Question

1-Propanol is combusted to provide heat. The reaction and the enthalpy for the reaction are shown below. C3H7OH(l)+4.5O2(g)->3CO2(g)+4H2O(l)deltaH=-2,021kJ Below is a list of sentences that describe a chemical reaction. Choose all of the sentences that apply to the above reaction. Check all that apply. View Available Hint(s) Check all that apply. The enthalpy for 2C3H7OH(l)+9O2(g)->6CO2(g)+8H2O(l) is 4,042 kJ This process is endothermic. This process is exothermic. The enthalpy for 2C3H7OH(l)+9O2(g)->6CO2(g)+8H2O(l) is -4,042 kJ The enthalpy for 2C3H7OH(l)+9O2(g)->6CO2(g)+8H2O(l) is 2,021 kJ This chemical reaction transfers heat from the surroundings to the system. The enthalpy for 2C3H7OH(g)+9O2(g)->6CO2(g)+8H2O(l) is -2,021 kJ This chemical reaction transfers heat from the system to the surroundings.

Answer 1

Answer: The enthalpy for
`2C_3H_7OH(l)+9O_2(g)\rightarrow 6CO_2(g)+8H_2O(l)` is 4,042 kJ , This process is exothermic and This chemical reaction transfers heat from the system to the surroundings.

Explanation: Endothermic reactions are those reactions in which heat is absorbed by the system and thus the heat released by the surroundings is transferred to the system. For endothermic reactions , the sign of enthalpy change is positive.

Exothermic reactions are those reactions in which heat is released by the system and thus the heat released by the system is transferred to the surroundings. For exothermic reactions , the sign of enthalpy change is negative.

`C_3H_7OH(l)+4.5O_2(g)\rightarrow 3CO_2(g)+4H_2O(l)`
`\Delta H=-2,021kJ`

1 mole of
`C_3H_7OH` undergoes combustion to release 2,021kJ of heat.

`2C_3H_7OH(l)+9O_2(g)\rightarrow 6CO_2(g)+8H_2O(l)`

Thus 2 moles of
`C_3H_7OH` undergoes combustion to release=
`( 2,021kJ)/(1)* 2=4042kJ` of heat.

Answer 2

Answers are:

1) This process is exothermic.

2) The enthalpy for 2C3H7OH(l)+9O2(g)->6CO2(g)+8H2O(l) is -4,042 kJ.

3) This chemical reaction transfers heat from the system to the surroundings.

There are two types of thermochemical reactions:

1) endothermic reaction (chemical reaction that absorbs more energy than it releases).

For example, ΔH(reaction) = 150 kJ/mol; this is endothermic reaction.

2) exothermic reaction (chemical reaction that releases more energy than it absorbs).

The change in enthalpy = the total bonding energy for the products of a reaction - the bonding energy of the reactants.

When ΔH is negative, that is exothermic reaction.