Chemistry homework help with units and sig figs in every step
Most chemistry mistakes are not about chemistry: a unit that was never cancelled, a mole ratio flipped, or the wrong number of significant figures. Send your problem and attempt, and your agent works through it with dimensional analysis, shows each conversion factor, checks the math in Python and explains the concept behind it.
The prompt
- Help me with this chemistry homework: [PROBLEM OR PHOTO]. I am taking [COURSE]. Here is what I tried: [MY WORKING]. Solve it with dimensional analysis, writing every conversion factor with units so I can see them cancel. Use molar masses from the periodic table to two decimals and say which values you used. Give the final answer with correct significant figures and explain why. Check the arithmetic by calculation. Tell me which concept this problem tests ([TOPIC] if I know it) and the one mistake students make most often here. Finish with a similar problem with different numbers, and only show its answer after I reply.
What to change
- [PROBLEM OR PHOTO]: Type the problem or attach a photo of the worksheet, and say which number.
- [COURSE]: E.g. "high school chemistry", "AP Chemistry", "General Chemistry I", "IB Chemistry SL".
- [MY WORKING]: Type your steps or attach a photo. "Not started" is fine.
- [TOPIC]: E.g. "limiting reactant", "ideal gas law", "molarity", "pH". Or leave it out.
Example result
- Problem 7
- 2.00 g of hydrogen gas reacts with 2.25 g of oxygen gas to form water. Which is the limiting reactant, and what mass of water forms?
- Step 1: balanced equation
- 2 H2 + O2 → 2 H2O
- Always balance first. The mole ratios come from these coefficients.
- Step 2: grams to moles
- • H2: 2.00 g × (1 mol / 2.02 g) = 0.990 mol H2
- • O2: 2.25 g × (1 mol / 32.00 g) = 0.0703 mol O2
- Step 3: find the limiting reactant
- • O2 needs 2 mol H2 per mol: 0.0703 mol O2 × (2 mol H2 / 1 mol O2) = 0.141 mol H2 needed
- • We have 0.990 mol H2, far more than needed, so O2 is the limiting reactant.
- Step 4: moles of water from the limiting reactant
- 0.0703 mol O2 × (2 mol H2O / 1 mol O2) = 0.1406 mol H2O
- Step 5: moles to grams
- 0.1406 mol × (18.02 g / 1 mol) = 2.53 g H2O
- Significant figures
- The given masses have 3 sig figs (2.00 and 2.25), so the answer has 3: 2.53 g of water.
- Your attempt
- In step 2 you wrote (1 mol O2 / 2 mol H2O), upside down. Write the unit you want on top and the unit you want to cancel on the bottom, then the units tell you if the ratio is right.
- Concept tested
- Limiting reactant: the reactant that runs out first decides how much product forms, not the one with the smaller mass.
- Your turn
- 4.00 g of aluminum reacts with 5.00 g of chlorine gas: 2 Al + 3 Cl2 → 2 AlCl3. Find the limiting reactant and the mass of AlCl3. Reply with your answer.
How to do it with todo.is
- Copy the to-do and replace the brackets with the problem, your course and your attempt.
- Paste it into todo.is, or send it with a photo of the worksheet to your agent on WhatsApp or Telegram.
- Your agent sends a worked solution with every unit shown, sig figs explained and feedback on your attempt.
- Reply with your answer to the practice problem, or ask "explain moles like I'm new to this".
Tips for a better result
- Write units on every number, every time. If they do not cancel to the unit you want, the setup is wrong before you touch the calculator.
- Balance the equation before anything else. An unbalanced equation gives wrong mole ratios.
- Use the molar masses from your class periodic table and tell your agent if they round differently.
- Ask for a one-page cheat sheet PDF of the formulas from the chapter (PV = nRT, M = mol/L, pH = −log[H+]) to study from.
chemistry homework help: FAQ
- What chemistry topics can it help with? Stoichiometry, moles, limiting reactants, gas laws, solutions and molarity, acids and bases, thermochemistry, equilibrium, kinetics, naming compounds and Lewis structures, up to first-year university level.
- Can it read a photo of my chemistry worksheet? Yes. Send a clear photo and say which problem. Subscripts in formulas can be hard to read in handwriting, so your agent repeats the problem back if anything is unclear.
- Does it get significant figures right? The prompt asks it to state the sig figs and the rule it used. Teachers sometimes have their own rounding rules, so check it against your class notes.
- Can it help with organic chemistry mechanisms? It can explain mechanisms step by step in words, with arrow-pushing described for each step. For drawings, use your textbook or class software alongside the explanation.
JavaScript is required to use the todo.is app.