Chemistry: Exothermic and Endothermic Reactions

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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 (B)

What does the symbol ΔH represent in a chemical reaction?

Enthalpy change

An exothermic reaction has a __________ energy change.

negative Signup and view all the answers

Match the energy change type with its description:

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 Signup and view all the answers

What type of reaction is cellular respiration?

Exothermic (D) Signup and view all the answers

Photosynthesis produces carbon dioxide and water.

False (B) Signup and view all the answers

What is the balanced equation for cellular respiration?

C6H12O6 + 6O2 -> 6CO2 + 6H2O + 35099.6kJ Signup and view all the answers

Photosynthesis is an __________ reaction that requires energy.

endothermic Signup and view all the answers

Match the following terms with their definitions:

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

Which statement is correct regarding enthalpy change (ΔH)?

A negative ΔH indicates an exothermic reaction. (C) Signup and view all the answers

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

False (B) Signup and view all the answers

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

-100 kJ Signup and view all the answers

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

endothermic Signup and view all the answers

Match the following chemical equations with their respective ΔH values:

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 Signup and view all the answers

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

+35099.6 kJ (D) Signup and view all the answers

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

True (A) Signup and view all the answers

What is the equation used to calculate enthalpy change?

ΔH = nH_m Signup and view all the answers

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

moles Signup and view all the answers

Match the following terms with their correct definitions:

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 Signup and view all the answers

What is the standard molar enthalpy of combustion of gasoline?

-5074.1 kJ/mol (A) Signup and view all the answers

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

False (B) Signup and view all the answers

How many moles of gasoline are in 737 g?

6.4502 Signup and view all the answers

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

-3.27 x 10^4 Signup and view all the answers

Match the following quantities with their corresponding calculations:

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 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?

-318 kJ/mol (C) Signup and view all the answers

Exothermic reactions absorb energy from their surroundings.

False (B) Signup and view all the answers

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

Al2O3(s) and 3 Ni(l) Signup and view all the answers

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

released Signup and view all the answers

Match the following substances with their role in the reaction:

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

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

-29.2 kJ/mol (A) Signup and view all the answers

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

True (A) Signup and view all the answers

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

4.52 kg Signup and view all the answers

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

-1275.8 Signup and view all the answers

Match the following components to their respective roles:

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

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

-1 301.1 kJ/mol (D) Signup and view all the answers

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

True (A) Signup and view all the answers

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

5 Signup and view all the answers

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

oxygen Signup and view all the answers

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

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

Exothermic Reaction

A chemical reaction where energy is released into the surroundings, resulting in a decrease in the system's energy content.

Endothermic Reaction

A chemical reaction where energy is absorbed from the surroundings, resulting in an increase in the system's energy content.

Enthalpy

The total internal energy of a chemical system, including both kinetic energy (energy of motion) and potential energy (stored energy).

Enthalpy Change (ΔH)

The change in enthalpy (heat content) during a chemical reaction. It represents the heat absorbed or released by the system.