The molecular weight of Quercetin hydrate is 302.24, on an anhydrous basis. The water content must be considered and is variable from lot to lot. The solubility, pKa, LogP, and absorption maximum are not determined. According to Drugbank the solubility in water is 261 ug/mL, the acidic pKa is 6.38 and the basic pKa is -4, and the LogP is 1.81 (per ALOGPS) and 2.16 (per Chemaxon). The absorbance maximum is not listed.
See the link below for further information from Drugbank:
https://go.drugbank.com/drugs/DB04216
See the publication below for additional information on absorbance of Quercetin:
https://www.jocpr.com/articles/determination-of-quercetin-by-uv-spectroscopy-as-quality-control-parameter-in-herbal-plant-cocculus-hirsutus.pdf