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>
Sugar, on the other hand, is composed of carbon, oxygen, and hydrogen and has covalent bonds. A salt molecule is made up of one sodium atom and one chlorine atom.
Answer:
C₃H₉N
Explanation:
The empirical formula of a compound is the fundamental and basic possible formula that shows the mole ratio of the atoms of each element in a molecule of the compound.
mole ratio of carbon = 60.94/12 = 5.078
mole ratio of hydrogen = 15.36/1 = 15.36
mole ratio of nitrogen = 23.70/14 = 1.693
Now; we will divide by the smallest value
So; carbon = 5.078/1.693 = 2.99 ≅ 3.0
hydrogen = 15.36/1.693 = 9.07 ≅ 9.0
nitrogen = 1.693/1.693 = 1 ≅ 1
Thus, the empirical formula is = C₃H₉N
