Mass Calculations for Reactions

When we have the balanced chemical equation for a reaction, we can use the mass of one of the substances (A) in the reaction to calculate the mass of another substance (B) in the reaction. However, the calculations require us to convert the mass of A to moles of A using the molar mass factor for A. Then we use the mole-mole factor that links substance A to substance B, which we obtain from the coefficients in the balanced equation. This mole-mole factor (B/A) will convert the moles of A to moles of B. Then the molar mass factor of B is used to calculate the grams of substance B. 

A mixture of acetylene and oxygen undergoes combustion during the welding of metals. 

When acetylene, C2H2, bums in oxygen, high temperatures are produced that are used for welding metals. 

How many grams of CO2 are produced when 54.6 g of C2H2 is burned  

STEP D State the given and needed quantities (grams). 

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Mass Calculations for Reactions, prepare students for the quantitative relationships of reactants and products in reactions. The chapter concludes with Section 7.8, Energy in Chemical Reactions, which discusses activation energy and energy changes in exothermic and endothermic reactions. 

Sample Calculations walk students through the most challenging chemistry problems and provide a fresh perspective on how to approach individual problems and reach their solutions. Topics include Using Conversion Factors, Mass Calculations for Reactions, and Concentration of Solutions. 

Carry out mole-to-mole, mass-to-mole, and mass-to-mass calculations for any two species involved in a chemical reaction, Example L.l. 

We know the amounts of pure substances by converting their masses into number of moles. But for dissolved substances, we need the concentration— the number of moles per volume of solution—to find the volume that contains a given number of moles. In this section, we first discuss molarity, the most common way to express concentration (Chapter 13 covers others). Then, we see how to dilute a concentrated solution and how to use stoichiometric calculations for reactions in solution. 

In Chapter 13, you learned how to use moles and molar mass along with a balanced chemical equation to calculate the masses of reactants and products in a chemical reaction. Now that you know how to relate volumes, masses, and moles for a gas, you can do stoichiometric calculations for reactions involving gases. 

By applying the conservation equations of mass and energy and by neglecting the small pressure changes across the flame, the thickness of the preheating and reaction 2ones can be calculated for a one-dimensional flame (1). 

By analogy with similar materials in which free elecU ons and electron holes are formed, NiO is called a p-type compound having vacant site Schottky defects, and ZnO is an n-type compound having interstitial Frenkel defects. The concentrations of these defects and their relation to the oxygen pressure in the suiTounding atmosphere can be calculated, for a dilute solution of defects by the application of a mass action equation. The two reactions shown above are represented by the equations... 

The mass transfer coefficient is calculated for a given diffusivity coefficient and reaction rate constant at the equilibrium concentration of oxygen. When oxygen is continuously transported and removed from the liquid phase we may write ... 

Changes in free energy and the equilibrium constants for Reactions 1, 2, 3, and 4 are quite sensitive to temperature (Figures 2 and 3). These equilibrium constants were used to calculate the composition of the exit gas from the methanator by solving the coupled equilibrium relationships of Reactions 1 and 2 and mass conservation relationships by a Newton-Raphson technique it was assumed that carbon was not formed. Features of the computer program used were as follows (a) any pressure and temperature may be specified (b) an inert gas may be present (c) after... 

The kinetic equilibrium constant is estimated from the thermodynamic equilibrium constant using Equation (7.36). The reaction rate is calculated and compositions are marched ahead by one time step. The energy balance is then used to march enthalpy ahead by one step. The energy balance in Chapter 5 used a mass basis for heat capacities and enthalpies. A molar basis is more suitable for the current problem. The molar counterpart of Equation (5.18) is... 

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