing combustion</p> Signup and view all the answers

    What happens to gas pressure if temperature increases while keeping the amount of gas constant?

    <p>Pressure increases</p> Signup and view all the answers

    Atmospheric pressure is the same at all altitudes.

    <p>False</p> Signup and view all the answers

    Define Boyle's Law.

    <p>At a constant temperature, the volume of a given quantity of gas is inversely proportional to the pressure exerted on it.</p> Signup and view all the answers

    At standard conditions, 1 mole of a gas occupies a volume of ____ L.

    <p>22.4</p> Signup and view all the answers

    What unit is used to measure atmospheric pressure at sea level?

    <p>All of the above</p> Signup and view all the answers

    Since gas particles are negligible, the size of the gas particles does influence the volume they occupy.

    <p>False</p> Signup and view all the answers

    What does Gay-Lussac's Law describe?

    <p>It describes how, at constant volume, the pressure of a given quantity of gas is directly proportional to its absolute temperature.</p> Signup and view all the answers

    The formula for Charles’ Law is ____.

    <p>V1/T1 = V2/T2</p> Signup and view all the answers

    According to Avogadro's Law, under the same temperature and pressure, what happens to the volume ratio of gases?

    <p>It equals the mole ratio</p> Signup and view all the answers

    The ideal gas law applies to solids and liquids.

    <p>False</p> Signup and view all the answers

    What happens to the volume of a gas when pressure is increased at constant temperature?

    <p>The volume decreases.</p> Signup and view all the answers

    Match the gas laws with their definitions:

    <p>Boyle's Law = Volume decreases with increased pressure at constant temperature Charles' Law = Volume increases with increased temperature at constant pressure Gay-Lussac's Law = Pressure increases with temperature at constant volume Avogadro's Law = Volume is directly proportional to the number of moles at constant temperature and pressure</p> Signup and view all the answers

    The absolute zero temperature is ____ degrees Celsius.

    <p>-273</p> Signup and view all the answers

    What is the pressure exerted by the air at sea level in kPa?

    <p>101.3</p> Signup and view all the answers

    What does the ideal gas law equation PV = nRT represent?

    <p>Relationship between pressure, volume, temperature, and moles of gas</p> Signup and view all the answers

    The Van der Waals equation considers the volume occupied by gas molecules.

    <p>True</p> Signup and view all the answers

    What happens to the pressure of a real gas compared to an ideal gas?

    <p>It is slightly lower because real gas particles lose energy during collisions.</p> Signup and view all the answers

    According to Dalton’s Law, the total pressure in a mixture is equal to the sum of __________ pressures.

    <p>partial</p> Signup and view all the answers

    Match the following gas laws with their descriptions:

    <p>Ideal Gas Law = PV = nRT Dalton’s Law = Total pressure = sum of partial pressures Van der Waals Equation = Adjusts ideal gas law for real gas behavior General Gas Law = P1V1 / n1T1 = P2V2 / n2T2</p> Signup and view all the answers

    Which variable does 'R' represent in the ideal gas law?

    <p>Gas constant</p> Signup and view all the answers

    Heat energy moves from a cooler system to a warmer system until equilibrium is reached.

    <p>False</p> Signup and view all the answers

    What does the term 'calorimetry' refer to?

    <p>The experimental method used to determine the quantity of heat changes.</p> Signup and view all the answers

    The gas law used to find density is d = __________.

    <p>MP / RT</p> Signup and view all the answers

    Match the type of system to its description:

    <p>Open system = Energy and matter can be exchanged with surroundings Closed system = Energy can be exchanged, but not matter Isolated system = Neither energy nor matter can be added or removed</p> Signup and view all the answers

    What is the primary function of a calorimeter?

    <p>Determine heat changes in reactions</p> Signup and view all the answers

    Real gases behave like ideal gases at low temperatures and high pressures.

    <p>False</p> Signup and view all the answers

    What happens to particles of a real gas as temperature decreases?

    <p>They slow down and move closer together.</p> Signup and view all the answers

    __________ is the transfer of thermal energy between systems at different temperatures.

    <p>Heat</p> Signup and view all the answers

    In the equation P1V1 / n1T1 = P2V2 / n2T2, what does the term 'R' represent?

    <p>Gas constant</p> Signup and view all the answers

    What does the symbol Q represent in the energy transfer equation?

