The oxidation number of chromium (Cr) in potassium dichromate (K_2 Cr_2 O_7) is.

Question

The oxidation number of chromium (Cr) in potassium dichromate (K_2 Cr_2 O_7) is. Ethylene glycol in aqueous solution is used as anti-freeze in car radiators. The weight of ethylene glycol(CH_2 OH)_2 required to make 17 L of 5 M ethylene glycol is: 0.31 kg 1.06 kg 2.64 kg 5.28 kg 10.56 kg None of above; the correct weight is kg When 50 mL of 1.0 M AgN0_3 are mixed with 50 mL of 1.0 M NaCl in a coffee-cup calorimeter, the temperature of the resulting solution increases from 23.00 degree C to 30.87 degree C. Assume that the calorimeter loses only a negligible quantity of heat, that the total volume of the solution is 100 mL, that its density is 1.00 g middot mL^-1 and that its specific heat is 4.184 J middot g^-1 K^-1. The enthalpy of reaction (delta H) of the reaction Ag^+(aq) + Cl^-(aq) rightarrow AgCl(s) is: -65.9 kJ -32.9 kJ -15.7 kJ -6.6 kJ -3.3 kJ None of the above; the correct heat of reaction is J The following enthalpies of reaction are given for the combustion of ethane (C_2 H_6), ethylene (C_2 H_4)

Explanation / Answer

10. Oxidation number of Cr = +6

11) Moles of ethylene glycol = 5M *17L

= 85 mol

Mass of ethylene glycol = moles * molar mass

= 85 mol * 62 g/mol

= 5270 g

= 5.27 kg

Answer : d) 5.28 kg

12) q (solution) = 100g *4.184J/g deg C * (30.87- 23)deg C

= 3293J

= 3.30 kJ

Heat of reaction = -3.30kJ

Answer : e) -3.3 kJ

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