Percent Composition and Empirical Formulas

The topics found within this segment include converting moles to liters as well as calculating percent composition, empirical formulas, and molecular formulas.

The topics of this segment include converting moles to liters as well as calculating molecular and empirical formulas.

Premiere Date: July 11, 2016 | Runtime: 00:19:42

## Toolkit

Unit 6C Note Taking Guide & Segment Questions
Unit 6C Stoichiometry and Molar Volume Calculations Practice Problems
Unit 6C Percent Composition and Empirical Formulas Practice I
Unit 6C Percent Composition and Empirical Formulas Practice II
Unit 6C Percent Composition and Empirical Formulas Practice III
Unit 6C Percent Composition and Empirical Formulas Practice IV
Unit 6C Percent Composition and Empirical Formulas Practice V
Unit 6C Molecular Formulas Practice I
Unit 6C Molecular Formulas Practice II
Unit 6C Molecular Formulas Practice III
Unit 6C Reviewing Molar Mass and Molecular Formulas

## Crosscutting Concepts

Patterns

Observed patterns of forms and events guide organization and classification, and they prompt questions about relationships and the factors that influence them.

Scale, Proportion, and Quantity

In considering phenomena, it is critical to recognize what is relevant at different measures of size, time, and energy and to recognize how changes in scale, proportion, or quantity affect a system’s structure or performance.

## Science & Engineering Practices

Using Mathematics and Computational Thinking

Although there are differences in how mathematics and computational thinking are applied in science and in engineering, mathematics often brings these two fields together by enabling engineers to apply the mathematical form of scientific theories and by enabling scientists to use powerful information technologies designed by engineers. Both kinds of professionals can thereby accomplish investigations and analyses and build complex models, which might otherwise be out of the question. (NRC Framework, 2012, p. 65)

## Vocabulary

atomic mass unit - equals 1/12 the mass of a carbon atom.

Avagadro's number - the number of atoms in a mole, equal to 6.02x10^23 atoms.

conversion factor - a ratio expressed as a fraction that equals one.

dimensional analysis - the sequential application of conversion factors expressed as fractions and arranged so that any dimensional unit can be cancelled out until the desired set of dimensional units is obtained.

empirical formula - the simplest formula of a compound expressed as the smallest possible ratio of the elements.

equivalence statement - a statement that shows the quantities and units that are equal to each other.

excess reactant - the reactant in a chemical reaction that remains when a reaction stops once the limiting reactant is completely consumed.

limiting reactant - the reactant in a chemical reaction that limits the amount of product formed.

molar mass - the mass, in grams, of a mole of a substance.

molar volume - the volume of one mole of any gas at standard temperature and pressure.

mole - The SI unit that measures the amount of matter a substance has; one mole is equal to 6.022x10^23 representative particles, also known as Avagadro's number.

mole ratio - the ratio of moles of one substance to the moles of another substance in a balanced equation.

molecular formula - a formula which states the exact number and type of each atom present in a molecule of a substance.

percent composition - the percentage by mass of each element in a compound.

percent yield - the ratio of the actual yield to the theoretical yield of a material.

stoichiometry - the calculation of the quantities of reactants and products involved in a chemical reaction.

theoretical yield - the amount of product formed from the complete conversion of a limiting reactant in a chemical reaction.

## Georgia Standards of Excellence

SC3.bPlan and carry out investigations to determine that a new chemical has formed by identifying indicators of a chemical reaction (specifically precipitate formation, gas evolution, color change, water production, and changes in energy to the system should be investigated).

SC3.cUse mathematics and computational thinking to apply concepts of the mole and Avogadro’s number to conceptualize and calculate:

• percent composition

• empirical/molecular formulas

• mass, moles, and molecules relationships

• molar volumes of gases

(Clarification statement for elements c and d: Emphasis is on use of mole ratios to compare quantities of reactants or products and on assessing students’ use of mathematical thinking and is not on memorization and rote application of problem- solving techniques.)

SC3.dUse mathematics and computational thinking to identify and solve different types of reaction stoichiometry problems (i.e., mass to moles, mass to mass, moles to moles, and percent yield) using significant figures. (Clarification statement for elements c and d: Emphasis is on use of mole ratios to compare quantities of reactants or products and on assessing students’ use of mathematical thinking and is not on memorization and rote application of problem- solving techniques.)

## Request Teacher Toolkit

The Chemistry Matters teacher toolkit provides instructions and answer keys for labs, experiments, and assignments for all 12 units of study. GPB offers the teacher toolkit at no cost to Georgia educators. Complete and submit this form to request the teacher toolkit. You only need to submit this form one time to get materials for all 12 units of study.