important formulas

Question 1

what is the formula for calculating a weighted average?

Answer 1

weighted average = [(mass isotope1)(% isotope 1/100)]+[(mass isotope 2)(% isotope 2/100)]

Question 2

what is the Rydberg formula? when is it used?

Answer 2

• ΔE=R(sub)H[(1/nf^2)-(1/ni^2)]
  -calculating energy transitions

Question 3

-what is the formula for calculating wavelength?

Answer 3

E(photon)=hc/λ
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Question 4

what is the formula for percent composition?

Answer 4

percent composition by mass= (mass of one element/total mass of the sample)*100

Question 5

what is the equation for the first law of thermodynamics?
what does each variable mean?

Answer 5

ΔE= q + w
-q= amount of thermal energy transferred
-w= amount of work involved

Question 6

what is the formula for calculating heat gained or lost?

Answer 6

q=cmΔT

Question 7

what formula would you use for a bomb calorimetry problem using the first law of thermodynamics?

Answer 7

q(calorimeter)+q(reaction)=0

Question 8

what is the formula for calculating formal charge?

Answer 8

formal charge = valence electrons - nonbonding electrons - (bonding electrons/2)

Question 9

what is the formula for bond order?

Answer 9

bond order = 1/2(# of bonding electrons - # of antibonding electrons)

Question 10

what is the formula for the ideal gas law?

Answer 10

PV=nRT

Question 11

what is the formula for the combined gas law?

Answer 11

(P1V1)/T1=(P2V2)/T2

Question 12

what is the equation for molar speed?

Answer 12

u(rms)= sqrt[(3RT)/MM]