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Acid and alkali chemical in the test question answer questions answers


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									Acid and alkali chemical in the test FAQ answer questions

  in chemistry exam answer
. Why have some similar acid or alkali chemical nature?
: The acid or alkali solution, such as hydrochloric acid, sulfuric acid, sodium hydroxide and
calcium hydroxide solution can conduct electricity, which shows the existence of these charged
particles in solution, such as HCl in water solution from the H + and Cl-, H2SO4 in water will
dissociate H + and SO42-; NaOH dissociate in water Na + and OH-, Ca (OH) 2 solution in water
from the Ca2 + and OH-. We can see the acid dissociation of the H +, while the base can be
dissociated OH-, that whilst there are acid or alkali, but the solution contains the same elements
are H + or OH-, so they have some similar chemical properties.
  2. Those who generate the reaction of salt and water are in, and response?
: No.. Because of and response is defined as "the role of acid and alkali salts and water response
generated." Apart from the role of acid and alkali salt and water that can be generated in the
chemical properties of acids and bases, we also learned to produce salt and water through the
reaction, as some non-metallic oxides with alkali reaction (2NaOH + CO2 = Na2CO3 + H2O); a
These metal oxides and acid reaction (CaO +2 HCl = CaCl2 + H2O) and so on, but these are not
in and response.
  3.pH value of less than 7, equal to 7, greater than 7 the solution diluted with water, the pH value
of what changes will occur?
  A: pH value of less than 7, the solution is acidic solution, if diluted with water, solution will
become diluted, the concentration of smaller, less followed the acid solution, pH value increased,
but no more than 7, only will be infinitely close to 7. The solution pH value above 7 is alkaline,
pH value decreased empathy, but no more than 7, only infinitely close to 7. solution pH value is
equal to 7, were neutral, or neutral solution diluted, so its pH constant, or equal to 7.
  4. Litmus test solution and ferric hydroxide phenolphthalein test solution will color you
: Not at all. Acid-base indicator is only encountered when the acid solution or alkali solution will
change color. Most of the acids are soluble in water, and base is different, only a few base is able
to dissolve in water, such as: potassium hydroxide (KOH), sodium hydroxide (NaOH), barium
hydroxide 〔 Ba (OH) 2) and calcium hydroxide 〔 Ca (OH) 2 〕 . When the litmus and
phenolphthalein solution will encounter their color, while iron hydroxide 〔Fe (OH) 3〕 is not
soluble in water, such as alkali, so do not change color litmus and phenolphthalein.
  5. Long-term exposure to sulfuric acid and placed in concentrated hydrochloric acid, why is the
mass fraction of solute will decrease?
: Because the concentrated sulfuric acid with water absorption, long-term exposure to air in place
is easy to absorb moisture, solvent quality increased, solution quality increases, the solute
concentration decreases; concentrated hydrochloric acid are volatile, volatile a solute, solute
reduce the quality, the solute mass fraction decreased.
  6. Using pH test strips for the Determination of pH, the ability to strip water wet?
  A: You can not. After wetting solution is equivalent to diluted acid and alkaline are weakened.
Determination of the acid solution after wetting the pH value of solution pH than the actual value
is too large, while the alkaline pH value of solution pH value than the actual solution is smaller.
  7. "Acid solution" and "acidic solution", "alkaline solution" and "alkaline solution" thing?
: No.. Acid solution refers only to the solute for the acid solution must belong to the acidic
solution; such as hydrochloric acid, sulfuric acid. However, the solution of certain salts, such as
NaHSO4 also acidic, but does not belong acid solution; alkali solution means the solution of
soluble alkali (KOH, NaOH, Ca (OH) 2, Ba (OH) 2, NH3 · H2O), must belong to the alkaline
solution; but the solution of certain salts such as Na2CO3 solution also significantly alkaline,
alkaline solution does not belong.
  8. We normally say seasoning salt and chemical salt is one thing on it?
: No.. We normally used in the kitchen seasoning salt refers to salt, which is sodium chloride
(NaCl), while the salt is chemically referred to in the name of a class of compounds, as acids,
alkalis, as both of these compounds in water ionization of metal ions and ion, like calcium
chloride (CaCl2), sodium carbonate (Na2CO3), potassium sulfate (K2SO4) belong to the salts.
  9. How to determine the NaOH solution and the reaction between hydrochloric acid just
completely done?
: We can use the indicators to be completed, adding about 10ml in a beaker the sodium hydroxide
solution, instillation of 2 to 3 drops of phenolphthalein solution. Then slowly drops hydrochloric
acid dropper and drip edge side constantly stirring the solution to the solution color from red to
colorless is just up, then sodium hydroxide and hydrochloric acid just complete the reaction.
  10. Why solid sodium hydroxide, lime sealed?
  A: Solid sodium hydroxide will absorb water and carbon dioxide in the air, place the following
reaction CO2 +2 NaOH = Na2CO3 + H2O, will deliquescence, degenerate. Similarly, there are
lime reaction CaO + H2O = Ca (OH) 2, CO2 + Ca (OH) 2 = CaCO3 ↓ + H2O twisted, so both
need sealed.

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