Data Analysis:

Table 1: Determination of the amount of sulfate in the unknown

The above table was the results and calculations from the following lab, and were used to find the percent of sulfate in the sample. 

Table 2: Possible unknowns

To calculate the mass of the dried precipitate, the mass of the crucible with dried precipitate was subtracted from the mass of the empty crucible.

The number of moles of precipitate was calculated by using its mass and formula weight.

The mass of the sulfate ions was calculated from the number of moles of sulfate ions.

The theoretical percentage of sulfate content in the unknown sulfate sample was calculated by using the mass of sulfate ions and total mass of the sample.

Based on the calculations of the percentage of the unknown sample and table 2 above, the unknown sample solution is Na.

The compound based on results is  

The percent error is based on the experimental value of the percent sulfate content of the sample and the percent sulfate content of the proposed unknown.

Conclusion:

Based on the results, it can be determined that the unknown sulfate compound was Na2SO4.  The actual sulfate content of Na2SO4 is 68% and from the results of the experiment the percentage of sulfate was 65.66%.  The percent error came out to be only 3.4%, making Na2SO4 the closest possible unknown sulfate.  Some sources of error could of been from not heating the AgNO3 long enough, having residue on the tongs from poking the precipitate during heating, and not heating the precipitate long enough.  This would cause the results to be higher.