Chemistry homework often goes wrong at a small transition: changing grams into moles, reading a subscript as a coefficient, or using the wrong volume. Good help makes those steps visible so you can check them yourself.
By the Apex Vision team · 6 minute read. We publish Apex Vision AI. This guide uses official resource descriptions and original worked examples with checked calculations; it does not claim a controlled accuracy test of the tools.
Useful chemistry homework resources
| Resource | Useful for | Access | Your check |
|---|---|---|---|
| OpenStax Chemistry 2e | Explanations, worked examples and practice | Free online textbook | Match the chapter and method to your course |
| PhET | Visual practice with concepts such as balancing | Free interactive simulations | Explain what changes and what stays conserved |
| Wolfram Alpha | Specified equations, chemical data and calculations | Free queries; some features require Pro | Correct formulas, amounts and units |
| Apex Vision AI | Explaining a question or equation on screen | 30 free responses to start; free access refills every 12 hours | Accurate reading of subscripts, charges and values |
Use a reference to learn the method and a calculation tool to check the arithmetic. Neither can fix an incorrectly copied chemical formula without enough context.
Worked example: from grams to product yield
For a paper calculation, suppose 4.86 g of magnesium reacts completely with excess oxygen to form magnesium oxide. Find the theoretical mass of MgO. Use the supplied rounded molar masses: Mg = 24.3 g/mol and MgO = 40.3 g/mol.
1. Balance the equation. Start with Mg + O₂ → MgO. The balanced form is:
2Mg + O₂ → 2MgO
There are 2 Mg atoms and 2 O atoms on each side. Change coefficients to balance an equation; changing a subscript would change the substance.
2. Convert the known mass to moles.
4.86 g Mg × (1 mol Mg / 24.3 g Mg) = 0.200 mol Mg
3. Use the mole ratio. The coefficients give 2 mol MgO / 2 mol Mg, so 0.200 mol Mg produces 0.200 mol MgO. The two coefficients cancel; they do not mean you should double the product amount.
4. Convert product moles to mass.
0.200 mol MgO × 40.3 g MgO/mol MgO = 8.06 g MgO
Answer: 8.06 g MgO, to three significant figures using the supplied molar masses.
Check: the product is heavier than the starting magnesium because it also contains oxygen. It includes 8.06 − 4.86 = 3.20 g of oxygen. This is a theoretical yield: an actual collected mass can be lower. If oxygen were not in excess, you would first need to identify the limiting reactant.
The general route is grams of known substance → moles → mole ratio → grams of requested substance. OpenStax explains reaction stoichiometry; the numbers above are an original practice example.
Quick example: use the final solution volume
A solution contains 0.0500 mol of dissolved solute in a final solution volume of 250.0 mL. What is its molarity?
250.0 mL = 0.2500 L
M = moles of solute / liters of solutionM = 0.0500 / 0.2500 = 0.200 mol/L
Answer: 0.200 M.
The denominator is the final solution volume, not just the amount of solvent added. Also check the unit conversion: dividing by 250.0 instead of 0.2500 would make the numerical answer 1,000 times too small. See OpenStax’s molarity chapter.
How to use each resource
OpenStax: learn the method
Chemistry 2e organizes explanations and worked examples by topic. Start with the step you cannot justify, such as choosing a mole ratio or writing an equilibrium expression.
After reading an example, attempt a different problem without copying the solution. Keep your course’s required conventions and rounding rules.
PhET: make balancing visible
PhET’s Balancing Chemical Equations provides visual practice with coefficients and atom counts.
Predict which coefficient needs changing, then check both elements again. This is especially useful if the symbolic equation feels disconnected from the particles it represents.
Wolfram Alpha: check the calculation
Wolfram Alpha’s reaction tools cover balancing and stoichiometry. Supply the exact formulas and amounts, including units.
Read its interpretation of your input before trusting a result. A missing subscript or charge can describe a different problem.
Apex Vision AI: discuss a question on screen
Include the complete question and readable chemical notation. Ask Apex Vision to read back formulas, charges and the requested quantity before explaining a solution.
Use the extension guide to get started, then compare the proposed method with your textbook and your own calculation.
Five checks before you submit
- Formulas and charges: verify every subscript, coefficient, ionic charge and state symbol required by the question.
- Balanced equation: count each element on both sides. For an ionic equation, check total charge as well.
- Units: write them through the calculation and confirm that unwanted units cancel.
- Assumptions: identify excess or limiting reactants, the stated conditions and any idealizations.
- Reasonable result: check magnitude, significant figures and whether the answer addresses the requested quantity.
“Read back the formulas and given quantities. Help me identify the type of problem, then show one step at a time with units. Explain the mole ratio and give me an independent check. Do not assume a missing quantity.”
For laboratory reports, use your actual observations and measurements. A worked example or generated value is not experimental data. Follow your instructor’s rules for outside help and use the assigned laboratory procedure for any practical work.
Frequently asked questions
What are good free resources for chemistry homework help?
OpenStax offers a free chemistry textbook with explanations and worked examples, and PhET offers free simulations. Wolfram Alpha provides free queries with some paid features, while Apex Vision provides free starter responses. Choose based on whether you need a concept explained, visual practice or a calculation check.
Can AI balance chemical equations and solve stoichiometry?
It can help, but verify the formulas and count atoms yourself. For stoichiometry, use a balanced equation, convert to moles before applying a mole ratio, and check the limiting reactant when necessary. A fluent explanation does not guarantee correct chemistry or arithmetic.
Can I use these resources for AP or college chemistry?
They can support many introductory chemistry topics, but coverage and depth vary. Match the resource to your syllabus and your instructor’s required method. Advanced organic, analytical or physical chemistry problems may need a more specialized reference or individual help.
Why do two chemistry helpers give different answers?
Compare the chemical formulas, units, balanced equation, molar masses, limiting-reactant assumption and rounding. For solutions, check whether both calculations use the same final volume and concentration definition. Resolve those differences before choosing an answer.
Sources and review notes
Reviewed October 13, 2026 against the official OpenStax, PhET and Wolfram Alpha pages linked above. The numerical examples are original and their arithmetic has been checked. Product descriptions are not claims of perfect accuracy or a guarantee of a correct assignment.