    <p>Quantity of heat</p> Signup and view all the answers

    In an exothermic reaction, the surroundings absorb heat from the system.

    <p>False</p> Signup and view all the answers

    Define enthalpy change (△H).

    <p>The energy exchanged between a system and its environment during a physical change or chemical reaction at constant pressure.</p> Signup and view all the answers

    The formula for calculating energy transfer is Q = mc△t, where m stands for ______.

    <p>mass</p> Signup and view all the answers

    Match the following types of reactions with their descriptions:

    <p>Endothermic = Absorbs heat from surroundings Exothermic = Releases heat into surroundings Chemical Reaction = Involves breaking and forming bonds Phase Change = Change of substance state</p> Signup and view all the answers

    Which of the following indicates an endothermic reaction?

    <p>△H is positive</p> Signup and view all the answers

    In the equation △Hr = Sum of △Hreactants - Sum of △Hproducts, a negative result indicates an endothermic reaction.

    <p>False</p> Signup and view all the answers

    What is the relationship between bond energies and enthalpy changes in chemical reactions?

    <p>The energy required to break bonds in reactants compared to the energy released when forming bonds in products determines the enthalpy change.</p> Signup and view all the answers

    When one mole of solute dissolves in water, the process is called molar heat of ______.

    <p>dissolution</p> Signup and view all the answers

    Match the following energy changes with their characteristics:

    <p>Endothermic = Energy absorbed, surroundings get cooler Exothermic = Energy released, surroundings get warmer Phase change = Transition between solid, liquid, or gas Molar heat of reaction = Energy change per mole of substance</p> Signup and view all the answers

    Which statement about bond energies is accurate?

    <p>Bond energies are necessary to calculate enthalpy changes.</p> Signup and view all the answers

    For a chemical reaction to be endothermic, the energy required to break reactant bonds must be greater than the energy released from product bonds.

    <p>True</p> Signup and view all the answers

    How is heat transfer between two systems characterized?

    <p>One system releases heat (negative Q) while the other absorbs it (positive Q).</p> Signup and view all the answers

    The energy change for a reaction can also be expressed as △Hr = ______.

    <p>Sum of △Hreactants - Sum of △Hproducts</p> Signup and view all the answers

    What is the formula for calculating the enthalpy change during a molar reaction?

    <p>nH = -mcΔt</p> Signup and view all the answers

    In an exothermic reaction, the products have a higher energy level than the reactants.

    <p>False</p> Signup and view all the answers

    What does MC stand for in the formula for neutralization?

    <p>molar concentration</p> Signup and view all the answers

    In a neutralization reaction, H is calculated using the formula H = -mcΔt / (MC x V). This indicates that H represents the ______ change associated with the reaction.

    <p>enthalpy</p> Signup and view all the answers

    Match the reaction types with their corresponding characteristics:

    <p>Combustion = Exothermic reaction that releases heat Neutralization = Exothermic reaction between an acid and a base Dissolution = Process where solute interacts with solvent Enthalpy change = Difference in energy between products and reactants</p> Signup and view all the answers

    What indicates a reaction is endothermic when analyzing an enthalpy diagram?

    <p>ΔH is positive</p> Signup and view all the answers

    The formula Q = mcΔt can be used to calculate heat transfer in a system undergoing a phase change.

    <p>False</p> Signup and view all the answers

    What is the significance of the equation Q = -mcΔt in heat transfer?

    <p>It indicates heat transfer between two objects with no heat loss.</p> Signup and view all the answers

    What is the expected sign of ΔHd when H1 + H2 < H3?

    <p>Negative (Exothermic)</p> Signup and view all the answers

    The molar heat of neutralization is always endothermic.

    <p>False</p> Signup and view all the answers

    What does Q represent in the energy equation Q = mcΔt?

    <p>The amount of heat energy required to change the temperature.</p> Signup and view all the answers

    The enthalpy change of a substance during combustion is denoted as ______.

    <p>Hc</p> Signup and view all the answers

    Match the following concepts with their descriptions:

    <p>ΔHd = Heat of dissolution Hn = Heat of neutralization Hc = Heat of combustion ΔT = Change in temperature</p> Signup and view all the answers

    In the calorimetry equation nHc = -mcΔt, what does mc represent?

    <p>Mass multiplied by specific heat capacity</p> Signup and view all the answers

    The enthalpy change for a complex reaction can be determined by summing the enthalpy changes of its simple reactions.

