HELP! 30 POINTS!!
2. Which of the following statements are true about a strong base and a weak base at a pH of 11?
HCl will not bring the pH of either solution to pH 7.
Both bases require the same amount of HCl to reach pH 7 because they are both
at the same initial pH.
The weak base will require less HCl to bring the pH to 7 than the strong base. The strong base will require less HCl to bring the pH to 7 than the weak base.
the answer is definatly A
The half-life of the radioactive element unobtanium dash 53 is 20 seconds. if 32 grams of unobtanium dash 53 are initially present, how many grams are present after 20 seconds? 40 seconds? 60 seconds? 80 seconds? 100 seconds?
Answer: After 20 seconds, 16 grams of unobtanium will be present, after 40 seconds, 8 grams of unobtanium will be present after 60 seconds, 4 grams of unobtanium will be present, after 80 seconds, 2 grams of unobtanium will be present and after 100 seconds, 1 grams of unobtanium will be present.
Explanation: Half life is the time in which half of the reaction is completed. Thus the half of the substance will be decomposed and half of it will remain.
Amount of the substance left after n half lives will be=[tex]\frac{A}{2^n}[/tex]
where A= initial amount of substance
n=no of half lives=[tex]\frac{\text{given time}}{\text{half life}}[/tex]
a) t= 20 seconds
no of half lives=[tex]\frac{20}{20}=1[/tex]
amount of the substance left after 1 half life will be=[tex]\frac{32}{2^1}[/tex]=16 g.
b) t= 40 seconds
no of half lives=[tex]\frac{40}{20}=2[/tex]
amount of the substance left after 2 half lives will be=[tex]\frac{32}{2^2}[/tex]=8g.
c) t= 60 seconds
no of half lives=[tex]\frac{60}{20}=3[/tex]
amount of the substance left after 3 half lives will be=[tex]\frac{32}{2^3}=4g[/tex]
d) t= 80 seconds
no of half lives=[tex]\frac{80}{20}=4[/tex]
amount of the substance left after 4 half lives will be=[tex]\frac{32}{2^4}=2g[/tex]
e) t= 100 seconds
no of half lives=[tex]\frac{100}{20}=5[/tex]
amount of the substance left after 5 half lives will be=[tex]\frac{32}{2^5}=1g.[/tex]
The half-life of a radioactive element is defined as the time required by the specific isotope to decrease by half of its original value. The unobtanium after given time will be present as:
After 20 secs, 16 gramsAfter 40 secs, 8 gramsAfter 60 secs, 4 gramsAfter 80 secs, 2 gramsAfter 100 secs, 1 gramHalf-life is the time required by the unobtanium is the half of the reaction is completed. Half of the substance will be decomposed, such that:
Amount of substance left n half-lives = [tex]\dfrac{\text A}{{2}^{\text n}}[/tex]
where A= initial amount of substance
Now,
n = number of half-lives = given time /half-life
Given,
1. Time = t = 20 seconds
Number of half-lives = [tex]\dfrac{20}{20}[/tex] = 1Amount of the substance left after 1 half life = [tex]\dfrac{\text 32}{{2}^{\text 1}}[/tex] = 16 grams.2.Time = t = 40 seconds
Number of half-lives = [tex]\dfrac{40}{20}[/tex] = 1Amount of the substance left after 1 half life = [tex]\dfrac{\text 32}{{2}^{\text 2}}[/tex] = 8 grams.3.Time = t = 60 seconds
Number of half-lives = [tex]\dfrac{60}{20}[/tex] = 1Amount of the substance left after 1 half life = [tex]\dfrac{\text 32}{{2}^{\text 3}}[/tex] = 4 grams.4.Time = t = 80 seconds
Number of half-lives = [tex]\dfrac{80}{20}[/tex] = 1Amount of the substance left after 1 half life = [tex]\dfrac{\text 32}{{2}^{\text 4}}[/tex] = 2 grams.5.Time = t = 100 seconds
Number of half-lives = [tex]\dfrac{100}{20}[/tex] = 1Amount of the substance left after 1 half life = [tex]\dfrac{\text 32}{{2}^{\text 5}}[/tex] = 1 grams.To know more about half-life, refer to the following link:
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How many nitrogen molecules are in a 8.86 L container of nitrogen gas at a pressure of 112.1 kPa and a temperature of 30.8 oC?
What is the theoretical yield in liters of hydrogen at STP if 20.1g of calcium are completely reacted
Rubbing alcohol is 70.% isopropyl alcohol by volume. how many ml of isopropyl alcohol are in a 1 pint (473 ml) container? 330 ml 680 ml 0.15 ml 70. ml 470 ml
Why do covalent compounds tend to have lower melting points than ionic compounds?
