Which of the following statements about semi-empirical methods are true?
a. It combines a theoretically sound model of bonding with some experimentally determined parameters.
b. It is faster to calculate than ab initio methods.
c. It can determine precisely both the location and the energy of bonding electrons.
d. It treats bonds simply as springs.
Answer:
a
Explanation:
The correct statement about semi-empirical methods is
It combines a theoretically sound model of bonding with some experimentally determined parameters.
These methods are typically referred to by acronyms which encode some of the underlying theoretical assumptions.
what information is given on a material safety data sheet?
Answer:
The MSDS lists the hazardous ingredients of a product, its physical and chemical characteristics (e.g. flammability, explosive properties), its effect on human health, the chemicals with which it can adversely react, handling precautions, the types of measures that can be used to control exposure, emergency and first
Explanation:
just put:- it lists the hazardous ingredints- its effect on human health- how the chemicals react to it- how to hanle- how to control exposuresHOPE THIS HELPS!BRAINLIEST?Please answer this. List the three most abundant minerals in this bottle of mineral water.
g In science, we like to develop explanations that we can use to predict the outcome of events and phenomena. Try to develop an explanation that tells how much NaOH needs to be added to a beaker of HCl to cause the color to change. Your explanation can be something like: The color change will occur when [some amount] of NaOH is added because the color change occurs when [some condition]. The goal for your explanation is that it describes the outcome of this example, but can also be used to predict the outcome of other examples of this phenomenon. Here's an example explanation: The color of the solution will change when 40 ml of NaOH is added to a beaker of HCl because the color always changes when 40ml of base is added. Although this explanation works for this example, it probably won't work in examples where the flask contains a different amount of HCl, such as 30ml. Try to make an explanation that accurately predicts the outcome of other versions of this phenomenon.
Answer:
See explanation
Explanation:
A titration involves the addition of a titrant to an analyte solution. It is a method of volumetric analysis.
When a particular volume of titrant is added, the colour changes to signal the end point of the reaction.
The point at which the colour changes is called the equivalence point. This is the point at which the amount of titrant added is just enough to completely neutralize the analyte solution.
Hence the volume NaOH that needs to be added to the beaker containing HCl to cause a colour change is the volume of NaOH that is just enough to completely neutralize the HCl solution.
Difference between Aluminum and Duralumin
Oxidation of a dithiol such as 2,5-hexanedithiol forms a six-membered ring containing a disulfide group as part of the ring. Draw the structure of this cyclic disulfide (Hint: Draw the starting compound in line structure format first).
Answer:
See picture below
Explanation:
In general terms, oxidation of thiol are rather different than oxidations with alcohols.
A dithiol is a molecule that has two thiols in an organic compound. In the case of the 2,5 hexanedithiol, we have the thiols in the carbon 2 and carbon 5.
When oxidation of thiols occurs, and depending of the number of thiols in the molecule, the final compound will have a sulfide group.
This is because the oxydation makes that the hydrogen atom of the sulfur is substracted. So, in the case of the dithiols, we have that both hydrogen atoms are substracted and then, they are available to join. Therefore, As the thiols are in the same molecule, it will occur a self condensation reaction.
The picture below will show the final product.
Hope this helps
Oxidation of a dithiol such as 2,5-hexanedithiol forms a six-membered ring containing a disulfide group as part of the ring. The structure of the cyclic disulfide that is 2,5-hexanedione is shown below.
Oxidation is a chemical reaction that involves the loss of electrons by a molecule, atom, or ion. This process results in an increase in the oxidation state of the species undergoing oxidation.
The oxidation of 2,5-hexanedithiol is a chemical reaction in which the thiol [tex]\rm (-SH)[/tex] groups of the molecule are converted into disulfide[tex]\rm (-S-S-)[/tex] bonds, resulting in the formation of 2,5-hexanedione. This reaction usually requires an oxidizing agent, such as hydrogen peroxide or nitric acid.Therefore, the structure of cyclic disulfide(2,5-hexanedione) is shown below.
