Question

CHROMIC ACID OXIDATION Pre Lab Questions the amounts of materials that will be used from the experimental section above) H2SO4 + Na2Cr207 2H20- H2O, A Molecular Weight Theoretical yield amount moles on (if applicable) Equivalents 2. Look up the melting point for p-nitrobenzoic acid and record the reference. 3. What color change is expected to be observed in the reaction? Explain why.

Answer 1

Date Page molecular weight Na₂C%₂07.2H₂O 137 g/mol. selain 297 g/mol Amount 0.140gm sila 0.4oogm. moles. 0.00102 0.00134 density / concn. Equivalents 0.76 Calculation of moles: - moles 0.140 gm 137 g/mol 137 = 0.00102 (2 moles = 0.4oogm. = oroo/34 297g/mol * Equivalents ;- O consider p-nitrotoluenc as a 0.76 equivalent 0.00102 (moles of p-nitrotoluene) 1600134 c moles of sodium dichromate dihydrate) = 0.76 eauovalent of p-nitrotoleene

- 0.00134 oroolo2 (moles of sodium dichromate dinydrate) Cmoles of p-nitrotoluene) = 1.3 equivalent of sodium dichromate dihydrate The pratical yield of p-nitro benzoic acid on P-nitrotolucna p-nitrobenzoic acid C₂ H₂ NO₂ 1 C H & NOY 137 g/mol 167 g/mol 0.140gm = ? = ô 17 6 go 50 acid is Theoretical- yield 0.170 gm of p-nitrobenzoic 2 melting point for p-nitrobenzoic acid Because melting of is large point of conjugation the p-nitrobenzoic acid is hidh It may so there 130 - 140°C expect to above 200°c melting point is in between. depending on atmosperic temperature

3 The colour of p-nitrotoluene is faint yellow or whitish yellow Because of Auxochromes. Initrogroup which increases the intensity. of absorption while colour of p-nitrobemoic acid is este to expected to to pale yellow because presence of carbonyl group which increases conjugation & also nitro group. increases conjugation, 애 NO2 NO2 faint yellow (some conjugation because of nitro group] pale yellow (more conjugation shift to Bathochromic shift