Featured contributor PhD Applied Physics; former research associate at a national metrology lab.

Dr. Helena Ortiz

Senior Reviewer, Science & Engineering

0 calculators 0 articles Member since Jun 2026

About

Helena is the senior technical reviewer for physics, chemistry, and unit-conversion calculators. She is the last pair of eyes on every formula — checking constants, units, and edge cases against primary sources and standards bodies.

She holds a PhD in Applied Physics and previously held a research post at a national metrology lab.

Areas of expertise

Physics Chemistry Unit conversion Measurement standards

Education & credentials

BSc Physics — Universidad Complutense de Madrid
PhD Applied Physics — Stanford University

Chemistry / Reactions

Osmotic Pressure Calculator

Compute the osmotic pressure Π of a dilute solution from the van 't Hoff factor i, the molarity M, and the temperature T...

basic

16,286 4.0 1 min

Chemistry

Gibbs Free Energy ΔG = ΔH − TΔS Calculator

Calculates Gibbs free energy change ΔG from enthalpy ΔH and entropy ΔS at any temperature to determine reaction spontane...

basic

15,692 4.1 1 min

Chemistry / Solutions

Mole Fraction from Mass Percent Calculator

Compute the mole fraction of solute A in a binary mixture from its mass percentage and the molar masses of solute and so...

basic

3,524 4.9 1 min

Physics / Mechanics

Telescope Magnification Calculator

Compute the magnification of a telescope from the focal lengths of the objective lens (or mirror) and the eyepiece, plus...

basic

20,164 3.9 1 min

Health

Macronutrient Split from Daily Calories Calculator

Converts calorie percentages for carbohydrates, protein, and fat into daily gram targets: carb 4 kcal/g, protein 4 kcal/...

basic

6,902 4.2 1 min

Chemistry

Joule-Thomson Temperature Drop Calculator

Compute the temperature change of a real gas during an isenthalpic (Joule-Thomson) throttling expansion: ΔT = μ_JT × ΔP,...

basic

7,237 4.2 1 min

Chemistry

Combustion Heat from Hess's Law Summation Calculator

Applies Hess's law to calculate the standard enthalpy of combustion: ΔH°_rxn = Σ(ν·ΔHf°)_products − Σ(ν·ΔHf°)_reactants...

basic

7,882 4.8 1 min

Chemistry

Percent Dissociation of Weak Acid Calculator

Compute the percent dissociation α of a weak acid from its Ka and initial molar concentration using the small-x approxim...

basic

16,350 4.3 1 min

Physics / Mechanics

Coefficient of Friction from Incline Angle Calculator

Compute the static coefficient of friction between a block and an incline by measuring the angle at which the block just...

basic

10,587 4.2 1 min

Physics / Mechanics

Wien's Displacement Calculator

Compute the peak wavelength of black-body emission from the absolute temperature using Wien's displacement law: λ_max =...

basic

24,139 4.5 1 min

Chemistry / Solutions

Dilution by Evaporation Calculator

Compute the final concentration of a non-volatile solute after a known fraction of solvent has evaporated, using mass co...

basic

9,874 4.9 1 min

Chemistry

Half-Life of a Second-Order Reaction Calculator

Compute the half-life of a second-order reaction A → products from the rate constant k (M⁻¹·s⁻¹) and the initial concent...

basic

11,232 4.5 1 min

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Reviewed by Dr. Helena Ortiz

These calculators were technically reviewed by Dr. Helena Ortiz for accuracy.

Chemistry / Reactions

Equilibrium Constant Calculator

Compute the equilibrium constant K_c from the concentrations of two products (with stoichiometric coefficients 1) divide...

basic

5,060 4.0 1 min

Conversions / Length

Length Converter

Convert between meters, kilometers, miles, feet, inches, and yards.

Featured basic

4,965 4.2 1 min

Chemistry / Solutions

Combined Gas Law Calculator

Find the missing pressure, volume, or temperature using the combined gas law for a fixed amount of gas.

basic

5,360 4.2 1 min

Physics / Electricity

Capacitance Calculator

Compute the capacitance of a parallel-plate capacitor from plate area, plate separation, and the dielectric constant.

basic

12,524 4.1 1 min

Chemistry / Solutions

pOH Calculator

Compute pOH from hydroxide ion concentration and the matching pH at 25 °C.

basic

18,221 4.2 1 min

Ecology / Carbon Footprint

Carbon Footprint Calculator

Estimate your annual personal CO₂e footprint from home energy, driving, flying, and diet — with adjustable emission fact...

Featured basic

15,826 4.9 1 min

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Dr. Helena Ortiz

Osmotic Pressure Calculator

Gibbs Free Energy ΔG = ΔH − TΔS Calculator

Mole Fraction from Mass Percent Calculator

Telescope Magnification Calculator

Macronutrient Split from Daily Calories Calculator

Joule-Thomson Temperature Drop Calculator

Combustion Heat from Hess's Law Summation Calculator

Percent Dissociation of Weak Acid Calculator

Coefficient of Friction from Incline Angle Calculator

Wien's Displacement Calculator

Dilution by Evaporation Calculator

Half-Life of a Second-Order Reaction Calculator

Reviewed by Dr. Helena Ortiz

Equilibrium Constant Calculator

Length Converter

Combined Gas Law Calculator

Capacitance Calculator

pOH Calculator

Carbon Footprint Calculator