    <p>True</p> Signup and view all the answers

    When a substance dissolves in water and absorbs heat, what type of reaction is it?

    <p>Endothermic</p> Signup and view all the answers

    When measuring molar heat of neutralization, we assume that dilute acid and base solutions have the same ______ and ______ as water.

    <p>density, specific heat capacity</p> Signup and view all the answers

    Match the following heat formulas with their meanings:

    <p>Q = mcΔt = Heat transfer with temperature change Q = nH = Heat during phase change Q = -Q = Energy conservation nHD = -mcΔt = Heat absorbed by water</p> Signup and view all the answers

    What type of reaction involves the formation of oppositely charged ions from dissolving an ionic compound?

    <p>Exothermic</p> Signup and view all the answers

    Heat released in combustion must equal the heat absorbed by the water in calorimetry.

    <p>True</p> Signup and view all the answers

    What will happen to the temperature of water if the dissolution is exothermic?

    <p>The temperature will increase.</p> Signup and view all the answers

    Molar heat of dissolution, ΔHd, is calculated using the formula ΔHd = ΔH1 + ΔH2 + ΔH3, where H3 represents ______ energy.

    <p>exothermic</p> Signup and view all the answers

    Study Notes

    Significant Figures (Sig Figs)

    • Sig figs indicate the certainty of a measurement.
    • All non-zero digits are significant.
    • Zeros between significant digits are significant.
    • Zeros after the decimal point and after a number are significant.
    • Zeros alone before a decimal point are not significant.
    • A zero after a number and before a decimal point is significant.
    • Zeros before a non-zero digit and after a decimal point are not significant.
    • Ignore decimals, multiples, and submultiples of powers of 10 when counting sig figs.

    Sig Fig Rules During Calculations

    • Addition/Subtraction: The answer's decimal places are determined by the measurement with the fewest decimal places.
    • Multiplication/Division: The answer's significant figures are determined by the measurement with the fewest significant figures.
    • Complex calculations: Perform addition/subtraction and multiplication/division separately, then combine results according to the rules above

    Unit 1: Gases - Chemical Properties

    • Gases are fluid, have indefinite volume and shape, and tend to diffuse.
    • Earth's atmosphere is a mixture of mainly nitrogen (78%), oxygen (21%), and carbon dioxide (0.03%).
    • Nitrogen is vital for plant growth.
    • Oxygen is vital for cellular respiration.
    • Carbon dioxide is a greenhouse gas.
    • Methane (CH4) is a greenhouse gas from anaerobic decomposition.
    • Radon (Rn) is a radioactive noble gas, harmful in confined spaces.
    • Gases have various technological applications: food preservation, fertilizer production, vehicle inflation, medical support, and various industrial processes.

    Chemical Reactivity of Gases

    • Reactivity depends on electron configuration, noble gases are unreactive, halogens are highly reactive.
    • Reactivity also depends on electronegativity (strength of attraction).
    • Strong bonds lead to lower reactivity (e.g., N2).
    • Combustion requires an oxidizer, fuel, and ignition source.
    • Hydrocarbons (CxHy) are combustible.
    • Oxygen is the most common oxidizer.

    Unit 1: Gases - Physical Properties

    Kinetic Theory of Gases

    • Gas particles are tiny, in constant motion, collide elastically, and have no intermolecular forces.
    • Average kinetic energy is directly proportional to absolute temperature.
    • Gases expand to fill containers.

    Diffusion and Effusion (Graham's Law)

    • Diffusion is the mixing of gases.
    • Effusion is the escape of gas through a small hole.
    • Graham's Law: Rate of diffusion/effusion is inversely proportional to the square root of molar mass. (V1/V2 = √(M2/M1) )

    Pressure

    • Pressure is force per unit area (P = F/A).
    • Atmospheric pressure decreases with altitude.
    • Pressure is affected by particle collisions and temperature.

    Simple Gas Laws

    • Boyle's Law: P1V1 = P2V2 (constant T and n)
    • Charles' Law: V1/T1 = V2/T2 (constant P and n) (Temperature MUST be in Kelvin!)
    • Gay-Lussac's Law: P1/T1 = P2/T2 (constant V and n) (Temperature MUST be in Kelvin!)
    • Avogadro's Law: V1/n1 = V2/n2(constant T and P)

    Molar Volume

    • Molar volume (STP/SATP) is the volume occupied by 1 mole of any gas under specific conditions.

