DAT GenChem Flash Cards

determine the number of moles

mass in grams/ molecular weight

Density= ? unit

mass kg/ volume m3 (convert to g/cm3 divide by 1000) or g/cm3 (to convert to kg /m3 multiple by 1000)

3rd quantum number

ml dependent on l ex. l=2 ml= -2,-1,0,1,2

a sample of hydrated magnesium sulfate MgSO4* XH2O, weighs 21 g. it is paced inside of an oven until all of the water is vaporized the anyhydrous form weighs 12 g, what is the value of x in the hydrated salt? MgSO4= 120

mol H2O/ mol of MgSO4 find the mol of H2O 21-12= 9 grams of H2O 9g/ 18g H2O= 0.5 mol of H2O only do the salt not considering the water. 12g / 120g MgSO4= 0.10 mol 0.5 mol/ 0.10 mol= 5 the x is 5

for hydrated salt problems remember the formula

mol H2O/ mol substance hydrated

how do you calculate the energy of electron going from 3-->2

(-2.178x10e-18)/(2e2) - (-2.178x10e-18)/(3e2)=

the mass defects of helium nucleus 5x10-29 kg. What is the nuclear binding energy ?

(5x10e-29) (9x10e-27)= 4.5x 10e-12 J

Diamond density is 3,500 kg/m3 what is the volume in cm3 of 1 3/4 carat (1 carat= 0.2)?

0.1 cm3

convert amu to kg

1 amu = 1.66x10e-27 kg

convert Ev to J

1 ev= 1.6 x10e-19 J

convert kg to joules

1 kg = 9x10e16 J

how many atoms are in 1 mole?

1 mole= 6.02x10e23 atoms

What are the coefficients that must be used to balance the combustion of butane? C4H10+O2 --> CO2+ H2O

1) always leave the oxygen until the end and work with the other elements. when your done balancing and the oxygen is not balanced then put the number of oxygen you get and multiple the rest by 2 C4H10 +O2 --> 4CO2 + 5H2O The number of oxygen is not balanced you have 13 oxygen on the product. multiple the reactant oxygen by 13 and the rest by 2. 2C4H10 + 13O2 --> 8 CO2+ 10H2O

What are the rules to assigning oxidation states?

1) the oxidation state of any element in its standard state is 0 2) the sum of oxidation states of the atoms in neutral molecules is 0 3) Group 1 have oxidation state of +1. Group 2 have oxidation state of +2 4) Fluorine has -1 oxidation state 5) hydrogen has +1 oxidation state when bonded to something more electronegative than carbon and -1 when bonded to something less electronegative than carbon. 6) oxygen has -2 oxidation state 7) the rest of the halogens have -1 oxidation state and the atom of the oxygen family have -2.

How many grams of lead (II) sulfate (303g/mol) are needed to react with sodium chromate (162 g/mol) in order to produce 0.16 kg of lead(II) chromate (323 g/mol)

1) write chemical formula PbSO4 + NaCrO4--> PbCrO4 303g/mol 162g/mol (323g/mol) 0.162kg convert to g 162g 162/ 323= 0.5 mole PbSO4= 303 multiply by 0.5= 151

in air bags, the reaction of sodium azide (NaN3, 65g/mol) to form sodium and nitrogen gas is triggered by an electrical current thus expanding the air bag. If there are 65 grams of sodium azide in the air bag, how many moles of nitrogen gas are formed?

1) write the chemical reaction and balance 2NaN3--> 2Na+ 3N2 2) mole to mole ratio 1 mole NaN3 x 3N2/ 2NaN3 = 1.5 mole

Use percent composition to find empirical formula: 70% of Fe and 30% of oxygen what is the empirical formula?

1. assume its our of 100 grams of substance 70 grams Fe and 30 grams O 2. find the number of moles of Fe and O 70 g Fe/ 55.4 g/mol Fe= 5/4 30 gO/ 16 g/mol O= 15/8 3. Ratio of Fe to Oxygen 5/4/15/8= 5*8 /4*15= 2/3 empirical formula= Fe2O3

Stoichiometry and balanced equations 2Al + 6HCl--> 2AlCl3 +3H2 if 108 grams of aluminum metal are consumed how many grams of hydrogen gas will be produced?

