concentration of an unknown HCl solution and a portion of the lab grade will be
ID: 1015645 • Letter: C
Question
concentration of an unknown HCl solution and a portion of the lab grade will be based on your accuracy. Define and explain titration. In the experimental procedure, the buret is prepared by pre-rinsing with NaOH and discarding the rinse. Explain the purpose of pre-rinsing the buret with NaOH solution and identify what errors might be introduced if prerinsing is not performed before a titration. Write the complete balanced equation for the neutralization reaction of KHC_8H_4O_4 (KHP) with NaOH. KHP is a weak monoprotic acid. Determine the amount of solid KHP that would need to be measured out so that a titration will take approximately 15 mL of 0.1 M NaOH to reach the equivalence point. Show your work and units. Write the complete balanced equation for the neutralization reaction of HCl with NaOH.Explanation / Answer
1. Titration is a technique in which the known solution is titrated with unknown solution to know its concentration. Suppose we have an acid and a base. We know the concentration of acid, which means that we know the moles of acid being used. Those moles of acid will be neutralized by equal moles of base. So, we can calculate the concentration of base. This method is not only valid for acids and bases. Other reactions can also be used to determine the concentration of unknown compound.
2. The prerinsing is done with NaOH solution because if it done with water, then when we add NaOH to the buret for titration, it will lead to dilution due to left over water droplets. Thhis will alter the reading of volume of NaOH used and will lead to wrong measurements.
3. KHC8H4O4 + NaOH ----------> KC8H4O4-Na+ + H2O
KHP is a weak monoprotic acid, so on titration with NaOH, the proton will be replaced by Na+.
4. NaOH used:
Volume = 15 ml = 0.015 L
concentration = 0.1 M
Moles of NaOH = concentration*volume = 0.1*0.015 = 0.0015 mol
In the reaction, we saw that equal moles of NaOH will be used for titration of KHP.
moles of KHP = moles of NaOH = 0.0015 mol
Molar mass of KHP = 204 g/mol
Mass of KHP = molar mass*moles = 204*.0015 = 0.306 g
Amount of solid KHP = 0.306 g
5. HCl + NaOH ------> Na+Cl- + H2O
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