Answer:
-586.56 kJ/mol is the standard enthalpy of the 3rd reaction.
Explanation:
...[1]
...[2]
..[3]
The unknown standard enthalpy of third reaction can be calculated by using Hess's law:
The law states that 'the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps'.
[2] - 2 × [1] = [3]



The standard enthalpy of the 3rd reaction is -586.56 kJ/mol.The negative sign indicates that energy is released during this reaction.
Answer:
Because one calorie is equal to 4.18 J, it takes 4.18 J to raise the temperature of one gram of water by 1°C. In joules, water's specific heat is 4.18 J per gram per °C. If you look at the specific heat graph shown below, you will see that 4.18 is an unusually large value.
The mass of the piece of wood is 35.58 g.
Joule = M × T × C
Where, M = mass
T = change in temperature(42C-23C=19 C)
C = specific heat capacity = 1.716 joules/gram
Substituting the values in the equation,
1160 = M × 19 × 1.716
M = 1160/32.604 = 35.58 g
Therefore, the mass of the piece of wood = 35.58 g
<h3>What is meant by specific heat capacity?</h3>
A material's specific heat capacity, which is defined as its heat capacity divided by its mass, determines how much energy is required to increase a gram's temperature by one degree Celsius (or one Kelvin)
<h3>What is mass?</h3>
Mass is the quantity of matter in a physical body.
To learn more about specific heat capacity visit:
brainly.com/question/1747943
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Noble gasses I think I could be wrong tho