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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: thomasc93 on March 13, 2021, 07:23:15 PM

Title: Determining chromate conc via spectrophotometry
Post by: thomasc93 on March 13, 2021, 07:23:15 PM
Just curious, but when we were doing a lab calculating Ksp of Ag2CrO4, we determined the concentration of chromate in solution with a spectrophotometer, and as such, we first had to make a calibration curve based on the absorbances of chromate solutions of known concentration.

When making our solutions of known concentration, we took incremental volumes of 0.0024M potassium chromate and diluted each with 0.25M sodium nitrate solution to reach 100ml of standardized samples of known concentration.

Why did we dilute the potassium chromate with sodium nitrate? Why not use distilled water?
Title: Re: Determining chromate conc via spectrophotometry
Post by: chenbeier on March 14, 2021, 04:23:17 AM
What is the matrix to determine the silver chromate? Any Nitrate in use.
Title: Re: Determining chromate conc via spectrophotometry
Post by: thomasc93 on March 14, 2021, 09:39:25 AM
Quote from: chenbeier on March 14, 2021, 04:23:17 AM
What is the matrix to determine the silver chromate? Any Nitrate in use.

Thanks for your reply! Interesting... Could you elaborate more on the effect of nitrate has as a matrix? We don't cover really any details of the analytical methods we use in my gen chem II class, so I really have zero knowledge of how a sample's matrix could affect the spectrophotometry measurement, especially when the sodium nitrate solution and water would both be colorless matrices.

Does it promote/increase solubility of the silver chromate?