Answer:
There are fifteen molecular orbitals in benzene filled with electrons.
Explanation:
Benzene is an aromatic compound. Let us consider the number of bonding molecular orbitals that should be present in the molecule;
There are 6 C-C σ bonds, these will occupy six bonding molecular orbitals filled with electrons.
There are 6 C-H σ bonds, these will occupy another six molecular orbitals filled with electrons
The are 3 C=C π bonds., these will occupy three bonding molecular pi orbitals.
All these bring the total number of bonding molecular orbitals filled with electrons to fifteen bonding molecular orbitals.
The element europium exists in nature as two isotopes: has a mass of u and has a mass of u. The average atomic mass of europium is u. Calculate the relative abundance of the two europium isotopes.
Answer:
Problem Details
The element europium exists in nature as two isotopes: 151Eu has a mass of 150.9196 amu, and 153Eu has a mass of 152.9209 amu. The average atomic mass of europium is 151.96 amu. Calculate the relative abundance of the two europium isotopes.
answer:
151Eu = 48%, 153Eu = 52%
1. Why is it not possible to resolve the compound CH3-NH-CH2-CH3 into a pair of enantiomers?
2. Which one of the following is not affected (or is least affected) by the lone pair of electrons on an amine's nitrogen?
a. solubility in alcohols and in water.
b. hydrogen-bond formation.
c. melting point.
d. dipole moment.
e. basicity.
3. Which of the following compounds is most basic?
a. cyclohexyl amine.
b. p-nitroaniline.
c. 2,6-dimethylaniline.
d. p-methoxyaniline.
d. aniline.
Answer:
1. In the compound, H3C-NH-CH2-CH3, there are no chiral centers present, chiral centers refer to the configuration in which carbon is attached with four different groups. In the molecules, as there are no chiral centers, therefore the molecule is optically inactive, that is, it will not demonstrate pair of an enantiomer is one of the essential characteristics of optically active compounds is the possession of enantiomeric pairs.
2. On the nitrogen of aniline, the lone pair of electrons can produce hydrogen bonds, play an essential function in basicity, play an essential role in dipole moment or polarity, and wit the increase in solubility there is an increase in the formation of the hydrogen bond, eventually increasing to boiling point. However, the melting point is not affected. As the melting point is the characteristic of the packing efficacy of a molecule and does not rely upon the anilinic nitrogen's lone pairs.
3. With the increase in the tendency to donate an electron, basicity increases. However, if the electron is taking part in resonance, the donation will not take place easily, and the compound will be the least basic. Apart from cyclohexyl amine, in all the other given compounds, the lone pair of nitrogen takes part in the process of delocalization or conjugation. Thus, cyclohexyl amine will be most basic as the lone pairs are easily available for donation.
Which of the following are characteristics of ionic
compounds?
Answer:
Ionic compounds have high melting points.
Ionic compounds are hard and brittle.
Ionic compounds dissociate into ions when dissolved in water.
Solutions of ionic compounds and melted ionic compounds conduct electricity, but solid materials do not.
Explanation:
The combination of a carbonyl group and a hydroxyl group on the same carbon atom is called a ________ group.
a. carbamate group
b. carbonate
c. carboxlate
d. carboxyl
Answer:
d. carboxyl
Explanation:
The presence of carbonyl group (>C=O)) and a hydroxyl group ( (−OH) on the same carbon atom is called a "carboxyl" group. A carboxyl group is represented as COOH and acts as the functional group part of carboxylic acids.
For example:
Formic acid or Methanoic acid (H-COOH) Butanoic acid (C3H7-COOH)Hence, the correct option is "d. carboxyl ".
What is Entropy?
A. The opposite of Enthalpy
B. The temperature at which a reaction is feasible.
C. A measure of disorder.
D. Free energy used for a reaction.
Answer:
C. A measure of disorder :)
How has the work of chemists affected the environment over the years?
Answer:
Chemistry is one of the causes for global warming, and in some cases it can even cause certain illnesses.
Answer:
Chemists have both hurt the environment and helped the environment by their actions.
Explanation:
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When NaOH is added to water, the (OH) = 0.04 M. What is the [H30*]?
What is the PH of the solution?
Answer:
[H₃O⁺] = 2.5 × 10⁻¹³ M
pH = 12.6
Explanation:
Step 1: Given data
Concentration of OH⁻: 0.04 M
Step 2: Calculate the concentration of H₃O⁺
Let's consider the self-ionization of water reaction.
