Answer to Question #210894 in General Chemistry for Zack

Question

An ammonia gas-sensing electrode gave the following calibration points when all solutions contained 1 M NaOH. NH3 (M) E (mV) NH3 (M) E (mV) 1.00 105 268.0 5.00 104 368.0 5.00 105 310.0 1.00 103 386.4 1.00 104 326.8 5.00 103 427.6 A dry food sample weighing 312.4 mg was digested by the Kjeldahl procedure (Section 10-8) to convert all nitrogen into NH4 . The digestion solution was diluted to 1.00 L, and 20.0 mL were transferred KPot Na,H 36 to a 100-mL volumetric flask. The 20.0-mL aliquot was treated with 10.0 mL of 10.0 M NaOH plus enough NaI to complex the Hg catalyst from the digestion and diluted to 100.0 mL. When measured with the ammonia electrode, this solution gave a reading of 339.3 mV. Calculate the wt% nitrogen in the food sample. 

Answer 1

Stoichiometry of Chemical Reactions A. Chemical Equations 1. Chemical equations use chemical symbols to denote what occurs in a chemical reaction. 2. Reactants are on the left side 3. Products are on the right side 4. Labels used = gas (g), liquid (l), solid (s), and aqueous (aq) a. Water is not aqueous, it is a liquid B. Balancing Equations 1. Must be balanced, so that the law of conservation of mass is obeyed 2. Balancing is achieved by writing stoichiometric coefficients to the left of the chemical formulas a. Not Balanced H2 (g) + O2 (g)  H2O (l) b. Balanced 2H2 (g)