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:
The density of the swimmer is 0.0342 lbm/in3.
This value makes sense as the density of the body is very similar to the water.
Explanation:
If the swimmers is floating, the weight of the swimmer must be equal to the upward buoyant force.
We can express the weight force as the product of density and volume of the swimmer.
Then
It makes sense as the density of the body is very similar to the water.
KOH is a strong base and HBr is a strong acid and completely dissociates.
The balanced equation for the reaction is;
KOH + HBr ---> KBr + H₂O
Stoichiometry of acid to base is 1:1
The number of KOH moles reacted - 0.50 M / 1000 mL/L x 48.0 mL = 0.024 mol
number of HBr moles reacted - 0.25 M/ 1000 mL/L x 96.0 mL = 0.024 mol
the number of H⁺ ions are equal to number of OH⁻ ions.
Then the solution is neutral.
pH of neutral solutions at 25 °C is 7.
Therefore pH is 7
