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>
Answer:
Option (E) is correct
Explanation:
Solubility equilibrium of
is given as follows-

Hence, if solubility of
is S (M) then-
and ![[IO_{3}^{-}]=2S(M)](https://tex.z-dn.net/?f=%5BIO_%7B3%7D%5E%7B-%7D%5D%3D2S%28M%29)
Where species under third bracket represent equilibrium concentrations
So, solubility product of
, ![K_{sp}=[Pb^{2+}][IO_{3}^{-}]^{2}](https://tex.z-dn.net/?f=K_%7Bsp%7D%3D%5BPb%5E%7B2%2B%7D%5D%5BIO_%7B3%7D%5E%7B-%7D%5D%5E%7B2%7D)
Here, ![[Pb^{2+}]=S(M)=5.0\times 10^{-5}M](https://tex.z-dn.net/?f=%5BPb%5E%7B2%2B%7D%5D%3DS%28M%29%3D5.0%5Ctimes%2010%5E%7B-5%7DM)
So, ![[IO_{3}^{-}]=2S(M)=(2\times 5.0\times 10^{-5})M=1.0\times 10^{-4}M](https://tex.z-dn.net/?f=%5BIO_%7B3%7D%5E%7B-%7D%5D%3D2S%28M%29%3D%282%5Ctimes%205.0%5Ctimes%2010%5E%7B-5%7D%29M%3D1.0%5Ctimes%2010%5E%7B-4%7DM)
So, 
Hence option (E) is correct
The answer would be choice B because the energy decreased by 20 J
Answer:
A wave is a disturbance that carries energy from one place to another through matter and space. When we through a stone or a pebble in calm water, then the particles of water moves up and down and this process continues for some time. This implies that there is a disturbance produced in water.
Explanation:
Answer:
92.04%
Explanation:
Given:
Mass of CO₂ obtained = 53.0 grams
Mass of calcium carbonate heated = 1.31 grams
Now,
the molar mass of the calcium carbonate = 100.08 grams
The number of moles heated in the problem = Mass / Molar mass
= (1.31 grams) / (100.08 grams/moles)
= 0.013088 moles
now,
1 mol of calcium carbonate yields 1 mol of CO₂
thus,
0.013088 moles of calcium carbonate will yield = 0.013088 mol of CO₂
now,
Theoretical mass of 0.013088 moles of CO₂ will be
= Number of moles × Molar mass of CO₂
= 0.013088 × 44 = 0.5758 grams
Thus, the percent yield for this reaction = 
or
the percent yield for this reaction = 
or
the percent yield for this reaction = 92.04%