chem questions on fertiliser

[depressedchild]

why is each of the elements nitrogen, phosphorus, sulfur and iron included in lawn food?

what distinguishes gravimetric analysis from other forms of analysis?

briefly describe the process of volumetric analysis
explain the chemical principle involved in spectroscopic techniques in general and specifically in colorimetry.

[misaki]

Gravimetric analysis is based on the measurements of mass, which relates to weighing and usually to filtering and drying of precipitates (which does not happen in volumetric analysis.)

Also, you can follow these steps to perform a volumetric analysis.
Lets take a standard solution of NaOH at 14.70 ml and 25 ml of HCL with an unknown concentration. HCl is what you will be standardising.

1. Rinse all equipment with water

2. Rinse burette (HCl) and pipette(NaOH) with appropriate solutions.

3. Accurately pipette 20 ml of unknown (HCl) into conical flask + add for drops of the appropriate indictator.

4. Fill the burrette with standard solution (NaOH) and take the initial reading on the burrette.

5. Titrate until the end point. You will notice the end point as the color will change, colors depending on which indicator you used.

6. Repeat until 3 cocordant results are obtained. ( for accurate results)