Standard Base and Unknown Acid Obtain approximately 60 mL of the unknown acid so

Question

Standard Base and Unknown Acid Obtain approximately 60 mL of the unknown acid solution in a clean, dry 100mL or 150mL beaker. Label this flask as "Unknown Acid" Obtain approximately 35 mL of the RNH2 TRIS standard base solution in a clean, dry 100 or 150-mL beaker. Label the beaker as "Standard Base". Do NOT take more than 35mL, which should be enough for the entire experiment. If you need more TRIS, you can always obtain it later during the experiment. Record the exact concentration including the uncertainty of the standard base in your lab notebook.

Explanation / Answer

Tris(hydroxymethyl)aminomethane or (THAM) is a weak base which is used to prepare buffers by mixing it with HCl. The reaction can be given as:

RNH2 + HCl RNH3Cl

A 35ml of 2M RNH2 TRIS solution is titrated with 60ml of unknown concentration of acid solution sample.

Given: Molarity of RNH2 TRIS = 2M   

Volume of RHN2 TRIS used = 35ml = 0.035L

volume of acid used = 60ml = 0.060 L

Concentration of acid = ?

Step by step solution is given below:

Step 1: Determine the number of moles of RNH2 TRIS in solution

number of moles = molarity x volume

Number of moles of RNH2 TRIS = 2M x 0.035L = 0.07 mol

Step 2: Determine number of moles of acid in solution

When base neutralizes acid, then number of moles of acid = number of moles of base

Therefore number of moles of acid = 0.07mol

Step 3: calculate concentration of acid

Molarity = 0.07mol/ 0.060L = 1.16M

Concentration of acid = 1.16M

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