Reactants calculating mass

Step 1 Convert the mass of each reactant into moles, if necessary, by using the molar masses of the substances. Step 2 Select one of the products. For each reactant, calculate how many moles of the product it can form. Step 3 The reactant that can produce the least amount of product is the limiting reactant. 

The fission of one mole of uranium-235 produces more energy than the fusion of one mole of deuterium with one mole of tritium. What if you compare the energy that is produced in terms of mass of reactants Calculate a ratio to compare the energy that is produced from fusion and fission, per gram of fuel. What practical consequences arise from your result ... 

You will notice that the total mass of reactants is equal to the total mass of product. This is true for any chemical reaction and it is known as the Law of conservation of mass. This law was understood by the Greeks but was first clearly formulated by Antoine Lavoisier in 1774. Chemists can use this idea to calculate masses of products formed and reactants used in chemical processes before they are carried out. 

There is another method that some of our students find works well They calculate the mass of product expected based on each reactant. The limiting reactant is that reactant that gives the smallest quantity of product. For example, refer to the SiCL reaction with Mg on page 158. To confirm that SiCL is the limiting reactant, calculate the quantity of elemental silicon that can be formed starting with (a) 1.32 mol of SiCL and unlimited magnesium or (b) with 9.26 mol of Mg and unlimited SiCL. 

Given the masses of two or more reactants, calculate the maximum mass of product that could form from the reaction between them. 

Reaction path models calculate a sequence of equilibrium states involving incremental or step-wise mass transfer between the phases within a system, or incremental addition or subtraction of a reactant from the system, possibly accompanied by an increase or decrease of temperature and pressure (Helgeson, 1968, 1969). The calculated mass transfer is based on the principles of mass balance and thermodynamic equilibrium. Unlike speciation-solubility calculations, which deal with the equilibrium state of a system, the reaction path model simulates processes, in which the masses of the phases play a role. 

It should be stressed that in the case of exoergic proton transfer reactions involving small reactant neutrals (masses up to 100 Dalton), the measured values of k invariably agree with k to within a few percent. When rate constants are needed for measuring densities of VOCs using PTR-MS, it is recommended that calculated values of k be used unless very reliable experimental data are available. 

Analytical chemistry deals with measurements of solids and solution concentrations of them, from which we calculate masses. Thus, we prepare solutions of known concentrations that can be used to calibrate instruments or to titrate sample solutions. We calculate the mass of analyte in a solution from its concentration and the volume. We calculate the mass of product expected from the mass of reactants. All of these calculations require a knowledge of stoichiometry, that is, the ratios in which chemicals react, from which we apply appropriate conversion factors to arrive at the desired calculated results. 

Chemical equations are an indispensable way of representing reactions. They are routinely used to calculate masses of reactants and products. In the case of the examples used above for the Law of Multiple Proportions, the equations are ... 

To calculate masses from fhe moles of reactants needed or products formed, we can use the molar masses of substances for finding the masses (g) needed or formed. 

Solution Stoichiometry Calculating Mass of Reactants and Products... 

Solution Stoichiometry Determining Limiting Reactants and Calculating Mass of Products... 

Calculating Masses of Reactants and Products in Chemical Reactions... 

Calculating the limiting reactant The masses of both reactants are given. First, determine which one is the limiting reactant, because the reaction stops producing product when the limiting reactant is used up. 

We have already discussed how to calculate masses of solids or volumes of gases, for the reactants or products in balanced equations. What if solutions are involved in the reaction An aqueous solution may be concentrated or dilute. That is, it may contain a large or small amount of solid dissolved in a given amount of water as shown in Fig. 9.1. 

The formation of gas bubbles bypasses reactant away from contact with the catalyst phase, although this effect is alleviated to some extent by exchange of reactant via mass transfer as well as bulk flow across the bubble surface. The bubbles coalesce to large sizes in their ascent through the bed. Our interest is in calculating the conversion in the reactor, which is assumed to occur under isothermal conditions. The following considerations are extremely important in the formulation of the population balance model. 

In Chapter 6, we learned how a chemical formula contains conversion factors for converting between moles of a compound and moles of its constituent elements. In this chapter, we have seen how a chemical equation contains conversion factors between moles of reactants and moles of products. However, we are often interested in relationships between mass of reactants and mass of products. For example, we might want to know the mass of carbon dioxide emitted by an automobile per kilogram of gasoline used. Or we might want to know tire mass of each reactant required to obtain a certain mass of a product in a S5mthesis reaction. These calculations are similar to calculations covered in Section 6.5, where we converted between mass of a compound and mass of a constituent element. The general outline for these types of calculations is ... 

Find the limiting reactant by calculating how much product can be made from each reactant. The reactant that makes the least amount of product is the limiting reactant. The mass of ammonia formed by the limiting reactant is the maximum amount of ammonia that can be synthesized. 

A reaction vessel initially contains 10.0 g of each of the reactants. Calculate the masses of Ti02, C, Ti, and CO that will be in the reaction vessel once the reactants have reacted as much as possible. (Assume 100% yield.)... 

Calculating Quantities in a Limiting-Reactant Problem Mass to Mass... 

EXAMPLE 3.16 Calculating with a Limiting Reactant (Involving Masses)... 

Calculating Mass of Product from a Limiting Reactant... 

SOLVE Beginning with the given mass of each reactant, calculate the amount of product that can be made in moles. Convert the amount of product made by the limiting reactant to grams—this is the theoretical yield. 

Cumene is produced from the reaction of benzene and propylene at 25°C and 1 atm. The inlet mass flow rate of benzene is 1000 kg/h and that of propylene is 180 kg/h. Assume 45% completion of the limiting reactant. Calculate molar flow rates of the product stream. 

Observed and Calculated Mass Yields of Alucone Polymers, Indicating Reactants and Conditions of Isolation... 

These conversion factors are used in Example 25-5, together with the principle that the total mass-energy of the products of a nuclear reaction is equal to the total mass-energy of the reactants. The masses required in calculations based on nuclear reactions are nuclear masses. The relationship of a nuclear mass to a nuclidic (atomic) mass is... 

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