Chem exam #4

Endothermic vs. Exothermic processes

Endothermic: absorbs heat (melting, evaporation, Boiling water)

 Exothermic: releases heat (condensation, combustion, Burning wood or paper Candle burning)'

Formula for internal energy change (ΔE)  

The formula for internal energy change (ΔE) is ΔE = q + W, where q represents the heat added to the system and W is the work done on the system.

When energy is entering the sytem ΔE is what

greater than zero

ΔE surroudings 

heat gained by surroundings (positive) 

When energy is leaving the system ΔE is what

less than zero

ΔE system

heat released by system (negative)

Equation for when Heat absorbed/released by a substance

q = m · Cs · ΔT

  ⁠◦  m = mass (g), Cs = specific heat, ΔT = Tfinal – Tinitial.

Thermal equilibrium principle

q of the heat lost + q heat gained = 0

lost = higher inital temp

gained = lower inital temp

Diamagnetic vs. Paramagnetic

Diamagnetic: all electrons paired (Zn, Cd²⁺).

Paramagnetic: unpaired electrons (Fe²⁺, Cu²⁺).

How to find atomic radius 

left —> right decreases

top —> bottom increases 

How to find ionic radius

less protons = higher ionic radius

more protons = lower ionic radius

How to find metallic character 

left —> right decreases

top —> bottom increases 

Node definition

point where there is no probability of finding an electron 

S orbital (holds 2 electrons)

p orbital (holds 6 electrons)

d orbital (holds 10 electrons)

f orbital (holds 14 electrons)

Bomb calorimeter equation

qcal = Ccal · ΔT which gives you Qrxn

convert mass of compound to mol

use ΔErxn = qrxn / mol compound.

What does Hess’s Law say?

You can add or subtract known reactions to get a new one, and add/subtract their heats (ΔH) the same way.

Photon energy equation

E = (hc)/λ

  ⁠◦  Use for wavelength/energy conversions.

  ⁠◦  h = Planck’s constant, c = speed of light.

Energy per mole of photons

Multiply E (per photon) × Avogadro’s number (6.022 × 10²³).