High School Chemistry Tutoring

High school chemistry is often the first science class that asks for real math. Students who did fine in biology meet scientific notation, unit conversions, and word problems about moles. Many Texas students take chemistry in grade 10 or 11, often alongside geometry or Algebra II. A missed idea early on, like what a mole is or how to read the periodic table, quietly breaks the units that follow. One-on-one tutoring from STEM Tutor 360 goes back to the missing idea, rebuilds it, and then moves forward with your class.

Sessions follow your own course, whether it is on-level, honors, or pre-AP. Bring the unit you are in, the worksheet that did not make sense, or the test you just got back. We work problems on a shared whiteboard, and you do much of the writing, because chemistry is learned by solving problems. Before a unit test, your tutor builds a practice set from your notes and quizzes, and you work it under time.

A typical high school chemistry problem, worked

Zinc reacts with hydrochloric acid: $\ce{Zn + 2HCl -> ZnCl2 + H2}$. A student mixes 10.0 g of zinc with 10.0 g of $\ce{HCl}$. Which reactant runs out first, how many grams of hydrogen form, and how much zinc is left over?

The equation compares moles, not grams, so convert first. Zinc: $\dfrac{10.0\ \text{g}}{65.38\ \text{g/mol}} = 0.1530\ \text{mol}$. $\ce{HCl}$: $\dfrac{10.0\ \text{g}}{36.46\ \text{g/mol}} = 0.2743\ \text{mol}$. Each mole of zinc needs 2 mol of $\ce{HCl}$, so 0.1530 mol of zinc would need 0.306 mol of $\ce{HCl}$. Only 0.2743 mol is there, so $\ce{HCl}$ is the limiting reactant. The two masses were equal, so comparing grams would not have told us this.

Now let the limiting reactant set the amounts. Hydrogen: $$0.2743\ \text{mol}\ \ce{HCl} \times \dfrac{1\ \text{mol}\ \ce{H2}}{2\ \text{mol}\ \ce{HCl}} \times 2.016\ \text{g/mol} = 0.276\ \text{g}$$ Zinc used: $$0.2743\ \text{mol}\ \ce{HCl} \times \dfrac{1\ \text{mol Zn}}{2\ \text{mol}\ \ce{HCl}} \times 65.38\ \text{g/mol} = 8.97\ \text{g}$$ So $10.0\ \text{g} - 8.97\ \text{g} = 1.03\ \text{g}$ of zinc is left over.

Where students usually get stuck

• Putting grams into a mole ratio. The balanced equation compares moles, so convert first.
• Skipping the balancing step, which makes every ratio after it wrong.
• Using the atomic number instead of the atomic mass when finding molar mass.
• Gas law units. Temperature must be in kelvins, and the pressure and volume units must match the value of R.
• Lewis structures that start from the wrong electron count. Add up the valence electrons first.
• Lab write-ups with data but no reasoning. A conclusion needs a claim, evidence from your data, and an explanation.

Lab reports and unit tests

Most lab reports follow one pattern: purpose, data, calculations, and a conclusion that uses the data. We go through your own results, check the calculations and units, and talk about sources of error. Then you write the report yourself. For unit tests, we find the problem types you keep missing and practice those until they feel routine.