University:
Ontario Tech University
Course:
CHEM1010U | Chemistry I
Academic year:

2024
Views:

444

Pages:

5
Author:

Avneet S.

**Chemistry Lecture #4** **Chp.3 Mole Relationships in Chemical Reactions** Mole is used to represent molecules. **Do we have enough molecules to collide?** **Ex:** Cl₂ Diatomic molecule (2 of them) **Unbalanced** or unbalanced mentioned in 9/1 **Balance Chemical Reaction** 2Na + Cl₂ → 2NaCl **Subscripts** change the identity of molecules **Coefficients (# of moles) x2Cl** Only thing that can change **H₂O and H₂O** Only use whole #'s (ideally) Ex: 2/0.5 x 2 Use multiplication to get rid of fractions 20.1 x 10^23 molecules 6.02 x 10^23 atoms/molecule **Check your answer to make sure it's correct** If not possible to balance, move to next one and use a 1:1:1 ratio. **# of moles that can react** **Balance Eq:** 2NaBr + Cl₂ → 2NaCl + Br₂ **Balanced Eq:** doesn't include states right now **Steps:** * Add 2 in front of 2NaBr, changed # of Sodiums * Add 2 in front of NaCl, changed # of Chlorine **Menti Problem / Balance Eq:** 4NH₃ + _Cl₂ → _N₂ + _NH₄Cl * Don't need coefficients * Sub of coefficients = 8 **Stoichiometry (CHEM math)** (convert from molecules A -> molecule B, conversion unit -> moles) grams A <---> moles A <---> moles B <---> grams B molar mass(A) ratio molar mass(B) Salicylic acid (SA) Acetic acid (AA) **SA + AA → C₉H₈O₄ + CH₃COOH** **C₇H₆O₃ + C₂H₄O₂ → Aspirin + Acetic acid** Eq. is balanced How many grams of AA are needed to react with 4.5g of SA? **4.5g of SA needs:** * Moles of SA = mass ÷ molar mass * Moles of SA = 4.5g ÷ 138.07 g/mol * Moles of SA = 0.033 mol **Molar ratio 1:1 ratio** Moles of AA = Moles of SA = 1 **Mass of AA = Moles of AA x molar mass** **Mass of AA = 0.033 mol x 102.09 g/mol** **Ans:** 1. **Calculate moles of SA:** Moles of SA = mass ÷ molar mass = 4.5g ÷ 138.07 g/mol = 0.033 mol