Teach & case
Help a near-peer reason through the idea — when you explain it, you understand it best — then read the real decision it comes from.
Help Halden with the moles
What you've shown you can teach
A real case · you decide
Halden and the doubled recipe
Halden — a student scaling up a lab reaction and unsure how to read the balanced equation
Halden needs to react hydrogen with nitrogen to make ammonia: N₂ + 3H₂ → 2NH₃. He reads "1 to 3" and grabs 1 gram of N₂ and 3 grams of H₂. Something feels off when the numbers don't work out.
The coefficients (1, 3, 2) are a MOLE ratio: 1 mole N₂ reacts with 3 moles H₂. Moles count particles, not grams — and a mole of N₂ weighs 28 g while a mole of H₂ weighs about 2 g.
So "1 to 3 by moles" is NOT "1 g to 3 g." By mass it's 28 g of N₂ to 6 g of H₂. Reading the ratio as grams silently changes the whole reaction.
The equation says N₂ + 3H₂. Does that mean 1 gram of N₂ per 3 grams of H₂?
Halden has 2 moles of N₂. How much H₂ does he need — and why not just "3"?
Halden re-weighs by moles: 28 g N₂ to 6 g H₂, not 1 to 3. That's Halden's whole point: a balanced equation is a recipe in MOLES, and grams only enter when you finally step on the scale.