Hope that this helps, lmk if you need clarification
What about it?? What’s the question?
Answer:
mass = 17.2 grams
Explanation:
q = mcΔT => m = q/cΔT = 187j / (0.90j/g°C)(35.6°C - 23.5°C) = 17.2g
Answer: Kb = 3.15 × 10 ⁻⁴
Explanation:
This is how you calculate Kb for this reaction.
1) Equilibrium equation:
CH₃NH₂ + H₂O ⇄ CH₃NH₃⁺ + OH⁻
2) Kb = [CH₃NH₃⁺] [OH⁻] / [CH₃NH₂] ↔ all the spieces in equilibrium
3) From the stoichiometry [CH₃NH₃⁺] = [OH⁻]
Then, Kb = [OH⁻] [OH⁻] / [CH₃NH₂] = [OH⁻]² / [CH₃NH₂]
4) You get [OH⁻] from the pH in this way:
pOH + pOH = 14 ⇒ pOH = 14 - pH = 14 - 11.40 = 2.60
pOH = - log [OH⁻] = 2.60 ⇒ [OH⁻] = 10^(-2.6) = 0.002512
5) [CH₃NH₂] in equilibrium is given: 0.0200M
6) Now compute:
Kb = (0.002512)² / 0.0200 = 3.15 × 10 ⁻⁴