Answer:
This exemplifies the agricultural role of water.
Explanation:
Correct Question:
A chemist measures the enthalpy change ΔH during the following reaction: Fe(s) + 2HCl(g)-->FeCl2(s) + H2 ΔH=-157.0 kJ. Use this information to complete the table below. Round each of your answers to the nearest kJ/mol
Answer:
-314 kJ
+628 kJ
+157 kJ
Explanation:
The enthalpy change of a reaction measures the amount of heat that is lost or gained by it. If ΔH >0 the heat is gained, and the reaction is called endothermic, if ΔH<0, the heat is lost, and the reaction is called exothermic.
If the reaction is inverted, the value of ΔH is inverted too (the opposite endothermic reaction is exothermic), and if the reaction is multiplied by a constant, ΔH will be multiplied by it too.
1) 2Fe(s) + 4HCl --> 2FeCl2(s) + 2H2(g)
This reaction is the product of the given reaction by 2, so
ΔH = 2*(-157) = -314 kJ
2) 4FeCl2(s) + 4H2(g) --> 4Fe(s) + 8HCl(g)
This reaction is the inverted reaction given multiplied by 4, so
ΔH = 4*(157) = +628 kJ
3) FeCl2(s) + H2(g) --> Fe(s) + 2HCl
This reaction is the inverted reaction given, so
ΔH = +157 kJ
__ KClO₃ → __ KCl + __ O₂
Left Side:
1 K
1 Cl
3 O
Right Side:
1 K
1 Cl
2 O
Since the least common multiple of 3 and 2 is 6, we need to multiply the compound with 2 oxygen by 3 and the compound with 3 oxygen by 2.
This gives us 2KClO₃ → __ KCl + 3O₂.
However, this equation is still not balanced.
Left Side:
2 K
2 Cl
6 O
Right Side:
1 K
1 Cl
6 O
In order to balance the K and Cl, we need to multiply the KCl compound on the right side by 2.
2KClO₃ → 2KCl + 3O₂
Based upon Max Planck's theory of black-body radiation, Einstein theorized that the energy in each quantum of light was equal to the frequency multiplied by a constant, later called Planck's constant. A photon above a threshold frequency has the required energy to eject a single electron, creating the observed effect.
(a) Matter cannot be created and destroyed by a chemical reaction.
Explanation:
(a) Matter cannot be created and destroyed by a chemical reaction. (correct)
The number and type of atoms entering the chemical reaction are the same with the number and type of atoms leaving the chemical reaction.
(b) The reactants are the same substance as the products. (wrong)
You may see in the reaction that we have as reactants zinc and hydrochloric acid which react to form the products, zinc chloride and hydrogen.
(c) The number of molecules in the reactants are equal to the number of molecules in the products. (wrong)
As reactants we have 2 hydrochloric acid (HCl) molecules and as products 1 hydrogen (H₂) molecule. Zn is a metal and ZnCl is a salt.
(d) The atoms on the reactants side are changed into different atoms on the products side. (wrong)
The number and type of atoms entering the chemical reaction are the same with the number and type of atoms leaving the chemical reaction.
Learn more about:
balancing chemical equations
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