First-year undergraduate

General chemistry practical

The calculations a first-year practical actually asks for, in the order most courses meet them: weigh-outs, dilutions, percent solutions, stoichiometry, then acids, bases, and buffers.

12 calculators, in the order the course uses them. Every one shows its working, flags the hazards, and keeps working offline once the page has loaded. Free, and no account is needed.

Start with Molar mass, grams and moles All topics and reference tables

In course order

What this practical calculates

1. Molar mass, grams and moles

Type an element or formula (Sb, NaCl, C6H12O6) and convert grams to moles. Molar mass is computed from cited atomic weights.

How it works · Practice problems · n = m / MW

2. Molarity, mass and volume conversion

Convert between molarity, mass, volume, and moles for a reagent, in any direction.

How it works · Practice problems · n = m / MW ; c = n / V

3. Hydrate mass adjuster

Protocol assumes one hydrate, you have another? Get the corrected mass.

How it works · Practice problems · m_have = m_protocol · MW_have / MW_protocol

4. Simple dilution

C₁V₁ = C₂V₂, exactly how much stock and diluent to mix.

How it works · Practice problems · C₁ · V₁ = C₂ · V₂

5. Serial dilution

A fold-dilution series, tube by tube.

How it works · Practice problems · Cₙ = C₀ / fⁿ

6. % concentration

Convert %w/v, %w/w, %v/v ⇄ g/L and molarity.

How it works · Practice problems · %w/v · 10 = g/L

7. Reaction balancer

Exact integer coefficients by rational null-space. Unbalanceable input is flagged, never fudged.

How it works · element-conservation null space

8. Limiting reagent and yield

Which reagent runs out, the theoretical yield, and what is left over.

How it works · limiting = min(n / coeff) ; yield = limiting · coeff_p · MW_p

9. Acid / base dilution

Turn a bottle label (%w/w + density) into a safe dilution protocol.

How it works · Practice problems · M = 10·%·ρ / MW ; C₁V₁ = C₂V₂

10. Buffer / pH

Henderson-Hasselbalch, the acid/base split for a target pH.

How it works · Practice problems · pH = pKa + log₁₀([A⁻]/[HA])

11. Molarity to normality

N = M × n, with the equivalence factor you confirm for the reaction.

How it works · Practice problems · N = M · n

12. RPM ⇄ RCF

Convert centrifuge speed to g-force using the rotor radius.

How it works · Practice problems · RCF = 1.118·10⁻⁵ · r · rpm²

Worth telling students once

The mistakes this practical produces every year

Hydrate molar masses are the single most common source of a wrong weigh-out in first-year reports. The weigh-out calculator flags a hydrate when it recognises one.

Every calculator shows its substitution, so a demonstrator can see where a student went wrong rather than only that they did.

For the person running the course

If you want this page named for your course

What it costs

Nothing, for you and for your students, permanently. There is no licence to sign, no account for students to create, no data to hand over, and nothing for your IT department to approve or install.

What you would get

A page named for your course, with your calculations in your order and your conventions, at a stable URL you can paste into your course management system once and reuse every year.

What we would like back

To be told when it is wrong. If a value, a convention, or a hazard note does not match how your course teaches it, that is a bug worth fixing.

Ask for a page for your course

The honest caveat

Aliquot is an educational aid, not a safety authority and not a certified instrument. Students should verify critical values and follow the safety data sheet and your institution's protocols.

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