The Concept of Limiting Reactant

Earlier in this chapter, we discussed making sandwiches. Recall that the sandwich-making process could be described as follows  

2 pieces bread -i- 3 slices meat -i- 1 slice cheese sandwich 

In our earlier discussion, we always purchased the ingredients in the correct ratios so that we used all of the components, with nothing left over. 

Now assume that you came to work one day and found the following quantities of ingredients  

20 slices of bread 24 slices of meat 12 slices of cheese 

OBJECTIVE To understand what is meant by the term limiting reactant.  

2 pieces bread + 3 slices meat + 1 slice cheese — 1 sandwich 

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In Section F, we saw that one technique used in modern chemical laboratories to determine the empirical formulas of organic compounds is combustion analysis. We are now in a position to understand the basis of the technique, because it makes use of the concept of limiting reactant. 

Before analyzing the several forms of the material balances, the concept of limiting reactant will be presented fust as the sizing of the reactor is normally based on this reactant. 

In Section F, we remarked that one technique used in modern chemical laboratories or the agencies that carry out contract work on behalf of other chemists is combustion analysis. This technique—which has been used since the earliest days of chemistry—is used to establish the empirical formulas of organic compounds and, in combination with mass spectrometry, their molecular formulas. It is used both for newly synthesized compounds and to identify active compounds in natural products. We are now in a position to understand the basis of the technique, for it makes use of the concept of limiting reactant. 

Use the concept of limiting reactants to explain why fuel-air ratios affect engine performance. 

Information Given by Chemical Equations Mole-Mole Relationships Mass Calculations The Concept of Limiting Reactants... 

Section 9.4 The Concept of Limiting Reactants We have added a new section that helps students better understand the concept of a limiting reactant. Familiar examples such as making sandwiches and lemonade are used, as well as molecular-level illustrations of chemistry reactions. Students will learn how to think about limiting reactants before being asked to make mass-mass calculations to determine which reaaant is limiting for a given reaction. 

The concept of limiting reactants has some important implications for engineering applications where chemical reactions are involved. We ve already... 

The Concept of Limiting Reactants 219 Consider the following container of N2( ) and HzCg) ... 

Refer to Figure 5.2 and follow the instmctions. Then explain how the concept of limiting reactant is used to extinguish a fire. 

Molar Mass Learning to Solve Problems 3.8 Compound Chemical Equations Chemical Reactions 3.11 Products The Concept of Limiting Reactant... 

Since air is 20.8% oxygen (by volume) the stoichiometric (4 1) concentration of gaseous acetone will be 5.2%. However, the concept of limiting reactant suggests that any combination of acetone and oxygen would burn as long as both are present. So, the acetone should burn in air in some closed container, assuming excess O2 in air, until... 

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