An alkaline battery produces energy according to the reaction below. Determine the limiting reactant if 25.0 g Zn and 62.5 g MnO2 are used. Determine the
theoretical yield in grams of Zn(OH)2. If 32.6 g of Zn(OH), are actually produced,
what is the percent yield?
Zn(s) + 2 MnO2(s) + H2O(l) → Zn(OH)2(s) + Mn, O3(s)

The enthalpy of formation of water is -285.8 kj/mol. what can be inferred from this statement?

A3.37-mg sample of protein was chemically digested to convert its nitrogen into ammonia and then diluted to 100.0 ml. then 10.0 ml of this solution was placed in a 50-ml volumetric flask and treated with 5 ml of phenol solution plus 2 ml of sodium hypochlorite solution. the sample was diluted to 50.0 ml, and the absorbance at 625 nm was measured in a 1.00-cm cuvette and found to be 0.486. for reference, a standard solution was prepared from 10.0 mg of nh4cl (molar mass = 53.49 grams/mole) dissolved in 1.00 l of water. then 10.0 ml of this standard was placed in a 50-ml volumetric flask, treated in the same manner as the unknown, and the absorbance found to be 0.323. finally, a reagent blank was prepared using distilled water in place of unknown, it was treated in the same manner as the unknown, and the absorbance found to be 0.076. calculate the weight percent of nitrogen in the protein.

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?