Experiment: Gravimetric Determination of Phosphorus in Fertilizer Samples

1. Can NH4Cl be used as a substitute to precipitate the phosphorus in the sample? Why or why not?
- I think, NH4Cl can be used although I'm not quite sure if Cl- ions have some effects to the precipitation process. Am I right? Can NH4Cl be used for homogeneous precipitation?

I am not familiar with a homogeneous pptn method for the determination of P in fertilizer. The gravimetric method most often used in my experience is the pptn of MgNH4PO4*6H2O but that isn't done homogeneously unless your procedure does that. The NH4Cl in your question might be used to help buffer the solution for solutions that are too acid or too basic do not ppt the desired substance. You may want to clarify your question by posting a summary of the procedure but from what I know about P determinations, I don't think NH4Cl can be used as a substitute to ppt P.

I think it isn't possible because....


How much heat is evolved if 2 moles of C3H8 is burned?

Based on the information provided, it is not clear if NH4Cl can be used as a substitute for precipitating phosphorus in the fertilizer samples. The preferred method for gravimetric determination of phosphorus in fertilizer samples is the precipitation of MgNH4PO4*6H2O. This method is not usually done homogeneously unless specified in the procedure.

NH4Cl may be used in this context to help buffer the solution, especially if the solution is too acidic or basic, as the pH can affect the precipitation of the desired substance. However, it is important to note that NH4Cl itself may not directly precipitate phosphorus. To obtain a more accurate answer, further clarification on the specific procedure being used is required.

To determine if NH4Cl can be used as a substitute to precipitate phosphorus in fertilizer samples, we need to consider the properties and behavior of NH4Cl and its effect on the precipitation process.

To start, let's understand the basic principles of gravimetric determination. Gravimetric analysis involves the separation and quantification of a desired substance by precipitating it from a solution and weighing the precipitate. This method is often used for its accuracy and precision.

In the case of phosphorus determination, the commonly used precipitant is MgNH4PO4*6H2O (magnesium ammonium phosphate hexahydrate). This precipitate is formed by adding ammonium phosphate or ammonium molybdate to the sample solution containing phosphorus. The resulting precipitate is then collected, dried, and weighed to determine the phosphorus content.

Now, let's consider NH4Cl as a possible substitute. NH4Cl itself does not form a precipitate with phosphorus under typical conditions. However, NH4Cl can be used in certain cases to adjust the pH or provide buffering in the sample solution.

For example, if the sample solution is too acidic, NH4Cl can be added to raise the pH and optimize the conditions for the formation of the desired precipitate. Similarly, if the solution is too basic, NH4Cl can act as a buffer to maintain the pH within the suitable range for precipitation.

In summary, NH4Cl can be used as an auxiliary reagent in the gravimetric determination of phosphorus to adjust the pH or provide buffering effects. However, it cannot be used as a direct substitute for the precipitant (such as MgNH4PO4*6H2O) itself. The actual precipitation of phosphorus usually requires specific reagents designed for that purpose.

In your original question, you asked about homogeneous precipitation. Homogeneous precipitation refers to the formation of a precipitate in a solution without any solid particles present. This is typically achieved by carefully controlling reaction conditions, such as temperature, concentration, and pH. However, in the context of gravimetric determination of phosphorus, homogeneous precipitation is not commonly used.

To summarize, while NH4Cl can be used in the gravimetric determination of phosphorus for adjusting pH or providing buffering effects, it cannot be used as a substitute for the precipitant itself. The actual precipitation process often involves specific reagents designed for the purpose of phosphorus determination. So, NH4Cl would not be used for homogeneous precipitation in this experiment.