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Two reactants that are used in the process of cellular respiration are
glucose and water
oxygen and water.
water and carbon dioxide.
carbon dioxide and oxygen.
Answer:
The answer is actually glucose and oxygen
Why is it important to know gas properties at STP?
Answer:
STP values are most often cited for gases because their characteristics change dramatically with temperature and pressure. One common definition of STP is a temperature of 273 K (0° Celsius or 32° Fahrenheit) and the standard pressure of 1 atm. Under these conditions, one mole of a gas occupies 22.4 L.
How is a magnetic field produced?
O when an electromagnetic field interacts with a magnet
O when a current runs through a conductor
O when an object has an electric charge
O when electrons move through a circuit
Answer:
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. ... Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin.
Answer: when an electromagnetic field interacts with a magnet
Explanation:
Observation of balloon rub with cloth?
Answer:
When rubbing a balloon with a wool cloth, it puts negative charges on the balloon. Negative charges attract to positive charges. ... When both balloons are rubbed with the wool cloth, the both receive negative charges, so they will repel each other.
Given the following steps for a mechanism:
Step 1: O3 + NO = NO2 + O2 (slow)
Step 2: NO2 + O = NO + O2(fast)
Define mechanism.
Explanation:
Prokaryotes have the advantages associated with greater simplicity, including more rapid reproduction, rapid mutation and adaptation to new environments, and more diverse metabolic systems. They also possess an ability to pass on adaptive genes to other bacteria in the form of plasmids.
Which formulas represent ionic compounds and which represent covalent compounds?
Covalent compound:
CsF
Na o
CHN
PCI,
Cao
CHO
NH
WO
lonic compound:
Cs
CdBr,
N
SOS
Answer:
See answer below
Explanation:
This is pretty easy to solve. First you need to understand that an ionic compound is usually formed between a metal and a non metal. This usually happens between elements from group 1 through group 10 or 11 of the periodic table. A covalent compound is always given in non metal elements from the periodic table, and it's usually the elements from group 13 through group 17.
Some compounds there are missing some atoms, but I manage to find this question and saw the atoms missing, so, in my answer you will see the corrected compound. so don't be surprised.
According to what I state above, then the covalent compounds are:
C₆H₅N
PCl₃
C₂H₄O
NH₃
N₂
SO₄²⁻
The ionic compounds are:
CaO
CdBr₂
WO₂
Na₂O
CsF
Hope this helps
Write the balanced equation and draw the particulate representation of the following chemical reaction: sodium metal reacts with chlorine gas to produce sodium chloride.
Draw the complete decomposition of 4 molecules of hydrogen peroxide (H2O2) into water and oxygen gas.
Complete the particulate representation of the combustion of methane (CH4) with oxygen to form carbon dioxide (CO2) and water.
Answer:
2Na + Cl2 ------> 2NaCl
4H2O2 --------> 4H2O + 2O2
CH4 + 2O2 -------> CO2 + 2H2O
Explanation:
The balanced chemical equations for the given chemical reactions are given serially i) 2 Na+Cl₂[tex]\rightarrow[/tex] 2 NaCl ii) 4 H₂O₂[tex]\rightarrow[/tex] 4 H₂O + 2 O₂ iii)CH₄ +2 O₂[tex]\rightarrow[/tex]CO₂ +2 H₂O
What is chemical equation ?Chemical equation is a symbolic representation of a chemical reaction which is written in the form of symbols and chemical formulas.The reactants are present on the left hand side while the products are present on the right hand side.
A plus sign is present between reactants and products if they are more than one in any case and an arrow is present pointing towards the product side which indicates the direction of the reaction .There are coefficients present next to the chemical symbols and formulas .
The first chemical equation was put forth by Jean Beguin in 1615.By making use of chemical equations the direction of reaction ,state of reactants and products can be stated. In the chemical equations even the temperature to be maintained and catalyst can be mentioned.
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if a gas at 300k occupies 3.60 liters at a pressure of 1.00 atm, what will be it’s new pressure if the volume is compressed to 2.0 liters at a temperature of 450K?
