Early Content
What term is used to describe: Two distinct compounds with the same constituent elements have masses in a whole number ratio
Law of Multiple Proportions
What term is used to describe: Property that doesn’t depend on the amount of a substance.
Intensive Property
What term is used to describe: Energy stored in the structural units of substances
Chemical Energy
A student performs a reaction in a beaker. After mixing the chemicals, they feel the outside of the beaker, and it becomes warm. What type of reaction is most likely occurring?
A) Exothermic – the reaction releases heat to the surroundings
B) Endothermic – the reaction absorbs heat from the surroundings
C) Neither – the temperature change is unrelated to heat
D) Cannot tell from this information
Answer: Exothermic Reaction
What are the electron configuration for chromium?
1s22s22p63s23p63d54s1
or
[Ar]3d54s1
Student analyzes an unknown sample that appears uniform and boils at a constant temperature. When electricity is passed through its vapor, it always decomposes into two pure gases in the same mass ratio. Based on this information, the unknown sample is best classified as:
A. An element
B. A homogeneous mixture
C. A heterogeneous mixture
D. A compound
Answer D
Which of the following statements about energy and thermodynamic systems is correct?
A) An open system can exchange energy but not matter with its surroundings.
B) The enthalpy change of a reaction depends on the path taken to go from reactants to products.
C) Thermal energy is a form of kinetic energy associated with the random motion of particles.
D) Potential energy is always less than kinetic energy in chemical systems.
Answer C
Which of the following statements about electrons in atoms is correct
A) Electrons in the same orbital must have the same spin.
B) The principal quantum number nnn determines the energy and size of an electron’s orbital.
C) Electrons always occupy the highest energy orbitals first.
D) The magnetic quantum number mlm_lml determines the spin direction of an electron.
Answer B
Given the following data:
SrO(s) + CO2(g) ---> SrCO3(s)
ΔH = −234 kJ
2SrO(s) ---> 2Sr(s) + O2(g)
ΔH = +1,184,000 J
2SrCO3(s) ---> 2Sr(s) + 2C(s, gr) + 3O2(g)
ΔH = +2440 kJ
Find the ΔH of the following reaction:
C(s, gr) + O2(g) ---> CO2(g)
ΔH = 394 kJ
Which of the following sets of atomic numbers are possible?
a. n = 4; l = 4; ml = 4; ms = -1/2
b. n = 3; l = 3; ml = 0; ms = +-1/2
c. n = 1; l = 0; ml = -0; ms = -1/2
d. n = 4; l =2; ml = -3; ms = -1/2
e. n = 3; l = 0; ml = 0; ms = -1/2
f. n = 7; l = 2; ml = -1; ms = -1/2
g. n = 4; l = 0; ml = 1; ms = +3/2
Answer:c,e,f
A weather balloon filled with helium has a diameter of 3.00 ft. What is the mass in grams of the helium in the balloon at 21c and normal pressure? The density of helium under these conditions is 0.166 g/L.
66grams
A baker uses sodium hydrogen carbonate (baking soda) as the leavening agent in his recipe. The baking soda decomposes shown in the reaction bellow:
2NaHCO3 (s) → Na2CO3 (s) + H2O(l) + CO2 (g)
Calculate the volume in mL of CO2 that forms at 200°C and 0.975 atm per gram of NaHCO3 by each of the reaction processes.
0.237 L
The electron in a hydrogen atom undergoes a transition from an unknown state to the second excited state. The photon that is emitted from the hydrogen atom has a wavelength of 954 nm. What was the value of n for its state prior to the emission of the photon?
N = 7.98, about 8.
Uranium hexafluoride, UF6, is a white solid that sublimes (vaporizes without melting) at 57C under normal atmospheric pressure. The compound is used to separate uranium isotopes by effusion. What is the rms speed (in m/s) of a uranium hexafluoride molecule at 57C?
1.53 X 102 m/s
Order the following groups of elements from least to most electronegativity and smallest to largest radius.
