After a chemical change, the substance always changes. It's only after a physical change that the substance does not change. Hope I helped :)
Answer:
Answer 'A'
Explanation:
In general, if the Σmolar volumes(g) reactants ≠ Σmolar volumes(g) products, a change in atmospheric pressure will shift the reaction equilibrium. If the pressure is increased, the rxn will shift toward the LOWER molar volume side of the rxn or if the pressure is decreased the rxn will shift toward the HIGHER molar volume side. For the reaction N₂O₄(g) ⇄ 2NO₂(g), Vm(N₂O₄(g)) < Vm(NO₂(g)) so, a decrease in atmospheric pressure would shift rxn toward the NO₂(g) side of the equation increasing the moles of NO₂(g). Also, note that if the Σmolar volumes(g) reactants = Σmolar volumes(g) products, no shift in equilibrium will occur regardless of changes in atmospheric pressure.
A link is a part of a chain and an atom is a part of a molecule. It is also a part of a compound. Your answer should be molecule and/or compound
18. <span>Answer is </span>
A<span>
<span>Since the enthalpy of reaction is positive, the
forward reaction is<span> an endothermic reaction which means the energy
is gained from the surrounding to happen the reaction. If the temperature
decreases, according to the </span></span>Le Chatelier's principle, the system tries to become equilibrium
by increasing temperature. Since forward reaction is endothermic (because of
the bond breaking), the backward reaction is exothermic (because of the bond
making) which releases the energy to the surroundings. This makes the increase
of temperature. So if the backward reaction is promoted because of the decrease
of temperature, then the concentration of H</span><span>₂ will decrease.</span>
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19. Answer is A.
The reactant side
has 2 moles/molecules of reactants and the product side has 4 moles/molecules
of products which come from 1 N₂(g) and 3 H₂<span>(g). If the pressure is reduced in the system, according to the Le Chatelier's principle, the
system tries to increase the pressure. </span><span>Hence, forward
reaction is promoted because of the higher number
of molecules in product side. If the forward reaction is promoted, the
concentration of NH</span>₃(g) will decreased.
<span>20. </span>Answer is C.
If the concentration
of reactant is increased in the
system, according to the Le Chatelier's principle, the system tries
to reduce the concentration of that reactant. So if NH₃(g) concentration
is increased, then to be equilibrium, the forward reaction will be promoted.
Then the concentration of N₂<span>(g) will increase.</span>
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