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:
0.3267 M
Explanation:
To solve this problem, first we calculate how many moles of Mn(ClO₄)₂ are contained in 23.640 g of Mn(ClO₄)₂·6H₂O.
Keep in mind that the crystals of Mn(ClO₄)₂ are hydrated, and <em>we need to consider those six water molecules when calculating the molar mass of the crystals</em>.
Molar mass of Mn(ClO₄)₂·6H₂O = 54.94 + (35.45+16*4)*2 + 6*18 = 361.84 g/mol
Now we <u>proceed to calculate</u>:
- 23.640 g Mn(ClO₄)₂·6H₂O ÷ 361.84 g/mol = 0.0653 mol Mn(ClO₄)₂·6H₂O = mol Mn(ClO₄)₂
Now we divide the moles by the volume, to <u>calculate molarity</u>:
- 200 mL⇒ 200/1000 = 0.200 L
- 0.0653 mol Mn(ClO₄)₂ / 0.200 L = 0.3267 M
Answer:Ionic compounds form when positive and negative ions share electrons and form an ionic bond. ... The positive ion, called a cation, is listed first in an ionic compound formula, followed by the negative ion, called an anion. A balanced formula has a neutral electrical charge or net charge of zero.
Explanation:Simple ions:
Perchlorate ClO4- IO3-
Chlorate ClO3- BrO3-
Chlorite ClO2-
Hypochlorite OCl- OBr-
Answer:
The key difference between empirical and molecular formulas is that an empirical formula only gives the simplest ratio of atom whereas a molecular formula gives the exact number of each atom in a molecule.
The valves stop the blood from flowing backwards
