Which trials should you use to determine the concentration of the hydrochloric acid? (this is about titrations)
Answers
Answer:
Titration of Hydrochloric Acid with Sodium Hydroxide
Revision SP12 RBR Page 1 of 7
Cautions: Hydrochloric acid solution is a strong acid. Sodium hydroxide solution is a strong
base. Both are harmful to skin and eyes. Affected areas should be washed thoroughly with
copious amounts of water.
Purpose: The purpose of this lab is to determine the concentration of a hydrochloric acid
solution using acid‐base titration.
Background: Titration is a technique that chemists use to determine the unknown
concentration of a known solution (we know what chemical is dissolved, but not how much in a
solution). Because we know what the chemical is, we know how it will react with other
chemicals and we can use that reaction to determine the concentration of the solution by
measuring the formation of product(s). In the case of an unknown concentration of acid, we
can use a known concentration of hydroxide base. This type of reaction is a neutralization
reaction, where salt and water are products of the reaction:
Acid + Base Salt + H2O
We can use a pH indicator, a chemical that changes color depending on the pH, to show
us when the reaction has completely neutralized. This point, where all acid was consumed and
there is no excess of base, is called the equivalence point. We can use this equivalence point to
determine the initial concentration of acid using a series of calculations. The goal of the
titration is to get as close as possible to the equivalence point by careful addition of the base;
this will ensure the calculated acid concentration is as close to the true value as possible. You
will do three titrations and average the trials.
The terms below will help you understand the terminology used throughout the
experiment:
Titrant—the solution of known concentration is also called the standardized solution. In
this lab, the titrant is sodium hydroxide solution.
Buret—a long, cylindrical piece of glass that can be used to determine small, accurate
quantities of a solution. A buret is controlled by a stopcock, a white Teflon piece that
can be turned to deliver the solution. The markings on the buret are such that you must
subtract the initial reading (where the titrant level is initially) from the final reading to
determine the volume of base delivered. The buret measures 2 digits after the decimal
point accurately.
Volumetric pipette/pipette bulb—a thin glass tube with only one marking used to
measure a very specific volume of liquid. You will use a pipette bulb to draw the liquid
into the pipette
Explanation: