ACS General Chemistry

What is the equation to find the Freezing point Depression? What is i and its two rules?
and what is the Kf(Constant) for water?
delta T (freezing point)=m(molality) * Kf * i
water Kf=1.86*C/molal
Van’t Hoff Factor (i) :how much particle dissolves
-ionic compounds separate in solution –depending how many ions they have
-molecular compounds don’t separate at all

Which metals in the Periodic table react vigorously with water @25*C and out of that group, which elements are the most reactive?
Group 1 Alkali Metals
Going down the group, the element is more reactive

Which elements make colored aqueous solutions
Transition Metals except Zn and Pb

Diamond is an example of what kind of solid?
Network Covalent

What is the equation for the First Law of thermodynamics?
Delta E= q + w

For a cubic unit cell, by what fraction do you multiply the number of atoms in the corners and the atoms in the middle of the vertical corners,
In a cube, there are 8 corners so you would multiply
8 * (1/8)= 1
In each border of the cube there is an atom in the middle,
there are 12 borders
12 * (1/4) = 3

How many atoms per unit cell do each have:
1. Hexagonal closed packed
2. Body centered cubic cell
3. Face centered cubic cell
a. 6
b. 4
c. 2

#2 A 10.00 g sample of a soluble barium salt is treated with an excess of sodium sulfate to precipitate 11.21 g BaSO4 (M = 233.4). Which barium salt is it?
(A) BaCl2 (M = 208.2)
(B) Ba(O2CH)2 (M = 227.3)
(C) Ba(NO3)2 (M = 261.3)
(D) BaBr2 (M = 297.1)
Steps:
1.) Write equation with “X” variable
2.) use precipitate mass to find moles
3.) Divide given salt mass(grams) over moles of the precipitate.

Answer: BaCl2

#6 Which aqueous solution exhibits the largest freezing point depression?
(A) 1.0 m KBr (C) 0.5 m MgCl2
(B) 0.75 m C6H12O6 (D) 0.25 m Ga2(SO4)3
Answer: KBr

When alpha particles were shot at a metal foil target to probe the structure of the atom most of the particles passed through without any deflection in path. Some particles were deflected at larger angles. This indicated to Rutherford that…….
(a) the metal foil was continuos matter
(b) the mass of the metal atoms was spread out evenly
(c) the atoms of the metal were mostly empty space
(d) the alpha particles had great penetrating power
Answer: The atoms of metal were mostly empty space.
(the large scattering angles of the alpha particles were only consistent in a small dense center. The rest of the atom had to be mostly empty space.

#8 Which metal reacts most vigorously with water at 25 °C? and why?
(A) Na (B) Mg (C) K (D) Ca
Answer: K
The further left an element is on the periodic table the more reactive it is with water.
*Group 1 alkali metals most reactive–and within that group, the lower the metal is in the column, the more reactive it is*

#9 Each of the following forms a colored aqueous solution EXCEPT
(A) Cr(NO3)3 (C) Cu(NO3)2
(B) Co(NO3)2 (D) Zn(NO3)2
Answer: Zn(NO3)2
*Transition metals make colored aqueous solutions except Pb 2+ and Zn 2+

#12 Which compound has the lowest normal boiling point?
Also, what are the first two things one should look at when doing this question?
(A) HF (B) HCl (C) HBr (D) HI
Answer: HCl
First: look for the type of intermolecular forces (the strongest force is Hydrogen bonding which is a H bonded to N,O,F)
Second: If there are same forces then you look at the molar mass—b/c the higher the molar mass, the higher the boiling point

#13 Which of the following would lead to an increase in the vapor pressure of a liquid?
What does volatile mean?
I. Increasing the temperature
II.adding a nonvolatile solute
Answer: only I
You can increase the vapor pressure by increasing temperature
Volatile means tendency of substance to vaporize, so nonvolatile refers to a substance that does not evaporate into a gas

#15 First of all what is enthalpy of vaporization and fusion?
How is the enthalpy of vaporization of a substance related to its enthalpy of fusion?
-enthalpy of vaporization is the amount of heat added to a liquid substance to transform it into gas
-enthalpy of fusion is the amount of heat added to a solid substance to transform it into a liquid

The enthalpy of vaporization is greater than the enthalpy of fusion

#20 The enthalpy change under standard conditions for which of the reactions below would be equal to the ∆H°f (enthalpy of formation) of NaOH(s)?
(A) Na(s) + H2O(l) –> NaOH(s) + 1/2 H2(g)
(B) Na(s) + 1/2 O2(g) + 1/2 H2(g) –> NaOH(s)
(C) Na(s) + 1/2 H2O2(l) –> NaOH(s)
(D) Na+(aq) + OH-(aq)–> NaOH(s)
Enthalpy of formation ∆H°f works with element in their standard/natural state

Answer:(B) Na(s) + 1/2 O2(g) + 1/2 H2(g) NaOH(s)

#22 Which of these reactions has ∆S° > 0?
(A) S (l) S (s, monoclinic)
(B) H2(g) + O2(g) –> H2O2(aq)
(C) H2(g) + 2 Ag+(aq)–> 2 H+(aq) + 2 Ag(s)
(D) PCl5(g)–> PCl3(g) + Cl2(g)
Entropy ∆S°can be viewed as a measure of randomness or disorder
∆S° increases from solid to liquid to gas phase

Answer: (D) PCl5(g) PCl3(g) + Cl2(g)

#24 The Ka of phosphoric acid, H3PO4, is 7.6 X 10^-3 at 25 °C. For the reaction

H3PO4(aq) –> H2PO4-(aq) + H+(aq)

∆H° = -14.2 kJ/mol. What is the Ka of H3PO4 at 60 °C?
(A)4.2 10^-3 (C) 8.5 10^-3
(B) 6.8 10^-3 (D) 1.8 10^-2

Use the Van’t Hoff Equation:

Answer: 4.2 10^-3

#25 For the reaction
5O2(g) + 4NH3(g) –> 4NO(g) + 6H2O(g)
if NH3 is being consumed at a rate of 0.50 M•s-1, at what rate is H2O being formed?
Answer: .75M/s

#27 In the reaction A B, a plot of 1/[A] vs. t is found to be linear. What is the reaction order in A?
Answer: Second order b/c 1/[A]

#28 The half-life of iodine-131 is 8.02 days. How long will it take for 80.% of the sample to decay?
(A) 2.6 days (C) 19 days
(B) 13 days (D) 32 days
Answer:19 days

#29 For the reaction
Cl2(aq) + 2 Br-(aq) –> Br2(aq) + 2 Cl-(aq)
which of the following could be used to monitor the rate?
I pH meter
II Spectrophotometer
Answer: Only II

#30 For a reversible exothermic reaction, what is the effect of increasing temperature on the equilibrium constant (Keq) and on the forward rate constant (kf)?
Answer: Keq decreases and kf increases

#32 What is the solubility of MgF2 (Ksp = 6.8 10-9) in pure water?
Answer: 1.2 10^-3 mol/L

#33 First, what is the formula for relating Kc and Kp?
What is the ratio Kc/Kp for the following reaction at 723 °C?
O2(g) + 3 UO2Cl2(g)—> U3O8(s) + 3 Cl2(g)
Answer: 81.8

#38 In a galvanic cell in which the following spontaneous reaction takes place, what process occurs at the cathode?
3 Ce4+(aq) + Cr(s)–> 3 Ce3+(aq) + Cr3+(aq)
Answer: Reduction of Ce4+(aq)

Because the cathode is the electrode at which reduction half-reactions occur

#39 How to figure out the total voltage;Which two half reactions when coupled will make a galvanic cell that will produce the largest voltage?
look at the options in test file
total voltage = (The positive voltage)- (negative voltage)
Answer: III and IV

#43 What is the value of the quantum number L for 5p orbital?
Answer: 1

#46 Which gas-phase atom has no unpaired electrons in its ground state?
(A) Li
(B) Be
(C) B
(D) C
Answer: Be

#47 Which halogen atom has the greatest electron affinity?
(A) F
(B) Cl
(C) Br
(D) I
Answer: Cl

Note: Fluorine has the greatest electron affinity, but there is an exception! Fluorine has a repulsion being so closes to its electrons, so Chlorine becomes the element with the highest electron affinity

#48 Which electronic transition in atomic hydrogen
corresponds to the emission of visible light? and why?
(A) n=5–> n=2
(C) n=3–> n=4
(B) n=1–> n=2
(D) n=3–> n=1
Answer: (A) n=5–> n=2

B/c the visible light is seen when a hydrogen electron drops from a higher energy level to n=2

#49 Which species are linear?
I. N(O)2 + II. (I)3 –
(A) I only
(C) Both I and II
(B) II only
(D) Neither I nor II
Answer: Both are linear
Both I and II

#50 The peroxymonosulfate anion, HS(O)5 – , has
(A) five sulfur-oxygen bonds and no oxygen-oxygen bonds.
(B) four sulfur-oxygen bonds and one oxygen-oxygen bond.
(C) three sulfur-oxygen bonds and two oxygen-oxygen bonds.
(D) one sulfur-oxygen bond and four oxygen-oxygen bonds.
Answer: (B)

#51 Which statement about bonding is correct?
(A) A sigma bond has cylindrical symmetry about the
bonding axis.
(B) A π bond is twice as strong as a sigma bond.
(C) A double bond consists of two π bonds.
(D) A π bond results from the sideways overlap of
hybridized orbitals.
Answer: (A) A sigma bond has cylindrical symmetry about the bonding axis.

#53 What is the bond order in NO?
Answer D 2.5

#56 What is the relationship between the two compounds below?
CH3CH2CH(CH3)CH2CH3
CH3CH2CH2CH(CH3)CH3
Answer: Structural isomers same identical chemical formula

#57 Which class of organic compounds does NOT contain oxygen?
(A) Alcohol (B) Amide (C) Amine (D) Ketone
amines don’t have oxygen –just nitrogen

#58 Compared to ionic compounds of similar molar mass, hydrocarbons typically have?
I. Higher water solubility
II. Higher melting points

(A) I only
(C) Both I and II
(B) II only
(D) Neither I nor II

Answer: Neither I nor II

Hydrocarbons don’t dissolve in water or have high melting points

Fill in:
For l :
s=
p=
d=
f=
What is ml?
For l:
s=0
p=1
d=2
f=3
ml= -l to l ; each orbital has 2 electron

Fill in with high or low in both columns– the conductivity and conductivity when fused
for these four bonding types:

Ionic
Covalent
Network Covalent
Metallic

Ionic low high
Covalent low low
Network Covalent low low
Metallic high high

Group 1 alkali metals the melting point _________as you go down the column
decrease

What is the formula for relating Kc and Kp
Kp= Kc (RT) ^delta n

delta n= moles of gas products- reactants

In a galvanic cell what type of reaction occurs at the cathode? How do you find the total voltage?
reduction
Find total voltage by subtracting positive voltage minus negative voltage

Know these things about pi and sigma bonds:
1.) a sigma has a _______ symmetry about the bonding axis
2.) a double bond consist of ____ sigma and ____ pi bond
3.) pi bonds are _______ than sigma bonds
4.) pi bonds result from sideways overlap of _____ orbitals
1.)cylindrical
2.) 1;1
3.) weaker
4.) p

How to find Bond Order? Write equation
– The more positive value, the more _____
Bond Order= 1/2(bonding e- – antibonding e-)
strong(stable)

Hydrocarbons don’t _______ in water and they have very _____ melting points
dissolve; low

#1 Calcium carbonate, CaCO3, decomposes upon heating to calcium oxide and carbon dioxide. What mass of solid calcium carbonate is required to produce 2.40 liters of carbon dioxide measured at STP?
Answer: 10.7 g
Use STP constant 0 C, 1 atm, 22.4L
Divide liters given over 22.4L

#2 Aspirin, C9H8O4, is prepared by the acetylation of salicylic acid, C7H6O3, according to the following equation:
C7H6O3 + (CH3CO)2O —> C9H8O4 + CH3COOH
If the yield of this reaction is 83%, what mass (in Kg) of salicylic
acid would be required to prepare 1.0 kg of aspirin?
Answer: .92kg

#4 A 5.73 g sample of a liquid hydrocarbon burned in excess oxygen produces 17.48 g CO2. What is the formula of the hydrocarbon?
(A) C5H12 (C) C6H10
(B) C6H6 (D) C6H12
Answer: C5H12

#5 A solution of 3.00 g of which substance, dissolved in 100 g H2O, has the highest boiling point?
(A) HOCH2CH(OH)CH2OH (M = 92.1)
(B) RbF (M = 104.5)
(C) AlCl3 (M = 133.3)
(D) TlNO3 (M = 390.4)
Answer: (C) AlCl3 (M = 133.3)
Use m(molality) = moles of solute(i)/kg of solvent
The highest molality has the highest boiling point

#7Each of the following substances dissolves exothermically in water EXCEPT
(A) NaOH(s). (C) CuSO4(s).
(B) NH4NO3(s). (D) H2SO4(l)
Strong bases and acids dissolve exothermically —also ionic compounds so,
Answer: B because NH4 is a weak acid

#8Which solid is most soluble in water at 25 oC?
(A) AgNO3 (B) CaCO3 (C) PbO (D) ZnS
Answer:AgNO3
because NO3 always dissolves

Example: A+ 2B <----> C+ 3D
Write the Kc formula for this reaction?
When can the Kc value change?

Does change in concentration to any of the products or reactions change the Kc value?

Kc is the equilibrium constant
Kc= [C]*[D]^3/ [A]*[B]^2

-The Kc value only changes with temperature change

-No–change in concentration does not change the Kc value

#13 Which of the following substances experience London Dispersion forces?
I. CH3CH3 II. CH3OH

A) I only
(C) Both I and II
(B) II only
(D) Neither I nor II

Answer: Both I and II

#14 Which of these pure substances has the highest normal boiling point?
(A) CH4
(B) NH3
(C) SiH4
(D) PH3
Answer: NH3

#15 A mixture of 0.50 mol of H2 gas and 1.3 mol of Ar gas is in a sealed container with a volume of 4.82 L. If the temperature of the mixture is 50.0 °C, what is the partial pressure of H2 in the sample?
Answer: 2.8 atm

#19 A system consists of a gas contained in a thin balloon. If the balloon deflates as the temperature of the gas changes from 90 oC to 25 oC, then
(A) Heat is transferred out of the system and work is done on the system.
(B) Heat is transferred out of the system and work is done by the system.
(C) Heat is transferred into the system and work is done on the system.
(D) Heat is transferred into the system and work is done by the system.
Answer:
Heat is transferred out of the system and work is done on the system

#20 The ∆Hf (enthalpy of formation) of MgO is -602 kJ•mol‒1. When 20.15 g MgO is decomposed at constant pressure according to the equation below, how much heat will be transferred?In order words for heat transferred is..?
2 MgO(s) –> 2 Mg(s) + O2(g)
This question is asking for heat absorbed.
When finding the heat transferred, it is always going to be positive because the heat of formation is negative.
Answer: 3.01×10^2 of heat absorbed

#21 What mass of ice at 0.0 oC must be added to 100. g H2O at 25.0 oC to cool it to 0.0 oC? The heat of fusion of ice is334J•g‒1.
Answer: 31.3 g

#22 on Sandra’s Exam
Answer: -455 kJ/mol

#23 Which halogen has the highest standard entropy S?
(A) F2(g)
(B) Cl2(g)
(C) Br2(l)
(D) I2(s)
Answer: CI2 (g)

#24 A chemical reaction has Keq = 1 10‒5 at 25 oC, and the value of Keq increases with increasing temperature. From these statements, what may one conclude?
A) ∆Ho>0and∆So>0
(B) ∆Ho<0and∆So<0 (C) ∆Ho<0and∆So>0
(D) ∆Ho > 0 and no conclusion may be drawn about the sign of delta S
Answer: ∆Ho > 0 and no conclusion may be drawn about the sign of delta S

#25 For the reaction
2 H2(g) + 2 NO(g) –> N2(g) + 2 H2O(g)
the rate law is rate = k[H2][NO]2. At a given temperature, what is the effect on the reaction rate if the concentration of H2 is doubled and the concentration of NO is halved?
(A) The reaction rate is halved.
(B) The reaction rate is unchanged.
(C) The reaction rate is doubled.
(D) The reaction rate increases eightfold.
Answer: The reaction rate is halved.

#28 Which of the following are reasons why reaction rates increase as temperature increases?
I. Collisions are more frequent between molecules at higher temperatures.
II. A greater fraction of collisions have sufficient energy to exceed Ea at higher temperatures.
III. Reactant concentrations are higher at higher temperatures.
(A) I only
(C) IandII
(B) II only
(D) I,II,andIII
Answer: C

#29 What is the effect of adding a catalyst on the rate of a reversible reaction in the forward and the reverse direction?
Answer: Both rates increase by the same factor.

#31 For the reaction
2 SO2(g) + O2(g) <-----> 2 SO3(g)
which statements are correct?
I. Kc = [SO2][O2]/[SO3]
II. Addition of O2(g) to the system at constant temperature and volume would decrease the value of Kc.
Answer: Neither I nor II

#37 What is the oxidation number of Re in Mg(ReO4)2?
Answer: +7

#41 Lithium ion batteries are now commonly used in rechargeable consumer electronic devices. The main reason lithium is used in these devices is because
Answer: lithium batteries achieve a greater amount of energy stored per unit mass than other common batteries.

#43 Which of the following sets of quantum numbers n, l, ml,ms correspond to a valence electron in a neutral atom of arsenic (As)?
(A) 3,0,0,+1/2 (C) 4,0,0,+1/2
(B) 3,2,1,-1/2 (D) 4,2,1,-1/2
Answer: 4,0,0,+1/2

#44 Which gas-phase atom has the largest radius?
(A) Na
(B) K
(C) Mg
(D) Ca
Answer: K

#46 Which element’s electronegativity is closest to that of S?
(A) O
(B) P
(C) Cl
(D) Se
Answer: Se

#47 Atomic nitrogen has a higher ionization energy than atomic oxygen. This is best explained by
(A) the lower electron-electron repulsion in nitrogen.
(B) the greater effective nuclear charge of nitrogen.
(C) the fact that the electron ionized in N is from the 2s subshell, while that ionized from O is from the 2p subshell.
(D) the fact that N has an odd number of electrons while O has an even number.
Answer: The lower electron-electron repulsion in nitrogen

#48 The energy required to break one mole of hydrogen- hydrogen bonds in H2 is 436 kJ. What is the longest wavelength of light (in nm) with sufficient energy to break a single hydrogen-hydrogen bond?
Answer: 274 nm

#49 In the Lewis structure for the selenite ion, SeO32-, how many lone pairs are around the central atom?
Answer: 1

#50 Removing an electron from molecular oxygen, O2, to form the dioxygenyl cation, O2+, causes what changes in the bond length and in the number of unpaired electrons?
Bond length: Increase or decrease
Number of unpaired electrons: increase or decrease
Answer: Decrease for both

b/c O2+ forms a triple bond

#51 Which of the following molecules has a dipole moment of zero?
(A) HCN
(C) SO2
(B) CH2Cl2
(D) CO2
Answer: CO2

#54 Which of the following are ionic compounds?
I. NH2NO2 II. NH4NO3
Answer: only II

What are the conditions for STP?
0 degrees celcius ; 1 atm ; 22.4L/mol

What are the conditions for SATP?
25 degrees celcius ; 100kPa ( 1 atm) ; 24.79 L/mol

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