mecce

chemical reaction w positive H

endothermic reaction

motion of object

kinetic energy

exo vs endo: sweat evaporates from skin

endo

• absorb/remove heat, cools down

exo vs endo: gasoline burning

exo

• release energy = temp rise

exo vs endo: dissolving CaCl2 in water!

exothermic

• heat is released when solid dissolved

exo vs endo: water freezing in freezer

exothermic

• water loses its heat = less KE to make solid

change in enthalpy symbol

triangle H

draw exo vs endo

yeah

if same heat added to 100g of Au, Cr, and Hg, all at same temp start, which’ll be hottest

Hg

6Fe + 4O2 = 2 FE3O4 | 1787 kJ released every 6mol of Fe

• how much kJ energy released for each Fe3O4 mol produced?

1787kJ / 2 mol Fe3O4 = 893.5kJ/mol

22.1g copper at initial temp 19.6deg dropped in cup calorimeter has 31.3g of water at initial temp of 75.2deg, what is system final temp when copper/water in thermal equilibrium

(22.1)(.385)(Tf-19.6) + (31.3)(4.184)(Tf-75.2)=0 | 71.8C

3.82g of Mg nN3- reacts w 7.73g of water

• what reactant is limiting

3.82g MgN ⋅ (1molMgN / 100.95gMgN) = .0378mol MgN

.0378molMgN ⋅ (3molH2O / 1mol MgN) = .114 H2O

7.73g H2O ⋅ (1mol H2O / 18.02g H2O) = .429mol H2O

.429mol H2O ⋅ (1mol MgN / 3mol H2O) ⋅ (17.04g NH / 1mol NH) = .143mol MgN

• Mg3N2 = limiting reactant

3.82g of Mg nN3- reacts w 7.73g of water

• how many NH3 (ammonia) can be produced

.0378mol MgN ⋅ (1mol NH / 1mol MgN) ⋅ (17.04g NH / 1mol NH) = 1.29g NH

3.82g of Mg nN3- reacts w 7.73g of water

• how many excess reactant g left over

.429 - .114 = .315

.315mol H2O ⋅ (18.02g / 1mol H2O) = 5.68g H2O

Octane combustion

• Y/N = downhill/exothermic//E spread

NO

Octane combustion

• disorder/matter spread

YES

Octane combustion

• spontaneous natural process

YES

Octane combustion

• exo or endo

EXO

exo vs endo

• CO = C + G

endo

exo vs endo

• 2H + O = H2O

exo

exo vs endo

• Na + Cl = NaCl

exo

why is sweating natural way for body to cool itself

• sweat evaporates from skin

• it absorbs excess H E from body to change from liquid-vapor

• lower skin temp

whats endo reaction

reaction absorb E from surroundings

whats exo reaction

reaction release E into surroundings

13.8g Z heated to 98.8C bioled water + dropped to 45g water at 25C, when water/zinc go thermal equaal = 27.1C | What’s Z specific heat?

qwater = (45g)(4.18J/g°C)(27.1−25.0) = 395.01J

Szn = qzn / mzn triTzn = (-395.01) / (13.8)(27.1-98.8) = .399 J/g°C

what’s calorimetry

• technique to get E amount absorbed/released in Rxn