A 1 -liter 10x stock solution of SDS-running buffer was made in preparation for

Question

A 1 -liter 10x stock solution of SDS-running buffer was made in preparation for this week's lab. SDS-buffer is composed of SDS, glycine, and Tris base (tris(hydroxymethyl)aminomethane, (HOCH_2)_3CNH_2), a commonly used buffer in biochemistry and molecular biology. The 10x solution has a 1% concentration of SDS (MW 288.38). What is the molarity of the SDS in the 1x running buffer? (The 10x stock is made at a concentration that is ten times that of the concentration that is to be used in the procedure.)

Explanation / Answer

Molarity od 10X strock = moles of SDS / 1L solution

concentration is 1% which means that 1gm is present in 100mL solution

Moles of SDS = 1gm/288.38g/mol = 3.47*10^-3 mol

Number of moles present in 1000mL = 3.47*10^-3 mol *100mL/10mL = 3.47 *10^-2 mol

Molarity = 3.47*10^-2 M

The running buffer solution is 10 times dilute.

So, molarity of the running buffer is 3.47*10^-3 M

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