1. determine the number of moles used from aluminum when you react 108 grams. 108 g Al/ 27g Al= 4moles Al 2. so 4 moles produce 6 moles of H2= 2(6)= 12g of H2. 3. you must multiple the number of moles by the grams of molecular formula.

find the percent composition of C4H4N2

1. get it into empirical formula divide by 2 C2H2N 2. molecular weight= 2(12)+2(1)+14= 40 3. %C = 2(12)/40= 24/40= 12/20= 60/100= %60 try to get denominator to 100 so its easy to determine the percent %H= 2(1)/40= 5% %N= 14/40= 14/40= 7/20= 35/100= 35%

what is the percent composition of glucose C6H12O6

1. notice that it can be reduced down to its empirical formula. divide by 6 CH2O 2. find molecular weight: 12+2(1)+ 16= 30 3. % C= 12/30= 2/5= 8/20= 40/100= 40% % H= 2(1)/30= 1/15

atomic weight example- boron-10.013 makes up 20% and boron-11.009 makes up 80% of naturally occuring boron. What is the atomic weight of boron?

10.013(.20)+ 11.009(.80)= 10.810 amu

1 L=? cm3

1000 cm3

A angstrom= ? m

10e-10

mili

10e-3

micro

10e-6

nano

10e-9

an atom whose nucleus contains 7 neutrons which has a mass number of 12 is an isotope of what element?

12-7= 5 Boron

1000 L= ? m3

1m3

what is the electron configuration of aluminum atom?

1s2 2s2 2p6 3s2 3p1

how many unspin paired electrons does oxygen have?

2 unspined pair electrons

how many moles of N2H4 are in a sample whose mass is 96 grams? and how many molecules?

2(14)+4(1)= 32 96/32= 3 moles (6.02x10e23 molecules)= 18.06x10e23 molecules

cesium 137 has a half life of 30 years. how long will it take for only 0.3 g to remain from a sample that had an original mass of 2.4 g?

2.4 -30-> 1.2 -30-> .6 -30-> .3 90 years

what is the percent composition by mass of each element NaN3

23+ 3(14)= 65g 23/65= 1/3 14(3)/65= 42/65

What is the percent by mass of water in the hydrate MgCl2* 5H2O?

24.3+ 2(35.5)+ 5[2(1)+16]= 185.3 90/185.3= 50% of water

vitamin B12 can be prepared from radioactive cobalt (Co-58) a known B+ emitter, and administered orally as a diagnostic tool to test for defects in intestinal vitamin B12 absorption. What is the daughter nucleus for B12?

27 Co --> 26 Fe

In a 3.21g sample of the hydrate , CuSO4 *10 H2O (339.8 g/mol), how many grams of water are expected?

3.21 CuSO4* 10H2O x (180 H2O/339.8 CuSO4*10H2O)

Limited reagent determine the limited reagent 2ZnS+3O2--> 2 ZnO+ 2SO2 97.5 g 32g

3mol O/ 2 mol ZnS= 1.5 mol of O2 and we only have 1 mole of O2

Radioactive calcium-47 a known B- emitter is administered in the form of 47CaCl2 by I.V as a diagnostic tool to study calcium metabolism. what is the daughter nucleus of Ca-47

47 (20) Ca--> (21) Sc + -1e

in which subshell the highest energy electron of indium (In) found?

5p

a radioisotope B12 contains a radioactive cobalt -58 is administered to diagnose a defect in a patients vitamin B12 absorption. If Co-58 has a half life of 72 days approximately what percent of the radioisotope will remain in the patient a year later?

72 x 5= 360 =1 year (1/2)e5 = 1/32= 3/100= 3%

a radioactive sample with an initial mass of 80 gram and a half life of 6 years will decay.

80--> 40 --> 20--> 10-->5 you keep taking the half of it

how many electrons are there in lead-204

82 electrons 82 protons 122 neutrons

what is the empirical formula of the compound that is by mass 90 percent carbon and 10 percent hydrogen?

90 g C/ 12g C= 30/4= 15/2 mole 10 g H/ 1 gH= 10 moles 15/2/ 10/1 = 15*1/10*2= 15/20 = 3/4 C3H4

americium 241 is used to provide intracavitary radiation for the treatment of maligancies. This radioisotope to undergo alpha decay. What is the daughter nucleus?

95 Am --> 93 Np + alpha (4 and 2 protons)

what is the sum ofcoefficient of the complete balanced equation from combusting C2H6O

Add the subscripts total= 9

a certain radioactive isotope is administered orally as a diagnostic tool to study pancreatic function and intestinal fat absorption. This radioisotope is known to undergo B- decay and the daughter nucleus is Xenon=131. What is the parent isotope.

Becareful because it is asking for the parent nucleus so you work backward for this problem. 53 I--> 54 Xe

know how to get molecular formula from structure

C6H7NO2

CS2 + 3O2 --> CO2 + 2SO2 how many grams of CS2 are needed to make 64 grams of SO2

CS2= (12)+ 2(32)= 76g SO2= 64 grams so we need to make 1 mole of SO2 from CS2 so half of CS2 must be used in this case. 38g of SO2

What are the exceptions to the electron configuration rules?

Chromium (Cr) Molydiumm (Mo) Copper (Cu) silver (Ag) and gold (Au) prefer a half filled or completely filled d orbitals.

What is the formula for the energy of a photon?

Ephoton= hf= h c/wavelength h= universal constant c= speed of light

2Al+ 6HCl--> 2AlCl3 + 3H2 how many grams of HCl are required to produce 534 g of Aluminum chloride?

HCl= 1+35= 36 AlCl= 27+3(35)= 133.5 find the number of moles and compare mole to mole ratios 534g AlCl3/133.5= 4 moles AlCl3 12 moles of HCl so 12*36= 438g of HCl are required.

find the oxidation state of the following formulas KMnO4 FeCl2 NO3- HNO2 O2 SF4 Fe3O4

KMnO4= +1 + x +4(-2)=0 Mn=+7 oxidative state FeCl2= x+ 2(-1) =0 Fe= +2 NO3- = x+ 3(-2)= -1 N=+5 HNO2= +1 + x +2(-2)= 0 N=+3 O2= 0 SF4= x +4(-1)= 0 S= 4 Fe3O4= 3x + 4(-2)= 0 Fe= +8/3

t=3t 1/2

N0 (1/2)e3= 1/8

What is the formula for half life?

N=N0 (1/2)t/t12

one of the naturally occuring radioactive series begins with radioactive 92U . it undergoes a series of decays one of which is alpha, beta, beta, alpha, alpha, alpha, alpha, alpha, beta, beta, alpha, beta, alpha, beta

Pb 82

16 protons, 17 neutrons and 18 electrons makes up which element?

S2- because we gained 2 electrons

The empirical formula of a compound is found to be CO3. What is the molecular formula?

The empirical formula is the simplified version of the molecular formula. usually divided by the greatest common factor. Here the O has 3 that means the Carbon originally had a 3 before it was divided out. C3O9 because x/3=3

A sample of chromium oxide is 76.5% chromium by weight. What is the simplest formula of the oxide?

They gave you a lot of choices but the only way to tackle this type of problem is to go through the answers until you get the correct answer. CrO3= (52)+3(16)= 100 52/100= 52% therefore this is wrong CrO= 52+16= 68 52/68x100 = 76.5% so you do mass of chromium over the molecular weight. you cant put chromium to 100 because you dont know the grams of oxygen.

what is the electron configuration of Cu+? of Cu2+? of Fe3+?

[Ar] 3d10 [Ar] 3d9 [Ar] 3d5

what is the electron configuration for Zn2+

[Ar]3d10

What is the electron configuration for Au

[Xe] 6s1 4f14 5d10

iodated oleic acid contains radioactive iodine-131, is administered orally to study a patients pancreatic function. If 131I has a half life of 8 days, how long after the procedure will the amount of 131I remaining in patients body to reduce 1/5 its initial value? 1-8->1/2 -8->1/4 -8->1/8

about 24 days

which of the following radioactive decay causes a change in the mass number of the parent nucleus ?

alpha decay= decrease neutrons/ decrease protons B-= decrease neutrons/ increase protons= 0 no change in mass B+= increase neutrons/ decrease protons electron capture= increase neutrons/ decrease protons

radioactive decay

altering the number of protons and neutrons in the nucleus or lowering their energy.

electron capture

another way for an unstable nucleus to increase the number of neutrons is to capture an electrons from the closes shell and convert it to a neutron. the resulting atomic number is 1 less than the parent nucleus.

nuclear binding energy delta m

m= (total mass of seperate nucleons)- (mass of nucleus) E= m c2 c= speed of light 3x10e8

a student weighs 20 grams of AU (density= 20 g*cm-3) and 20 g of Ag( density= 10g*cm-3), which metal occupies the greatest volume and how much volume does it occupy?

density= mass/ volume do this for both silver will occupy a greater volume (2cm3)

diamagnetic vs. paramagnetic

diamagnetic= an atom with all spins paired and atoms are repelled from the magnetic field. paramagnetic= not all atoms are equally paired. electrons attract to the magnetic field. Odd number of electrons is always paramagnetic

what is the empirical formula of C6H12O6 and K2S2O8

divide by 6 CH2O divide by 2 KSO4

Empirical formula

divide the greatest common factor of the subscripts in the formula

If compound X3P2 has a molar mass of 135 g/mol, what is the atomic weight of the unknown element x?

firs you know that 3(x) + 2(p) =135 solve for X 135- 2P /3 =X

Know how to balance equations ex: C8H18+O2 --> CO2+ H2O

first look at all elements except oxygen.. C8H18+O2--> 8CO2+9H20 = 9 oxygen+ 16 oxygen= 25 oxygens put the 25 next to the oxygen on the reactants side and multiple the rest of the coafficients by 2 2C8H18+ 25O2--> 16CO2+18H2O

Which of the following would the empirical formula of a compound that has 16 mole of oxygen 56 moles of nitrogen?

first to get the empirical formula simplify the number you get by the greatest common fact. in this case the greatest common factor is 8 N7O2

a volumetric flask weighs 185 g when empty and 380 grams when filed with "liquid A" (density 2 g*ml-1) if the flask is filled with 160 g of "liquid B", what is the density of liquid B

first we know density= mass/ volume liquid A mass is 380- 185= 205 2 g*ml-1 x 1/ 205 g x 160g/ 1=

hydrogen gas and nitrogen gas react to produce ammonia. How many liters of ammonia can be produced from 2 liters of hydrogen gas and 2 liters of nitrogen gas?

first write out the chemical reaction. N2+ 3H2--> 2NH3 2L H2 x 2 NH3/ 3H2 = 4/3 mol= 1.33 2 L N2 x 2NH3/1 N2 = 4mol the limited reagent is H2 gas and only 1.33 mol of ammonia can be produced. if they give you grams for each reactant you can determine the number of moles used to get the limited reagent. but for mole and litters you do mole to mole ratio reactant/ product

whats the charge when you gain and loose electrons

gain -1 loose +1

ground state vs. excited state

ground state= lowest energy excited state= not as would assign it but it doesnt break any rules.

2nd Quantum number= angular momentum

l tells us the shape and size. it is dependent on n. rule n-1=l ex. n=3 l= 0,1,2 l=0 s subshell l=1 p subshell l=2 d subshell l=3 f subshell

alpha decay

large nucleus wants to become more stable. To stabalize the nucleus the number of protons and neutrons is reduced by releasing alpha particles. alpha particle consists of 2 protons and 2 neutrons (similar to that of helium atom) so in this case the atomic number decreases by 2. number of neutrons decrease and number of protons decrease so this changes the nucleus mass number

molarity (M)

mole of solute/ L of solution

B- decay

more dangerous than alpha particle. have more energy and penetrating ability. B- decay when unstable, the number of neutrons is too high and neutrons are converted to protons and electrons. The atomic number is one greater than the radioactive parent nucleus the mass number remains the same. decrease number of neutrons increase number of protons

nuclear stability

neutrons and protons in the nucleus are held together by strong nuclear forces. (the most powerful force)

for any atom, the type of atom is determines by the?

number of protons

What are the charges for proton, electron and neutrons ?

proton +1 electron -1 neutron no charge

how many protons, neutrons and electrons are there in mercury-208 80

protons= 80 electrons=80 neutrons= 128

what is the symbol for protons and neutrons?

protons= Z neutrons= N neutron+ proton= atomic mass proton/ electron= atomic number

when you gain electron you go when you loose electrons you go

right on the periodic table left on the periodic table and the configuration changes upon that change.

Quantum number: 1st shell

s symbol n which tells us the size and energy of the electron. The greater the number of n the greater the energy and distance from the nucleus.

the mass defects of triton is about 0..009 amu. What is the nuclear binding energy?

since it is given in amu you can use the equation EB (in ev) =[m (in amu)] x 931.5 MeV 0.009 amu x 931.5=8.4 MeV

If a bohr atom absorbs photon:

the electron is excited

Bohr model of the atom

the greater distance of electrons from the nucleus the greater the energy of electrons

gamma decay

the nucleus in an excited energy state this is usually after the nucleus has undergone alpha or beta decay. the electron can relax to its ground state emmitting energy in the form of one or more photon. The released photons are called gamma photons they dont have mass or chargeand can penetrate matter most effictively. No change in atomic or mass number.

what is an isotope?

the same atoms with different number of neutron example beryllium-7 and beryllium-9 same atomic number but different mass number

half lifes

the shorter the half life= faster decay

fourth quantum number

the spins of electron. only 2 possible spins +1/2 or -1/2

Formula and molecular weight

the total mass of all elements in the formular ex C4H4N2 12(4)+1(4)+2(14)= 80

percent composition

try to get the formula into an empirical formula if its not empirical. %= element/ molecular weight

B+ decay

when the nucleus contains too few neutrons it converts the protons into neutrons and positrons (positively charged electron). The atomic number is 1 less than the resulting parent nucleus. increase number of neutrons decrease number of protons.

exception to the loosing electrons are transition metals

when transition metals loose electrons they loose them from the lower subshell (s) first