2 H₂O(l) ⇄ OH⁻(aq) + H₃O⁺(aq)
The ionic product of water is:
Kw = [OH⁻] × [H₃O⁺] = 10⁻¹⁴
[H₃O⁺] = 10⁻¹⁴ / [OH⁻]
[H₃O⁺] = 10⁻¹⁴ / 0.04
[H₃O⁺] = 2.5 × 10⁻¹³ M
Step 3: Calculate the pH
The pH is:
pH = -log [H₃O⁺] = -log 2.5 × 10⁻¹³ = 12.6
Calculate the molality of a solution containing 141.5 g of glycine (NH2CH2COOH) dissolved in 4.456 kg of H2O
Answer:
0.423 m.
Explanation:
The following data were obtained from the question:
Mass of glycine (NH2CH2COOH) = 141.5 g
Mass of water = 4.456 kg
Molality =.?
Next, we shall determine the number of mole in 141.5 g of glycine (NH2CH2COOH.
This is illustrated below:
Mass of glycine (NH2CH2COOH) = 141.5 g
Molar mass of glycine (NH2CH2COOH) = 14 + (2x1) + 12 + (2x1) + 12 + 16 + 16 + 1 = 75 g/mol
Mole of glycine (NH2CH2COOH) =.?
Mole = mass /Molar mass
Mole of glycine (NH2CH2COOH) = 141.5/75
Mole of glycine (NH2CH2COOH) = 1.887 moles
Finally, we shall determine the molality of the solution as follow:
Molality is simply defined as the mole of solute per kilogram of water. Mathematically it is expressed as:
Molality = mole / mass (kg) of water
With the above formula, we can obtain the molality of the solution as follow:
Mole of glycine (NH2CH2COOH) = 1.887 moles
Mass of water = 4.456 kg
Molality =.?
Molality = mole /mass (kg) of water
Molality =1.887/4.456
Molality = 0.423 m
Therefore, the molality of the solution is 0.423 m
What is a chemical formula, and what does it tell you?
Explanation:
chemical formula tells you the specific elements included in the compound and the number of atoms of each. The letters in a chemical formula are the symbols for the specific elements. So for example, H means hydrogen.
Explanation:
A chemical formula is a way of presenting information about the chemical properties of atoms that contribute a particular chemical compound or molecule, using chemical elements.
The equilibrium constant K changes with changes in
the temperature.
The half-life of radium-226 is 1620 years. What percentage of a given amount of the radium will remain after 900 years
Answer:
68%
Explanation:
Since we need a percentage we can use any number we want for our initial value.
5(1/2)^900/1620 = 3.40
(3.40 / 5)*100 = 68%
To make sure lets use a different initial amount
1(1/2)^900/1620 = 0.68
(0.68/1) * 100 = 68%
To solve this question, we'll assume the initial amount of radium-226 to be 1.
Now, we shall proceed to obtaining the percentage of radium-226 that will after 900 years. This can be obtained as illustrated below:
Step 1Determination of the number of half-lives that has elapsed.
Half-life (t½) = 1620 years
Time (t) = 900 years
Number of half-lives (n) =?[tex]n = \frac{t}{t_{1/2}}\\\\n = \frac{900}{1620}\\\\n = \frac{5}{9}[/tex]
Step 2:Determination of the amount remaining
Initial amount (N₀) = 1
Number of half-lives (n) = 5/9
Amount remaining (N) =?[tex]N = \frac{N_{0} }{2^{n}}\\\\N = \frac{1}{2^{5/9}}[/tex]
N = 0.68Step 3Determination of the percentage remaining.
Initial amount (N₀) = 1
Amount remaining (N) = 0.68
Percentage remaining =?Percentage remaining = N/N₀ × 100
Percentage remaining = 0.68/1 × 100
Percentage remaining = 68%Therefore, the percentage amount of radium-226 that remains after 900 years is 68%
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All of the following are examples of allotropes of carbon EXCEPT Choose the one alternative that best completes the statement or answers the question. Choose the one alternative that best completes the statement or answers the question. diamond amorphous carbon quartz graphene all of the above
Answer:
quartz
Explanation:
The correct option would be quartz.
Allotropy is a phenomenon that describes the natural existence of the same element in different forms with different physical characteristics. Allotropes are therefore different forms of the same element.
Carbon as an element has several allotropes which include diamond, graphite, graphene, amorphous carbon, and fullerenes. Quartz is a crystalline solid that is composed of silicon dioxide and not carbon.