Cl, O, F
O, C, N
S, Ge, Tl
1)
Electronegativity: Cl < O < F
Radius: F < O < Cl
2)
Electronegativity:C < N < O
Radius: O < N < C
3)
Electronegativity:Se < S < Cl
Radius: Cl < S < Se
4)
Electronegativity: Tl < Ge < S
Radius: S < Ge < Tl
Magnesium consists of three naturally occurring isotopes. The percent abundance of these isotopes is as follows: 24Mg (78.70%), 25Mg (10.13%), and 26Mg (11.7%). The average atomic mass of the three isotopes is 24.3050 amu. If the atomic mass of 25Mg is 24.98584 amu, and 26Mg is 25.98259 amu, calculate the actual atomic mass of 24Mg.
23.80 amu
An organic compound, A, containing only the elements carbon, hydrogen and oxygen was analyzed. A was found to contain 54.5% C and 9.1% H by mass, the remainder being oxygen. A 0.230 g sample of A, when vaporized, had a volume of 0.0785 dm3 at 95C and 102 kPa. Determine the Molecular formula of compound A.
C4H8O2
An experiment requires the preparation of a water bath at 40.0℃. The temperature of the cold tap water is 21.0℃, and the temperature of the hot tap water is 65.0℃. A student adds 90.0 g cold tap water to an insulated container at 21.0℃. What mass of hot tap water must be added to reach 40.0℃? The heat capacity for the container is 9.35 J/K, and the specific heat capacity for the water is 4.184 J/(g∙K).
70.1 g
An industrial process for manufacturing sulfuric acid, H2SO4, uses hydrogen sulfide, H2S, from the purification of natural gas. In the first step of this process, the hydrogen sulfide is burned to obtain sulfur dioxide, SO2.
2H2S(g) + 3O2(g) → 2H2O(l) + 2SO2(g); ΔH°= - 1124 kJ
The density of sulfur dioxide at 25C and 1.00 atm is 2.62 g/L, and the molar heat capacity is 30.2 J/(molC). In a reaction 1.00 L of SO2 is used at 25C and 1.00 atm. Suppose heat from this reaction is used to heat 1.00 L of SO2 from 25C and 1.00 atm to 500C for its use in the next step of the process. What percentage of the heat evolved is required for this?
2.55%
On periodic table draw out the trend for ionization energy, Radius size, Electronegativity.
Show me your work
For these two compounds please draw the lewis structure, Name the electron group, arrangement, and determine where it is polar or non-polar.
ClF5
SO32-
1) 6 , Octahedral, Square pyramidal, Polar covalent
2) 4 Tetrahedral, Trigonal pyramidal, Polar covalent
Explain why an ion with fewer shielding electrons typically has a higher ionization energy than its neutral atom.
ewer shielding electrons mean the outer electrons experience a stronger effective nuclear charge, so they are held more tightly by the nucleus. As a result, more energy is required to remove an electron, increasing the ionization energy.
3 Which of the following statements correctly describes the difference between the size of an atom and its corresponding ion?
A) Cations are larger than their neutral atoms because they gain electrons, increasing electron–electron repulsion.
B) Anions are smaller than their neutral atoms because they lose electrons, reducing shielding.
C) Cations are smaller than their neutral atoms because they lose electrons, decreasing electron–electron repulsion and allowing the nucleus to pull the remaining electrons closer.
D) Ionic size differs from atomic size because cations are smaller than neutral atoms and anions are larger than neutral atoms due to changes in electron–electron repulsion.
Correct answer D
What term is used to describe: the amount of energy required to remove an electron from an atom or ion in the gas phase.
Ionization energy
The cyanate ion (OCN-, C is central) is stable, while the fulminate ion (CNO-, N is central) is unstable. In fact, fulminate salts explode when struck; Hg(CNO)2 is used in blasting caps. Draw the Lewis structures (including any resonance forms and non-zero formal charges).
Why is the fulminate ion so unstable?
Fulimante has multiple nonzero charges,