Chemistry for Beginners - Stoichiometry and Lab Calculations

Explore why scientific notation matters in the chemistry lab and master multiplying and dividing numbers written as ten to the exponent, including positive and negative exponents.

Multiply numbers written in scientific notation by multiplying mantissas and adding exponents, then apply significant figures to keep precision.

Learn to divide in scientific notation by subtracting exponents, shown with examples like 2×10^2 ÷ 1×10^1, and adjust results when exponents become negative.

Balance chemical equations by applying a stepwise method: compare carbon, oxygen, and hydrogen counts, adjust coefficients in reactants to satisfy product side, and use visual inspection when helpful.

Balance sulfur and oxygen reactions by using fractional coefficients to simplify balancing, then convert to whole numbers by multiplying all coefficients by the denominator.

Balance a combustion problem by reacting SH with oxygen to yield water and CO2, adjust hydrogen by changing the coefficient, then balance oxygen to finalize the equation.

Explore how the block metaphor shows stoichiometry with excess reagents, using dimensional analysis to switch from mass to an item-based perspective.

Explore how an omelet with one egg and one bacon illustrates stoichiometry, showing how the egg acts as the limiting reagent and defines the theoretical yield.

Explore more complex stoichiometry by predicting products from blue and red piece models, identify limiting reagents and excess, then transition from item-to-item to mass-to-mass calculations.

Explore stoichiometry using an omelet metaphor, comparing one-to-one and two-to-one ratios of eggs and bacon. Learn to calculate item-to-mass ratios, weigh outcomes, and perform lab-ready calculations before mass-to-mass considerations.

Explore how using packs instead of grams simplifies stoichiometry calculations, identify limiting reagents, and apply dimensional analysis as a stepping stone to understanding the mole.

Transform your thinking from individual items to moles as a counting unit, using ibuprofen to show that one mole equals 206 grams, enabling stoichiometry calculations of theoretical and actual yield.

Learn to use moles in calculations by determining molecular weight of salicylic acid, either by summing atomic weights or by lookup, in a stoichiometry context.

Explore stoichiometry by converting masses to moles, identify the limiting reagent using mole ratios, and compute theoretical yield in grams from millimoles with salicylic acid and acetic anhydride.

Compute percent yield from actual and theoretical yields, using mass or mole bases, apply rounding to significant figures, and convert to millimoles, as shown with aspirin.

Explain why molarity is not a physical constant and show four lab methods to adjust it: dilute or concentrate by solvent, add solute, and use chromatography.

Convert milligrams per liter to micro molar using the TP powder's molecular weight and gram-to-milligram conversions, linking milligrams per liter to micro molarity through the mole concept.

Learn to prepare a desired molarity by measuring the solid first, starting below the target volume, then dissolving and adding solvent to reach 500 milliliters.

Apply the M1V1 = M2V2 dilution equation to adjust solution concentration by adding solvent. Solve for V1 to reach a chosen final volume and target concentration, with real-world lab calculations.

Concentrate a solution by adding solute, accounting for volume changes, and use molarity calculations to determine grams to add from molar mass.

Learn how a spectrophotometer measures light spectrum to verify solution concentration with numerical data, illustrating how concentration affects transmitted light. Note chromatography as a potential dilution method.

Apply Beer's law to determine concentration from absorbents measured with a spectrophotometer. Use molar absorptivity and path length, with absorbents as a unitless value between zero and one.

Create a calibration curve from known concentrations, applying Beer's law with extinction coefficients to determine the unknown concentration for stoichiometry and lab calculations.

Use excel to enter absorbance and x-axis data, apply scientific notation, and create an xy scatter chart, then format axes and zoom to reveal a straight-line relationship for unknown concentrations.

Connect data points in Excel with a trend line, display the r squared value and equation, and use Beer's law with calibration curves to determine unknown concentrations.

Use acid-base titration to determine concentration by measuring volumes, in addition to spectroscopy. Balance neutralization equations and relate known and unknown solutions, like sulfuric acid and sodium hydroxide.

Determine pKa from titration data by locating the equivalence point and the half equivalence point on a pH versus volume graph, comparing acid strengths using common lab setup.

Learn to derive pKa from titration data in Excel by graphing, computing slope, and locating the equivalence and half-equivalence points.

Explore titration of citric acid in lemon juice, reveal its triprotic acidity, and apply stoichiometry with sodium hydroxide until phenolphthalein turns pink.

Learn how to calculate moles and molarity in a triprotic titration by converting volumes, applying mole ratios, and converting moles to grams for citric acid in lemon juice.