Question 1

What is VerChem?

Accepted Answer

VerChem is a free chemistry platform offering deterministic calculators, a 2D structure editor with substructure and similarity search, spectroscopy and lab-safety references, an interactive periodic table with all 118 elements, and a database of 1,311 compounds. Published element references include IUPAC and NIST. Built for students, chemists, and engineers.

Question 2

Is VerChem free to use?

Accepted Answer

Yes. The chemistry tools are free to use, with no per-calculation charge and no paid tier gating the chemistry itself.

Question 3

How accurate is VerChem data?

Accepted Answer

VerChem cites published reference sources: standard atomic weights are based on the IUPAC 2021 table, while selected physical properties cite NIST and the CRC Handbook. VerChem is not certified by those organizations, and property coverage varies by element.

Question 4

What calculators does VerChem offer?

Accepted Answer

VerChem offers 8 chemistry calculators: Molar Mass, Equation Balancer, Stoichiometry (8 modes), pH Calculator (11 modes), Gas Laws (9 modes including Van der Waals), Thermodynamics, Chemical Kinetics, and Electrochemistry. Plus interactive tools: 3D Molecular Viewer, Lewis Structures, VSEPR Geometry, and a table covering all 118 elements.

Question 5

How do I calculate molar mass?

Accepted Answer

Enter a supported chemical formula (e.g., H2SO4, NaCl, C6H12O6) into the Molar Mass Calculator. It calculates molar mass by summing standard atomic weights × subscripts. For H2O: (2 × 1.008) + (1 × 15.999) = 18.015 g/mol. The standard atomic weights are based on the IUPAC 2021 table.

Question 6

How do I balance a chemical equation?

Accepted Answer

Enter your unbalanced equation (e.g., H2 + O2 -> H2O) into the Equation Balancer. It uses algebraic matrix methods to find the smallest whole-number coefficients. The balanced result: 2H2 + O2 -> 2H2O. Works for redox, combustion, synthesis and decomposition reactions written in molecular form; ionic half-equations with charges are not supported.

Question 7

What is the Ideal Gas Law formula?

Accepted Answer

The Ideal Gas Law is PV = nRT, where P = pressure, V = volume, n = moles of gas, R = gas constant (8.314 J/mol·K or 0.0821 L·atm/mol·K), and T = temperature in Kelvin. VerChem Gas Laws Calculator supports 9 modes including Combined Gas Law and Van der Waals equation.

Question 8

How do I calculate pH from concentration?

Accepted Answer

pH = -log[H+]. For a 0.01 M HCl solution: pH = -log(0.01) = 2. For bases, calculate pOH first, then pH = 14 - pOH. VerChem pH Calculator handles strong/weak acids and bases, buffer solutions, and shows visual pH scale.

Question 9

How many elements are in the periodic table?

Accepted Answer

There are 118 confirmed elements. Elements 1-94 occur naturally (though some like Technetium and Promethium are extremely rare). Elements 95-118 are synthetic, created in laboratories. The latest additions (Nihonium, Moscovium, Tennessine, Oganesson) were confirmed by IUPAC in 2016.

Question 10

What are rare earth elements?

Accepted Answer

Rare earth elements include 17 elements: Scandium (Sc), Yttrium (Y), and the 15 Lanthanides (La-Lu: Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutetium). Despite the name, most are not rare but are difficult to separate from each other.

Question 11

What is a limiting reagent?

Accepted Answer

A limiting reagent is the reactant that is completely consumed first in a chemical reaction, determining the maximum amount of product that can be formed. VerChem Stoichiometry Calculator identifies the limiting reagent and calculates theoretical yield, actual yield, and percent yield.

Question 12

How do I convert moles to grams?

Accepted Answer

Mass (g) = Moles × Molar Mass (g/mol). For example, 2 moles of water: 2 mol × 18.015 g/mol = 36.03 g. To convert grams to moles, divide: Moles = Mass / Molar Mass.

Question 13

How is VerChem different from asking an AI chatbot for a chemistry calculation?

Accepted Answer

VerChem computes with deterministic engines rather than a language model. The same input always produces the same output. An optional Verified Answer Card records the exact inputs, semantic engine release, output, textbook citation, AI explanation, and an Ed25519 compact JWS covering them so the engine fields can be replayed and compared later. Anyone can verify that JWS independently against VerChem's published public key instead of trusting a server-reported validity result. Signature integrity and current-engine agreement are reported separately; cards from replaced releases are marked superseded or corrected instead of current VERIFIED. A chatbot writes its answer as text: it can vary between runs and leaves no record to re-check.

Question 14

Is a VerChem result guaranteed to be correct?

Accepted Answer

It is reproducible, not infallible. A VerChem calculation is deterministic — identical inputs always give identical output — and cites published element references including IUPAC and NIST. Required physical inputs such as solution density or a reaction-specific equivalents factor must be supplied; calculations that need a missing value are rejected rather than guessed. Any listed assumptions describe the declared model scope. Verified Answer Cards are tamper-evident: any later edit breaks the signature. That signature proves the signed record was not altered; current validity is a separate replay check, and neither property proves the chemistry model applies to your situation.

Hydrogen Sulfide

Chemical Properties

Physical Properties

Safety Information

GHS Pictograms

Hazard Statements

Uses & Applications

Related Compounds

Calculate with Hydrogen Sulfide

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