Answer: The new pressure if the volume is compressed to 2.0 liters at a temperature of 450K is 2.7 atm
Explanation:
The combined gas equation is,
[tex]\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}[/tex]
where,
[tex]P_1[/tex] = initial pressure of gas = 1.00 atm
[tex]P_2[/tex] = final pressure of gas = ?
[tex]V_1[/tex] = initial volume of gas = 3.60 L
[tex]V_2[/tex] = final volume of gas = 2.0 L
[tex]T_1[/tex] = initial temperature of gas = [tex]300K[/tex]
[tex]T_2[/tex] = final temperature of gas = [tex]450K[/tex]
Now put all the given values in the above equation, we get:
[tex]\frac{1.00\times 3.60}{300}=\frac{P_2\times 2.0}{450}[/tex]
[tex]P_2=2.7atm[/tex]
The new pressure is 2.7 atm
Over an interval of 2.0 s the average rate of change of the concentration of C was measured to be 0.0540 M/s. What is the final concentration of A at the end of this same interval if its concentration was initially 2.000 M
Answer:
Explanation:
the average rate of change of the concentration =
( initial concentration - final concentration ) / time
Initial concentration = 2.000 M
the average rate of change of the concentration = .0540 M/s
time = 2 s
Putting the values
.0540 = (2.000 - X ) / 2
0.108 = 2.000 - X
X = 1.892 M .
Final concentration = 1.892 M .
what is the atomic number for meitnerium
Answer:
"Meitnerium/Atomic number""109"Explanation:
Meitnerium, the topic of this podcast, with the symbol Mt and atomic number 109, sits in the middle of this band in group 9 underneath cobalt, rhodium and iridium.
Hope this is fine for you7. A number of reactions that take place on the surfaces of catalysts are zero order in the reactant. One example is the decomposition of ammonia on hot tungsten. In one experiment, the partial pressure of ammonia decreased from 21 kPa to 10 kPa in 770 s. (a) What is the rate constant for the zero-order reaction
Answer:
14.29 Pa/s
Explanation:
Given that, for a zero order reaction;
[A] = [A]o - kt
[A] = pressure at time =t
[A]o = initial pressure
k = rate constant
t = time taken
10 * 10^3 Pa = 21 * 10^3 Pa - 770k
10 * 10^3 Pa - 21 * 10^3 Pa = -770k
-11* 10^3 = -770k
k = -11* 10^3/-770
k = 14.29 Pa/s
What is the correct name for Hg(NO3)2?
Mercury (I) nitrate
Mercury (II) nitrate
Mercury nitroxide
Mercury dinitride
Answer: Hg(NO3)2 = Mercury (II) nitrate
The other answer is wrong. Mercury (I) nitrate is Hg2(NO3)2.
i need help with this science pls
Answer:
1)40n
2)25n
Explanation:
subtract the numbers if its on the opposite sides and add if its on same side
thank u hope it helps
Sarah was walking and picked up a rock that she thought looked interesting. The rock appeared to have layering, and contain fragments of shells and bones. What is the correct classification of the rock Sarah picked up?
Igneous
Metamorphic
Sedimentary
Volcanic
Mason notices that his boat sinks lower in the water in a freshwater lake than in the ocean. what could explain this
Answer:
Mason notices that his boat sinks lower into the water in a freshwater lake than in the ocean. What could explain this?
Explanation:
The freshwater has less density then the ocean!
cos(A)+cos(2A)+cos(3A)=0 is not an identity
Answer:
this is the required answer look it once
Which has more calories: table sugar or aspartame?
Hello there!
Aspartame has 4 kilocalories of energy per gram and table sugar has 3.9 kilocalories. They are pretty much same but aspartame is 200 times sweeter than sucrose so probably would be aspartame that has more calories.
A student increases the temperature of a 200 cm balloon from 60°C to 120°C.
What will the new volume of the balloon be?
