Chapter 4 Chemical Quantities and Aqueous Reactions Sections

Chapter 4: Chemical Quantities and Aqueous Reactions Sections: 4.2-4.9 Important Questions and Concepts: How do we use stoichiometry to convert between amounts of different substances (reactants or products) in a reaction? . What is a limiting reagent? How do we determine what the limiting reagent in a reaction is? What is the theoretical yield? Do we ever achieve the theoretical yield? What is the actual yield? How is the percent yield calculated? What are the components of a solution? What is the molarity of a solution? How do we make solutions? . What is dilution? What equation can we use for dilution problems? . Why do solids dissolve in water? What happens to ionic compounds when they dissolve? What is an electrolyte? What makes an electrolyte strong or weak? How do we predict whether an ionic compound is soluble or insoluble? . What is a precipitation reaction? How do we determine if a precipitate is formed when mixing two solutions? . What is an acid? What is a base? What are the products of a neutral. . What is a titration? What equation can we use for titration problems? . What is a gas evolving reaction? ization reaction? How do we determine when we reach the equivalence point? What is an oxidation state/number? How do we determine the oxida- tion number of the atoms in a compound? . What is oxidation? What is reduction? How do we determine what is reduced and what is oxidized in an oxidation reduction reaction? Additional Practice Problems:

Solution

Ans:-

# The word stoichiometry means , (stoichio- elemental and metry- measurement) elemental measurement . In order to solve the problems related with products yields (i.e how many moles or grams of products are formed from reactants) a chemical equation should be balanced.

# with the help of stoichiometric coefficient ( is the number appearing before the symbol for each compound after balancing equation) , we can easily determine the Theoretical yields of products species.

# limiting reagent or reactant is the reactant which is present in lesser amount or which is completely consumed in a chemical reaction .

We can simply determine the limiting reagent by using the formula , given number of moles of substance divided by stoichiometric coefficient . If this no.( i.e given no. Of moles / stoichiometric coefficient) is less for one reactant as compared to other ,then that raectant ( former) is known as limiting reactant.

# limiting reactant limit the product that is formed, means limiting reagent gives the smallest yields of products, and this smallest yields of products, which is obtained from limiting reactant is known as Theoretical yield.

# The amount actually produced of a products during experiment is called actual yield.

# The ratio of actual yield to the theoretical yield multiply by 100 is known as percent yield.

Percent yield = actual yield ×100 / theoretical yield

# a binary solution have two components i.e one is solute( which is present in lesser amount) and other is solvent ( present in excess amount in sol.) .

because , solvent is the first component of the solution ,therefore solvent generally denoted with numerically 1 and alphabetically A , similarly solute is the second component of the solution , therefore denoted by 2 and B.

# Molarity is the number of moles of solute present in 1 litre of a solution.

i.e Molarity = no.of moles of solute / Vol. of sol. in Litre

# The pocess of adding water in the solution is known as dilution. During this process no. of moles of solute before dilution and no. of moles after dilution remains same . Therefore equation of dilution is:

No.of moles before dilution = no.of moles after dilution

i.e M1V1= M2V2

M1= molarity of solution before dilution , V1= volume of sol. before

dilution

M2= molarity of sol. after dilution, V2= Volume of sol. after dilution.