Sig Figs/Polyatomic Ions
In a number which digit holds the uncertainty?
The last one
What is molar mass?
The grams of an element in one mol of that substance. ie. H=1.01 g/mol
- allows us to accurately compare the masses of different elements
What is Boyle's Law?
Volume and Pressure are inversely related
- as one goes up the other goes down
What is q?
heat
- energy transferred between a system and its surroundings
What is an orbital?
electron "cloud"
- a space surrounding the nucleus where electrons are likely to be found
What is the rule when adding or subtracting?
Keep the number of decimal places as the number with the least decimal places
What is the conversion factor for *C to K?
K=*C + 273
What is the conversion factor for mmHg/torr -> atm?
760 mmHg/torr = 1 atm
What is it mean for a reaction to be exothermic?
the reaction releases energy into the environment
- the reactants had more energy than the products ie. water freezing into ice
What is Aufbau's Principle?
orbitals fill up in a certain order
- 1s, 2s, 2p, etc.
Are leading zeros (before the first integer) significant?
No, but trailing zeros (after the last integer) are
When setting up the conversion how do you get the units to cancel out?
Same units in numerator and denominator
Ex) 4232 sec -> hours
4232 sec x 1 min x 1 hour. = 1.716 hours
60 sec. 60 min. *4 sig figs*
What is R?
Ideal gas constant
0.0821 atmL/molK
What is c?
specific heat capacity
- different for every substance
- amount of energy required to increase the temperature of 1g of the substance by 1K
What is Pauli's Exclusion Principle?
within each orbital (which can hold 2 electrons) one electron must have a positive spin (up) and one electron must have a negative spin (down)
What is the chemical formula of carbonate?
CO3^2-
What is the percent yield?
actual/theorhetical x 100
What is the ideal gas law and what does each variable stand for?
PV=nRT
P = pressure
V = volume
n = mol
R = ideal gas constant = 0.0821 atmL/molK
T = Temperature (in K)
What is H?
enthalpy
- the heat of the reaction on a per mole basis
- solve for heat by using q=mc(deltaT) then divide by the moles of the substance
What is the difference between a full electron configuration and a condensed electron configuration?
- full electron configuration includes ALL of the levels
- condensed electron configuration refers back to the closest noble gas the lists whatever levels are remaining
- the exponents should add up to the atomic # (# of electrons)
What is the name of the following compound?
NaCN
Sodium Cyanide
0.750 mol Cl2 reacts with 3.00 mol F2 to form ClF3. What is the limiting reactant?
Cl2 + 3F2 -> 2ClF3
convert Cl2 and F2 to mol ClF3 using ratio from equation
0.750 mol Cl2. x 2 mol ClF3. = 1.50 mol ClF3
1 mol Cl2
3.00 mol F2 x 2 mol ClF3. = 2.00 mol ClF3
3 mol F2
Cl2 is the limiting reactant because 1.50 mol < 2.00 mol
A 1.20L balloon is filled with 0.400 mol O2 at 23*C. What is the pressure within the balloon in atm?
PV=nRT
V = 1.20L
n = 0.400 mol
R = 0.0821 atmL/molK
T = 23*C + 273 = 296K
P = nRT/V
(0.400mol x 0.0821 atmL/molK x 296K)/1.20L = 8.10 atm
250.g of Fe is heated from 25*C to 117*C. The specific heat capacity of Fe is 0.450 J/gK. What is the heat of the reaction (in J) and is it endothermic or exothermic?
q=mc(delta T)
m = 250. g
c = 0.450 J/gK
delta T = 117-25 = 92K (don't need to convert because you could be adding 273 to each value)
q= 250. g x 0.450 J/gK x 92K = 10,350J -> 10,400J (3 sig figs)
this reaction is endothermic because q is positive and the system must absorb heat to increase the temperature of the Fe
What is the full and condensed electron configuration for Br-?
full: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
condensed: [Kr]