Chemistry: Exothermic and Endothermic Reactions
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Questions and Answers

Which of the following statements is true regarding exothermic reactions?

  • Energy is a reactant.
  • Reactants have less energy than the products.
  • Energy is a product. (correct)
  • Enthalpy change is always positive.

    • In an endothermic reaction, products possess less energy than the reactants.

    False

    What does the symbol ΔH represent in a chemical reaction?

    Enthalpy change

    An exothermic reaction has a __________ energy change.

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

    Match the energy change type with its description:

    <p>Exothermic = Energy is released, reactants have more energy Endothermic = Energy is absorbed, products have more energy Enthalpy = Total heat content of a chemical system ΔH = Change in enthalpy during a reaction</p> Signup and view all the answers

    What type of reaction is cellular respiration?

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

    Photosynthesis produces carbon dioxide and water.

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

    What is the balanced equation for cellular respiration?

    <p>C6H12O6 + 6O2 -&gt; 6CO2 + 6H2O + 35099.6kJ</p> Signup and view all the answers

    Photosynthesis is an __________ reaction that requires energy.

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

    Match the following terms with their definitions:

    <p>Cellular Respiration = Energy-releasing process Photosynthesis = Energy-absorbing process Exothermic Reaction = Releases heat energy Endothermic Reaction = Absorbs heat energy</p> Signup and view all the answers

    Which statement is correct regarding enthalpy change (ΔH)?

    <p>A negative ΔH indicates an exothermic reaction.</p> Signup and view all the answers

    Chemical reactions are not influenced by the coefficients in a chemical equation.

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

    What is the ΔH for the reaction 2 N2(g) + 6 H2(g) → 4 NH3(g)?

    <p>-100 kJ</p> Signup and view all the answers

    Reactions with a positive ΔH are _____, meaning they gain energy.

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

    Match the following chemical equations with their respective ΔH values:

    <p>N2(g) + 3 H2(g) → 2 NH3(g) = -90 kJ 2 N2(g) + 6 H2(g) → 4 NH3(g) = -100 kJ 3 N2(g) + 9 H2(g) → 6 NH3(g) = -270 kJ</p> Signup and view all the answers

    What is the overall enthalpy change ( abla H) for the given reaction?

    <p>+35099.6 kJ</p> Signup and view all the answers

    Molar enthalpy can be expressed as the total enthalpy change divided by the number of moles.

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

    What is the equation used to calculate enthalpy change?

    <p>ΔH = nH_m</p> Signup and view all the answers

    In the equation $ abla H = nH_m$, the variable 'n' represents the _______.

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

    Match the following terms with their correct definitions:

    <p>Enthalpy within a chemical reaction = The heat absorbed or released during a reaction Overall enthalpy change = The total change in enthalpy for a reaction Molar enthalpy = Enthalpy change per mole of substance Potential energy diagram = Graphical representation of energy changes during a reaction</p> Signup and view all the answers

    What is the standard molar enthalpy of combustion of gasoline?

    <p>-5074.1 kJ/mol</p> Signup and view all the answers

    The enthalpy change for burning 737 g of gasoline is positive.

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

    How many moles of gasoline are in 737 g?

    <p>6.4502</p> Signup and view all the answers

    The enthalpy change for burning one litre of gasoline is approximately __________ kJ.

    <p>-3.27 x 10^4</p> Signup and view all the answers

    Match the following quantities with their corresponding calculations:

    <p>Hm = -5074.1 kJ/mol moles of gasoline = 6.4502 mol mass of gasoline = 737 g total enthalpy change = -3.27 x 10^4 kJ</p> Signup and view all the answers

    What is the molar enthalpy of reaction for NiO(l) in the reaction 2 Al(l) + 3 NiO(l) → Al2O3(s) + 3 Ni(l) + 954 kJ?

    <p>-318 kJ/mol</p> Signup and view all the answers

    Exothermic reactions absorb energy from their surroundings.

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

    What does the reaction 2 Al(l) + 3 NiO(l) produce?

    <p>Al2O3(s) and 3 Ni(l)</p> Signup and view all the answers

    In the reaction 2 Al(l) + 3 NiO(l) → Al2O3(s) + 3 Ni(l) + 954 kJ, energy is __________.

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

    Match the following substances with their role in the reaction:

    <p>Al(l) = Reactant that is oxidized NiO(l) = Reactant that is reduced Al2O3(s) = Product formed Ni(l) = Product formed</p> Signup and view all the answers

    What is the molar enthalpy of reaction for carbon dioxide in the fermentation reaction?

    <p>-29.2 kJ/mol</p> Signup and view all the answers

    The original source of energy stored in glucose is the Sun.

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

    How many kilograms of methanol are required to produce an enthalpy change of -9.00 x 104 kJ?

    <p>4.52 kg</p> Signup and view all the answers

    In the reaction of methanol, the heat released is represented by ΔH = __________ kJ.

    <p>-1275.8</p> Signup and view all the answers

    Match the following components to their respective roles:

    <p>C6H12O6 = Substrate in fermentation 2H2O = Product of combustion in methanol reaction O2 = Reactant in methanol combustion 3CO2 = Byproduct of fermentation</p> Signup and view all the answers

    What is the standard molar enthalpy of combustion, $ riangle H^ heta$, for ethyne?

    <p>-1 301.1 kJ/mol</p> Signup and view all the answers

    The combustion of ethyne produces four moles of carbon dioxide and two moles of water.

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

    What is the coefficient for $O_2(g)$ in the complete combustion of ethyne equation?

    <p>5</p> Signup and view all the answers

    In the given combustion reaction, ethyne ($C_2H_2(g)$) reacts with __________ gas.

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

    Match the compounds with their respective coefficients in the combustion of ethyne:

    <p>$C_2H_2(g)$ = 5 $O_2(g)$ = 5 $CO_2(g)$ = 4 $H_2O(l)$ = 2</p> Signup and view all the answers

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