# Percent Purity Calculator

Calculate percent purity of a chemical substance from mass measurements or titration data. Includes automatic purity grade classification and impurity.

## What this calculates

Calculate the percent purity of a substance using direct mass measurements or titration data. This calculator determines the percentage of pure substance in a sample, the mass of impurities, and classifies the purity grade.

## Inputs

- **Calculation Method** — options: Direct Mass Measurement, From Titration Data — Choose direct measurement if you know the pure mass, or titration if you have titration data.
- **Mass of Pure Substance** (g) — min 0 — Mass of the pure substance in the sample (for direct method).
- **Mass of Sample** (g) — min 0 — Total mass of the impure sample.
- **Volume of Titrant** (mL) — min 0 — Volume of titrant solution used to reach the endpoint.
- **Molarity of Titrant** (mol/L) — min 0 — Molar concentration of the titrant solution.
- **Molar Mass of Analyte** (g/mol) — min 0 — Molar mass of the substance being determined (for titration method).
- **Stoichiometric Ratio (analyte:titrant)** — min 0 — Mole ratio of analyte to titrant in the reaction (e.g., 1 for 1:1, 0.5 for 1:2).

## Outputs

- **Percent Purity** (%) — Percentage of pure substance in the sample.
- **Mass of Impurities** (g) — Mass of impurities in the sample.
- **Purity Grade** — formatted as text — Classification based on purity level (analytical, reagent, technical, etc.).
- **Calculation Details** — formatted as text — Summary of the calculation method used.

## Details

Percent purity is a measure of how much of a sample is composed of the desired substance versus impurities. It is calculated as % purity = (mass of pure substance / mass of sample) × 100. In analytical chemistry, purity is a critical quality metric for reagents, pharmaceuticals, and industrial chemicals.

When direct mass measurement is not possible, titration provides an indirect method to determine purity. A sample of known mass is dissolved and titrated with a standard solution of known concentration. The volume of titrant consumed at the equivalence point is used to calculate the moles of analyte, which is then converted to mass using the molar mass and stoichiometric ratio.

Chemical reagents are classified by purity grade. Analytical grade (≥99.5%) is required for quantitative analysis and research. Reagent grade (≥99.0%) is suitable for most laboratory purposes. Laboratory grade (≥95%) is acceptable for qualitative work, while technical grade (≥90%) is used for industrial processes where high purity is not critical.

## Frequently Asked Questions

**Q: How is percent purity calculated?**

A: Percent purity is calculated by dividing the mass of the pure substance by the total mass of the sample and multiplying by 100: % purity = (mass of pure substance / mass of sample) × 100. If you don't know the pure mass directly, titration or other analytical methods can determine it indirectly.

**Q: What is the stoichiometric ratio in titration purity calculations?**

A: The stoichiometric ratio is the mole ratio of the analyte to the titrant in the balanced chemical equation. For example, if NaOH (titrant) reacts with HCl (analyte) in a 1:1 ratio, the stoichiometric ratio is 1. If 2 moles of NaOH react with 1 mole of H₂SO₄, the ratio of analyte to titrant is 0.5.

**Q: What do the different purity grades mean?**

A: Analytical grade (≥99.5%) meets the specifications of the American Chemical Society and is suitable for precise quantitative analysis. Reagent grade (≥99.0%) is appropriate for most laboratory experiments. Laboratory grade (≥95%) is used for qualitative tests and teaching labs. Technical grade (≥90%) is used in manufacturing and industrial applications.

**Q: Can percent purity be greater than 100%?**

A: A measured purity above 100% indicates experimental error, such as incomplete drying of the sample (which adds extra mass), systematic errors in the titration, or contamination with a substance that also reacts with the titrant. Results should be rechecked if purity exceeds 100%.

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Source: https://vastcalc.com/calculators/chemistry/percent-purity
Category: Chemistry
Last updated: 2026-04-21