A)100cm^3
B)200cm^3
C)263cm^3
D)400cm^3
Answer:
236 cubic cm
Explanation:
We are given that
Initial volume, V1=200 cubic centimeter
Initial temperature, T1=60 degree Celsius=60+273=333 K
Final temperature, T2=120 degree Celsius=120+273=393 K
Kelvin temperature=Celsius temperature+273
We have to find the new volume of the balloon.
We know that
Charles's law
[tex]\frac{V_1}{T_1}=\frac{V_2}{T_2}[/tex]
Using the formula
[tex]\frac{200}{333}=\frac{V_2}{393}[/tex]
[tex]V_2=\frac{200\times 393}{333}[/tex]
[tex]V_2=236cm^3[/tex]
Hence, the new volume of the balloon will be 236 cubic cm.
Rearrange each jumbled letters
1. EMITNGL IPTNO
2. USLTBIAOMNI
3. RZFENIGE OTPNI
4. ENSODIOTIP
5. ETHA
Answer:
1. MELTING POINT
2. SUBLIMATION
3. FREEZING POINT
4. DEPOSITION
5. HEAT
Explanation:
What is a net ionic equation?
A. An equation that shows all substances as compounds
B. An equation that is balanced on both sides
C. An equation showing only what is involved in the reaction
D. An equation that shows all dissolved compounds as ions
Answer:
I think it will option D hope it helps
Describe the breeding place, type of fertilization, and development of the
embryo of the selected animals listed in the table below.
Table 2. Reproduction and Development in Selected Animals
help help
patulong po
Answer:
Breeding is defined as the process of mating or sexual reproduction between two organism to produce an offspring.
Fertilization is the process in which eggs and sperm fuse together to form a zygote.
After fertilization, embryo development takes place inside females body and form a whole new organism or plant.
In the given examples:
Milkfish:
Breeding place land or water: water
Fertilization external or internal: internal
Development of embryo (outside or inside) the female's body: outside
Cat:
Breeding place land or water: Land
Fertilization external or internal: internal
Development of embryo (outside or inside) the female's body: inside
Frog:
Breeding place land or water: Land
Fertilization external or internal: inside
Development of embryo (outside or inside) the female's body: outside
Duck:
Breeding place land or water: Land
Fertilization external or internal: Internal
Development of embryo (outside or inside) the female's body: Outside
Cow:
Breeding place land or water: Land
Fertilization external or internal: internal
Development of embryo (outside or inside) the female's body: inside
Liquid hexane CH3CH24CH3 will react with gaseous oxygen O2 to produce gaseous carbon dioxide CO2 and gaseous water H2O. Suppose 4.3 g of hexane is mixed with 25.8 g of oxygen. Calculate the maximum mass of carbon dioxide that could be produced by the chemical reaction. Round your answer to 2 significant digits.
Answer:
13g of CO₂ is the maximum amount that could be produced
Explanation:
The reaction of hexane with oxygen is:
C₆H₁₄ + 19/2O₂ → 6CO₂ + 7H₂O
Where 19/2 moles of oxygen react per mole of C₆H₁₄
To solve this question we need to find theoretical yield finding limiting reactant :
Moles C₆H₁₄:
4.3g C₆H₁₄ * (1mol / 86.18g) = 0.0499 moles
Moles O₂:
25.8g * (1mol / 32g) = 0.806 moles
For a complete reaction of 0.0499 moles of C₆H₁₄ are needed:
0.0499 moles of C₆H₁₄ * (19/2 mol O₂ / 1mol C₆H₁₄) = 0.474 moles of O₂.
As there are 0.806 moles, O₂ is in excess and C₆H₁₄ is limiting reactant
In theoretical yield, the moles of hexane added = 6Moles of CO₂ produced. Moles of CO₂ are:
0.0499 moles C₆H₁₄ * (6mol CO₂ / 1mol C₆H₁₄) = 0.299 moles CO₂
In grams:
0.299 moles CO₂ * (44.01g / mol) = 13g CO₂
13g of CO₂ is the maximum amount that could be produced
Which is the correct molar mass for the compound h2SO4
Explanation: just add the atomic masses on the periodic table together for each atom.
Answer:Sulfuric acid
Explanation:because I said so
what is a arieal animals?