Hence, all the options are carbon allotropes except quartz.
You are a paleontology professor working at a dig site looking for fossils. You come across a deposit that is emitting radiation. Upon further testing you find that the sample is changing from carbon (atomic number 6) into nitrogen (atomic number 7) as radiation is emitted. What type of radiation is it?
Answer:
β particles
Explanation:
The most common radioactive isotope of carbon is C-13.
The unbalanced nuclear equation is
[tex]\rm _{6}^{13}C \longrightarrow \, ? + \, _{7}^{13N}[/tex]
Let's write the question mark as a nuclear symbol.
[tex]\rm _{6}^{13}C} \longrightarrow \, _{Z}^{A}X+ \, _{7}^{13}N[/tex]
The main point to remember in balancing nuclear equations is that the sums of the superscripts and the subscripts must be the same on each side of the equation.
Then
13 = A + 13, so A = 13 - 13 = 0, and
6 = Z + 7, so Z = 6 - 7 = -1
Then, your nuclear equation becomes
[tex]\rm _{6}^{13}C \longrightarrow \, _{-1}^{0}M + \, _{7}^{13}N[/tex]
The particle with "zero" mass and a charge of -1 is an electron, so the balanced nuclear equation is
[tex]\rm _{6}^{13}C \longrightarrow \, _{-1}^{0}e + \, _{7}^{13}N[/tex]
The radiation consists of β particles (electrons)
Answer:
I think think that the one above me is beta radiation
Explanation:
Which of the following has the greatest effect on colligative properties?
A. Calcium chloride (CaCl2)
B. Sodium chloride (NaCl)
C. Aluminum Nitrate (Al(NO3)3)
D. Epsom salt (MgSO4)
Answer:
C. Aluminum Nitrate (Al(NO3)3)
Explanation:
This is because, when Aluminium nitrate dissolves in water, it dissociates to form four ions ( one aluminium ion and three nitrate ions ). Since colligative property depends on number of particles or ions present ( roult's law ), this will create much effect.
[tex]Al(NO _{3} )_{3(aq)} → Al {}^{3 + } _{(aq)} + 3NO {}^{ - } _{(aq)}[/tex]
Answer:
aluminum nitrate (Al(NO3)3)
it has the greatest effect on collimation properties .
Explanation:
(c) is correct option
Using these metal ion/metal standard reduction potentials Cd2+(aq)|Cd(s) Zn2+(aq)|Zn(s) Ni2+(aq)|Ni(s) Cu2+(aq)/Cu(s) -0.40 V -0.76 V ‑0.25 V +0.34 V Calculate the standard cell potential for the cell whose reaction is Ni2+(aq) + Zn(s) →Zn2+(aq)+ Ni(s)
Answer: The standard cell potential for the cell is +0.51 V
Explanation:
Given : [tex]E^0_{Ni^{2+}/Ni}=-0.25V[/tex]
[tex]E^0_{Zn^{2+}/Zn}=-0.76V[/tex]
The given reaction is:
[tex]Ni^{2+}(aq)+Zn(s)\rightarrow Zn^{2+}(aq)+Ni(s)[/tex]
As nickel is undergoing reduction, it acts as cathode and Zinc is undergoing oxidation, so it acts as anode.
[tex]E^0_{cell}=E^0_{cathode}-E^0_{anode}[/tex]
where both [tex]E^0[/tex] are standard reduction potentials.
Thus putting the values we get:
[tex]E^0_{cell}=-0.25-(-0.76)[/tex]
[tex]E^0_{cell}=0.51V[/tex]
Thus the standard cell potential for the cell is +0.51 V
Read the article. Use your understanding to answer the questions that follow. What type of source is this article? primary or secondary and how do you know
Answer: C
Explanation:
The article was sourced from the Oak National Laboratory
Which reasons did you include in your response? Check all of the boxes that apply.
1. The article does not present original research.
and
3. The article has references to primary sources.
Answer:
C
Explanation:
Which reasons did you include in your response? Check all of the boxes that apply.
The article does not present original research.
The article summarizes other research.
The article has references to primary sources.
Briefly describe how you can use spectra as evidence of nuclear fusion in stars.
Spectra can be used as an evidence that nuclear fusion occurs in the star through the ability of the elements generated to absorb light at specific wavelength.
The internal part of the star is made up of hydrogen gas, with a little helium.
The helium atom is formed through the nuclear fusion reaction that occurs in the core of the star.
Nuclear fusion reaction involves the combination of two or more atoms which leads to the formation of a new atom with the emission of great energy. This reaction leads to formation of helium elements in the core of the stars.
To detect if nuclear fusion reaction is occurring in the stars, a spectrum is used.
Because each element emits or absorbs light only at specific wavelengths, the chemical composition of stars can be determined using a spectrum.
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Consider the bond dissociation energies listed below in kcal/mol. CH3-Br 70 CH3CH2-Br 68 (CH3)2CH-Br 68 (CH3)3C-Br 65 These data show that the carbon-bromine bond is weakest when bromine is bound to a __________.
Answer:
The answer is "Tertiary carbon".
Explanation:
Accent to the results, the carbon-bromine bond is weak, whenever, the bromine is connected to tertiary carbon so, bonding energy is separation for methyl-carbon, which is connected to the bromine = 70 kcal/mol and for the primary energy to the secondary energy is= 68 kcal/mol, and for tertiary CO2 = 65 kcal/mol.
The stronger the energy dissociating connection and the weaker, its power dissociation connection and its weaker bond becomes connecting with a tertiary carbon, that's why "Tertiary carbon" is the correct answer.
In a fixed cylinder are 3moles of oxygen gas at 300Kelvin and 1.25atm. What is the volume of the container?
Answer:
The volume of the container is 59.112 L
Explanation:
Given that,
Number of moles of Oxygen, n = 3
Temperature of the gas, T = 300 K
Pressure of the gas, P = 1.25 atm
We need to find the volume of the container. For a gas, we know that,
PV = nRT
V is volume
R is gas constant, R = 0.0821 atm-L/mol-K
So,
[tex]V=\dfrac{nRT}{P}\\\\V=\dfrac{3\ mol\times 0.0821\ L-atm/mol-K \times 300\ K}{1.25\ atm}\\\\V=59.112\ L[/tex]
So, the volume of the container is 59.112 L
whats the ph for a solution poh4 9.78 concentration of solution
Answer:
4.22
Explanation:
According to the question, the pOH of the solution is 9.78. You may recall that pOH is the hydroxide concentration of a solution.
Also pOH = -log[OH^-]. Hence the pOH is obtained from the hydroxide ion concentration.
Finally, pH + pOH =14
Hence;
pH = 14-pOH
pH= 14-9.78 = 4.22
pH= 4.22
A graph of gas pressure versus the number of particles in a container is a straight line. Which other relationship will have a similar graph?
Answer:
volume versus temperature, because they are also directly proportional.
Explanation:
Just took the test!
what is ammonium nitrate
Answer:
Ammonium nitrate is a chemical compound with the chemical formula NH₄NO₃. It is a white crystalline solid consisting of ions of ammonium and nitrate.
how do elasticity ang flexibility differ?
Answer:
the object will regain its original form as soon as the deforming force is removed. ... Flexibility means the object is just easily deformed, and will stay that way.
Explanation:
You wish to construct a galvanic cell with the anode consisting of a Ni electrode in a 1.0 M Ni(NO3)2 solution. What would be the highest standard cell potential if used as the cathode in this galvanic cell?
Answer:
Au^3+(aq) +3e ------> Au(s). 1.50 V
Explanation:
When we construct the galvanic cell, our intention is to produce energy by spontaneous electrochemical reactions. In order to have a spontaneous electrochemical reaction, E°cell must be positive. The more positive the value of E°cell, the more spontaneous the reaction is.
E°cell= E°cathode - E°anode
If E°cathode= 1.50 V
E°anode= -0.25 V
E°cell= 1.50 -(-0.25)
E°cell= 1.75 V
Hence the process; Au^3+(aq) +3e ------> Au(s) yields the highest standard cell potential
A student puts a glass of water in the freezer. Later, he notices ice forming on the surface of the water. Which property of water best explains why ice forms on its surface? A. It is made of polar molecules. B. It has low surface tension. C. It has weak adhesion. D. It is densest as a solid.
ℯ ℴ ℴ ℴℯℯ
it has a weak adhesion
Calculate the pH of a solution that is 0.210 M in nitrous acid (HNO2) and 0.290 M in potassium nitrite (KNO2). The acid dissociation constant of nitrous acid is 4.50 × 10-4.