    Ideal Gas Law

    • PV = nRT (P=pressure, V=volume, n=moles, R=ideal gas constant, T=temperature in Kelvin)

    Other Applications of the Ideal Gas Law

    • Finding molar mass using the Ideal Gas Law.
    • Finding density using the Ideal Gas Law.

    General Gas Law

    • Combines Boyle's, Charles', and Avogadro's Laws. (P1V1/n1T1 = P2V2/n2T2)

    Stoichiometry of Gases

    • Relates gaseous moles to volume using the ideal gas law or molar volume at STP/SATP.

    Dalton's Law of Partial Pressures

    • Ptotal = P1 + P2 +... (Sum of partial pressures of components)
    • Partial pressure is determined by the component's mole fraction multiplied by the total pressure (P1=Ptotal x n1/ntotal) Mole fraction: fraction of the number of moles of one component to the total number of moles of the mixture

    Van der Waals Equation

    • Corrects for deviations from ideal gas behavior at high pressures and low temperatures. [ P + (an2/V2) ] ( V - nb ) = nRT (a=attraction between particles, b=volume occupied by particles) P = pressure, V = Volume, n = number of moles, R =ideal gas constant, T = temperature in Kelvin

    Unit 2: Energy - Energy Transfer

    Heat vs. Temperature

    • Heat is energy transfer due to temperature difference. Moves from higher to lower temperatures until equilibrium.
    • Temperature is a measure of particle motion's intensity.

    Law of Conservation of Energy

    Energy is neither created nor destroyed, only transferred or transformed. Open, closed, and isolated systems.

    Calorimetry

    • Calorimetry measures heat involved in changes. Calorimeter is a rigid container mostly in a water bath to isolate it from the surroundings.

    Calculating Thermal Energy

    • Q = mcΔt ( Q=heat, m=mass, c=specific heat, Δt=change in temperature)

    Calculating Heat Transfer

    • Involves heat exchange between two systems until equilibrium is reached.

    Unit 2: Energy - Enthalpy Change

    • Enthalpy (H) is total energy of a system at constant pressure.
    • Enthalpy change (ΔH) is heat exchanged during a constant pressure process.

    Standard Molar Enthalpy Change (Phase Change)

    • ΔH = Hproducts– Hreactants
    • ΔH is positive for endothermic processes and negative for exothermic processes.

    Endothermic vs. Exothermic Reactions

    • Endothermic processes absorb heat from surroundings, resulting in a positive ΔH.
    • Exothermic processes release heat to surroundings, resulting in a negative ΔH.

    Energy Balance/Bond Energies

    • Reactant bonds broken, product bonds formed.
    • Enthalpy change: sum of bond breaking energies - sum of bond forming energies.

    Stoichiometry of the Enthalpy Change

    • Enthalpy change is proportional to the number of moles.

    Molar Heat of Reactions

    • Measures energy during specific physical changes or chemical reactions. Types include dissolution(ionization), neutralization(acid/base), combustion.

    Molar Heat of Dissolution

    • Heat associated with one mole of solute dissolving in a solvent/water.
    • Endothermic (positive ΔHd) if solvent-solute attraction is weaker than solvent-solvent or solute-solute interactions.
    • Exothermic (negative ΔHd) if the attraction is stronger. ΔHd = ΔH1 + ΔH2 + ΔH3 (Solvent-Solvent, Solute-Solute, Solute-Solvent) The heat released or absorbed in the dissolution of the solute equals the heat lost or gained by the water △Hd= -Q

    Molar Heat of Neutralization

    • Heat released/absorbed when one mole of acid/base neutralizes. (Always exothermic)

    • Hn = -mcΔt / (concentration x volume)

    Molar Heat of Combustion

    • Heat released when one mole of substance burns. Hc = -mcΔt / (moles of substance)

    Hess's Law

    • Calculate the enthalpy of a reaction using known enthalpy changes of multiple steps.
    • Reverse, multiply steps to align with desired reaction. Add ΔH values algebraically.

    Energy Formulas Summary

    • Provide specific formulas for each type of energy calculation (temperature change, phase change, reaction).

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    Description

    Test your knowledge on significant figures and the role of various gases in chemistry. This quiz covers key concepts such as combustion, photosynthesis, and noble gases. Make sure to review the rules and applications of these gases before attempting!

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