Ammonia is a principal nitrogen fertilizer. It is prepared by the reaction between hydrogen and nitrogen. 3H2(g)+N2(g)---->2NH3(g) In a particular reaction, 3.00 moles of NH3 were produced. How many moles oh H2 and how moles of N2 were reacted tp produce this amount NH3?   _____mol H2 _____mol N2   ______mol H2 ______mol N2

4-103 Caffeine, a central nervous system stimulant, has the molecular formula C8H10N402. (a) How many moles of caffeine are present in 6.19 1025 molecules of caffeine? (b) Imagine you dissolve caffeine in water to a volume of 100.0 mL, which is known to have a density of 1.23 g/mL. How many molecules of caffeine are present in this volume? (c) How many nitrogen atoms are present in 3.5 mg of caffeine? (d) Complete the skeletal structure of caffeine, where all the bonded atoms are shown but double bonds, triple bonds, and/or lone pairs are missing. (e) Identify the various types of geometries present in each central atom of caffeine using VSEPR theory. (f) Determine the various relative bond angles associated with each central atom of caffeine using VSEPR theory (g) What is the most polar bond in caffeine? (h) Would you predict caffeine to be polar or nonpolar? (j) Consider the combustion of caffeine, which results in formation of NO2(g) as well as other expected products. Write a balanced chemical equation for this reaction. (j) The heat of combustion for caffeine is 2211 kcall/mol. How much heat will be given off if 0.81 g of caffeine is burned completely? (k) Calculate the weight of H2O(g) that can be prepared from 8.00 g of caffeine mixed with 20.3 g of oxygen gas.

The pictures below show a molecular-scale view of a chemical reaction between H2 and CO to produce methanol, CH3OH The box on the left represents the reactants at the instant of mixing, and the box on the right shows what is left once the reaction has gone to completion. D Was there a limiting reactant in this reaction? If so, what was it? Write a balanced chemical equation for this reaction. As usual, your equation should use the smallest possible whole number coefficients for all substances.

3.15 Ethanol, C2H5OH is found in gasoline blends used in many parts of North America. Write a balanced chemi- cal equation for the combustion of C2H5OH to form CO2 and HA.

Polychlorinated biphenyls (PCBs) have been used extensively as dielectric materials in electrical transformers. Because PCBs have been shown to be potentially harmful, analysis for their presence in the environment has become very important. PCBs are manufactured according to the following generic reaction: C12H10+nCl2C12H10nCln.+nHCl This reaction results in a mixture of PCB products. The mixture is analyzed by decomposing the PCBs and then precipitating the resulting Cl asAgCl. a. Develop a general equation that relates the average value of n to the mass of a given mixture of PCBs and the mass of AgCl produced. b. A 0.1947-g sample of a commercial PCB yielded 0.4791 g of AgCl. What is the average value of n for this sample?

A weighed sample of iron (Fe) is added to liquid bromine (Br2) and allowed to react completely. The reaction produces a single product, which can be isolated and weighed. The experiment was repeated a number of times with different masses of iron but with the same mass of bromine (see graph below). (a) What mass of Br2 is used when the reaction consumes 2.0 g of Fe? (b) What is the mole ratio of Br2 to Fe in the reaction? (c) What is the empirical formula of the product? (d) Write the balanced chemical equation tor the reaction of iron and bromine. (e) What is the name of the reaction product? (f) Which statement or statements best describe the experiments summarized by the graph? (i) When 1.00 g of Fe is added to the Br2, Fe is the limiting reagent. (ii) When 3.50 g of Fe is added to the Br2, there is an excess of Br2. (iii) When 2.50 g of Fe is added to the Br2, both reactanu are used up compietely. (iv) When 2.00 g of Fe is added to the Br2, 10.8 g of product is formed. The percent yield must therefore be 20.0%.

Carbon dioxide from the atmosphere weathers, or dissolves, limestone (CaCO3) by the reaction CaCO3(s)+CO2(g)+H2O(l)Ca2(aq)+2HCO3(aq) Obtain H for this reaction. See Table 6.2 for the data.

Aluminum Chloride and Sodium Metal react, forming Aluminum and Sodium Chloride:   AlCl3 + 3 Na →  Al + 3 NaCl    This can be read as 1 mole of AlCl3 reacts with 3 moles of Na to form 1 mole of Al + 3 moles of NaCl.    If you had 7 moles of AlCl3, how many moles of Na would you need to react?          _______ mol Na    If you wanted to make 2 moles of Aluminum, how many moles of AlCl3 and Na would you need? _______ mol AlCl3  _______ mol Na

Fe2O3 + 3 C →→ 2 Fe  + 3 CO How many moles of Fe2O3 are required to react with 9.1 mol of C?  _______ mol Fe2O3

For the following reaction, 102 grams of aluminum oxide are allowed to react with 491 grams of sulfuric acid. Al2O3(s) + 3H2SO4(aq) ------>  Al2(SO4)3(aq) + 3H2O(l)   What is the FORMULA for the limitin reagent? _______What is the maximum amount of aluminum sulfate that can be formed?  _______gramsWhat amount of the excess reagent remains after the reaction is complete?  ______grams