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>
<span>
</span>
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>
<span> </span>
Carbonic acid
dissolves limestone and other rocks. This is an example of chemical erosion. An
example is in the caves. Caves are formed where rainwater as it falls
through the atmosphere absorbs carbon dioxide. The carbon dioxide makes the
rain acidic to react it with the limestone bedrock. The rainwater is absorbed
by the soil into the ground. Then as it enters through the soil, the rainwater
will absorb more carbon dioxide that is produced by the decomposers. The carbon
dioxide with water reacts to form carbonic acid. The carbonic acid will react
to limestone and dissolves it slowly. As the space become larger, water can
enter into it.
Answer:
A chemical equation can be described as a symbolic representation of a chemical reaction. It can be written in the form of words or symbols.
The following chemical reaction can be completed as :
Na2SO4·10H2O + 2C = Na2S + 10H2O + 2CO2
Sodium Sulfate Decahydrate + Diamond = Sodium Sulfide + Water + Carbon Dioxide
The products of the reaction are:
- Sodium Sulfide (Na2S)
- Water (H2O)
Can’t have anything in Detroit
Answer:
two north poles and two south poles
Explanation:
A single magnet has a north pole and a south pole. If it is broken into two pieces, then each of the two pieces will have a north pole and a south pole.
No matter how many times or into how many pieces a magnet is broken, the resulting pieces will have two poles each.