Answer:
pH = 3.49
Explanation:
We have a buffer system formed by a weak acid (HNO₂) and its conjugate base (NO₂⁻ coming from KNO₂). We can calculate the pH of a buffer ssytem using the Henderson-Hasselbach equation.
pH = pKa + log [base] / [acid]
pH = -log Ka + log [NO₂⁻] / [HNO₂]
pH = -log 4.50 × 10⁻⁴ + log 0.290 M / 0.210 M
pH = 3.49
The pH of the solution containing 0.210 M nitrous acid (HNO₂) and 0.290 M potassium nitrite (KNO₂) is 3.49
We'll begin by calculating the the pKa of acid. This can be obtained as follow:
Acid dissociation constant (Ka) = 4.50×10¯⁴
pKa =?pKa = –Log Ka
pKa = –Log 4.50×10¯⁴
pKa = 3.35Finally, we shall determine the pH of the solution.pKa = 3.35
Concentration of HNO₂, [HNO₂] = 0.210 M
Concentration of KNO₂, [KNO₂] = 0.290 M
pH =?The pH of the solution can obtain by using the Henderson-Hasselbach equation as illustrated below:
pH = pKa + log [base] / [acid]pH = pKa+ log [NO₂⁻] / [HNO₂]
pH = 3.35 + log (0.290 / 0.210)
pH = 3.49Thus, the pH of the solution is 3.49
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In the Lewis structure of AB4 where B is more electronegative than A. Both are main group elements where A has 8 valence electrons and each B has 7 valence electrons.
Required:
a. What is the total number of valence electrons?
b. How many lone pairs are in the molecule?
Answer:
1. 36
2. Two
Explanation:
The Lewis structure shows the valence electrons present in a compound. Usually the valence electrons are shown as dot structures around the symbol of the elements involved in the compound.
For a compound AB4 where B is more electronegative than A and A has 8 electrons in its valence shell, there will be thirty six valence electrons on the outermost shell of the molecule.
There are six electron pair domains present in the molecule, four bond pairs and two lone pairs. The molecule is in a square planar geometry.
Answer: a- 36 valence electrons
b- 14 lone pairs
Explanation:
Valence is equal to A + 4B = 8 + 4(7)
With 4 bonds between A and the 4 B, that is 36 valence minus 8 electrons in those pairs = 28. 28 is 14 lone pairs.
Determine whether each phrase describes carboxylic acids or esters.a. Do not form hydrogen bonds amongst themselves and have higher vapor pressureb. Form hydrogen bonds amongst themselves and have lower vapor pressurec. Notable for their pleasant fragrancesd. Their reactions with base are kn. own as saponificationse. Usually have a sour odorf. Their reactions with base are known as neutralizations
Explanation:
a. Esters
b. Carboxylic acids
c. Esters (ethyl hexanoate smells like pineapple)
d. Carboxylic acids (produces a carboxylic salt)
For the given phrases the following description is better.
a. Esters
b. Carboxylic acids
c. Esters (ethyl hexanoate smells like pineapple)
d. Carboxylic acids (produces a carboxylic salt)
Esters and carboxylic acids:An ester is a synthetic compound got from a corrosive in which somewhere around one - OH hydroxyl bunch is supplanted by an - O-alkyl (alkoxy) bunch, as in the replacement response of a carboxylic acid and a liquor.
Carboxylic acid is any of a class of natural mixtures in which a carbon (C) particle is clung to an oxygen (O) molecule by a twofold bond and to a hydroxyl bunch (―OH) by a solitary bond.
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at 89 ∘C∘C , where [Fe2+]=[Fe2+]= 3.60 MM and [Mg2+]=[Mg2+]= 0.310 MM . Part A What is the value for the reaction quotient, QQQ, for the cell?
Answer:
8.6×10^-2
Explanation:
The reaction is;
Mg(s) + Fe^2+(aq) -----> Mg^2+(aq) + Fe(s)
This implies that;
Q = [Mg^2+]/[Fe^2+]
But;
[Fe2+]= 3.60 M
[Mg2+]= 0.310 M
Q= [0.310 M]/[3.60 M]
Q= 0.086
Q= 8.6×10^-2
An ice cube at 0.00C with a mass of 8.32g is placed Into 55g of water, initially at 25C. If no heat is lost to the surroundings, what is the final temperature of the entire water sample after all the ice is melted (answer must be in 3 sig figs)
Answer:
The final temperature of the entire water sample after all the ice is melted, is 12,9°C. We should realize that if there is no loss of heat in our system, the sum of lost or gained heat is 0. It is logical to say that the temperature has decreased because the ice gave the water "heat" and cooled it
Thats all i know