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.

Convert numbers to scientific notation by placing the decimal between 1 and 10 and using ten to the correct power, for both large and small values.

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.

Learn to balance chemical equations as the second step in a four-step stoichiometry process, using a preliminary equation and atom counts to ensure conservation of mass across reactants and products.

Follow a four-step method to balance stoichiometric equations, focusing on steps 3 and 4: select applicable elements, then adjust coefficients to balance remaining substances, using color-coding to visualize atoms.

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.

Balance the most complicated combustion example by using element counting, choosing a single-occurrence element, applying fractional coefficients, and converting to integers to complete the stoichiometry.

Explore stoichiometry by using simple mass ratios rather than complex molecules, showing how grams map to items and how mass and item counts differ in predicting products.

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.

The omelette metaphor extends stoichiometry to non-1 gram items, using eggs at 23 g and bacon at 19 g to teach mass-based and item-based ratios and limiting reagent.

Using the omelet analogy, the lecture covers theoretical yield, actual yield, and percent yield, showing mass and item basis calculations (42 g per omelet).

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 how mass units can mislead in stoichiometry by converting to an item-to-item basis with dimensional analysis. Identify the limiting reactant and calculate final mass as three grams, not five.

Apply stoichiometry concepts by identifying limiting and excess reagents, converting from mass basis to item basis, and avoiding the mass-to-mass trap to predict product mass.

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.

Use the omelette metaphor to determine yields by converting masses to item bases, comparing mass versus item basis methods, identifying the limiting reagent, and computing the theoretical yield.

Explore item-to-item versus pack-based stoichiometry to predict yields and identify the limiting reagent. Use mass conversions to handle large quantities more easily.

Learn how packs replace items to simplify mass calculations, using a 12-item per pack convention to convert between item counts and total grams in eggs, bacon, and omelets.

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.

Explore molarity as a concentration unit, distinguishing moles of solute from the volume of the solution, and avoid confusing solvent volume with solution volume through a Zombie Steve example.

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 micro molar to milligram per liter through dimensional analysis and molecular weight, using Fred's transfiguration potion example to illustrate unit conversions from micro moles to milligrams per liter.

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 spot pitfalls in mass-to-mole conversions, such as misinterpreting the 62.5 g/mol weight and forgetting mg to g conversion, ensuring correct grams per mole usage.

Learn stoichiometry and lab calculations to prepare a 0.025 molar solution by converting moles to grams using molecular weight, then dissolve powder and dilute to 500 ml.

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.

After a lab explosion, this lecture reworks a stoichiometry problem by converting the remaining 0.400 g Zebedee to moles using 74.1 g/mol and targeting 0.0225 M solution.

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.

Apply concentration by removing solvent to raise molarity using the M1V1 = M2V2 approach. Begin with 240 ml at 0.0225 M and concentrate to about 24 ml to reach 0.25 M.

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.

learn how transmittance and absorbance relate in Beer’s law using a spectrophotometer, including how to calculate absorbance from transmittance and interpret data reliability.

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 sulfuric acid molarity by titrating with a known 0.001 M sodium hydroxide using a burette and phenolphthalein indicator to reach the endpoint. Apply the 2:1 stoichiometry to compute molarity.

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.

Explains how to derive pKa from titration data using the Henderson-Hasselbalch framework, emphasizing half-equivalence and equivalence points, Ka, conjugate base, and visual data interpretation with Excel.

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.

Analyze triprotic titration data by graphing pH versus sodium hydroxide volume, adding axis labels, and identifying inflection points and half-equivalence volumes using slope calculations and a secondary axis.