Acid has a pH below 7 while water has a pH of 7. A strong acid with a pH of roughly 3, HCl is. Water gets more acidic and loses pH in the range of 4-5 when HCl is added to it.
<h3>What is pH?</h3>
A substance's pH is a gauge of how basic or acidic it is. It is a measurement of the amount of H+ present in the solution. It is equivalent to the negative logarithm of the concentration of H+ ions mathematically.
A solution is acidic if its pH value is less than 7, and basic if it is greater than 7. Acids have a lower pH because they contain more H+ ions. Strong acid hydrochloric acid has a pH between 2 and 3.
Water has no charge. Water becomes acidic in pH if any acid is introduced. Therefore, if HCl is given to water, the pH of the water will change to 3-5 depending on the acid content.
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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>
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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>
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