The forces of attraction in covalent compounds are weaker than those in ionic compounds as they are formed by sharing of electrons.
What are covalent compounds?Covalent compound is defined as a compound which is formed by the mutual sharing of electrons to form electron pairs between the two atoms.These electron pairs are called as bonding pairs or shared pair of electrons.
Due to the sharing of valence electrons , the atoms are able to achieve a stable electronic configuration . Covalent bonding involves many types of interactions like σ bonding,π bonding ,metal-to-metal bonding ,etc.
Sigma bonds are the strongest covalent bonds while the pi bonds are weaker covalent bonds .Covalent bonds are affected by electronegativities of the atoms present in the molecules.Compounds having covalent bonds have lower melting points as compared to those with ionic bonds.
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The pair of elements that forms a bond with the least ionic character is
A. Na and Cl
B. K and Cl
C. O and Cl
D. Mg and Cl
The pair of O and Cl elements forms a bond with the least ionic character.
The ionic character of the bond depends on the electronegativity difference. The bonds having an electronegativity difference of greater than 1.7 have more ionic character.
(A) In bond between Na and Cl, the electronegativity difference =
Electronegativity of Cl - electronegativity of Na
= 3.16 - 0.93
= 2.23
(B) In bond between K and Cl
= electronegativity of Cl - electronegativity of K
= 3.16 - 0.82
= 2.34
(C) In bond between O and Cl:
= electronegativity of O - electronegativity of Cl
= 3.44 - 3.16
= 0.17
(D) In bond between Mg and Cl:
= electronegativity of Cl - electronegativity of Mg
= 3.16 - 1.31
= 1.85
Since the bond between O and Cl has the least electronegativity difference, thus have the least ionic character.
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Which best describes the tyndall effect? the scattering of light by solutes in a mixture the scattering of light by solvent in a solution the scattering of light by solutes in a solution the scattering of light by particles in a mixt?
the scattering of light by particles in a mixture
Answer:The correct answer is option:'the scattering of light by particles in a mixture'.
Explanation:
Tyndall effect is defined as scattering of the light by the particles present in the mixture. A beam of the light passing through these mixture are visible to the human eyes. Generally colloidal mixture displays this type of effect. The name of his effect is named after the physicist named John Tyndall.
Hence, the correct answer is option:'the scattering of light by particles in a mixture'.
How many moles of KNO3 are needed to make 600 ml of a 1.3M solution?
To make a 1.3M solution with a volume of 600 ml, you would need 0.78 moles of KNO3.
Explanation:To calculate the number of moles of KNO3 needed to make a 1.3M solution, we can use the equation:
Molarity (M) = moles of solute / liters of solution
Rearranging the equation, we can solve for moles of solute:
Moles of solute = Molarity x liters of solution
In this case, the molarity is 1.3M and the volume is 600 ml (which is equivalent to 0.6 L). Substituting these values into the equation:
Moles of KNO3 = 1.3M x 0.6 L = 0.78 moles
Potassium-40 has a half-life of 1.3 billion years. as the potassium-40 isotope decays, it becomes argon. if a rock was formed with 12 g of potassium-40, approximately how long would it take for 75% of the potassium-40 to be replaced by argon?
a. 1.3 billion years
b. 2.6 billion years
c. 5.2 billion years
d. 650 million years
Final answer:
It takes two half-lives, or 2.6 billion years, for 75% of Potassium-40 to decay to Argon, making (b) 2.6 billion years the correct option.
Explanation:
The decay of Potassium-40 (K-40) to Argon (Ar-40) follows the principles of radioactive decay and the concept of half-lives. The half-life is the time it takes for half of the original quantity of a radioactive isotope to decay. In this case, K-40 has a half-life of approximately 1.3 billion years. After one half-life, there would be 6 grams of K-40 and 6 grams of Ar-40. After two half-lives, which is 2.6 billion years, there would be 3 grams of K-40 and 9 grams of Ar-40. Since the question asks for the time it would take for 75% of the potassium-40 to be replaced by argon, we are looking for the time it takes to have only 25% of the original K-40 remaining.
Starting with 12 grams of K-40, after the first half-life, we would be left with 6 grams of K-40, which is 50%. After the second half-life, we would be left with 3 grams of K-40, which is 25% of the original amount. Therefore, it would take two half-lives for 75% of the potassium-40 to decay to argon, which equates to 2.6 billion years. The correct option is therefore (b) 2.6 billion years.
Sedimentary rocks formed from the remains of once-living things are
The correct option is D. This type of rock is called biologic sedimentary rock. It is formed from accumulation of dead living things which have been compressed and cemented together to form a rock.
Please advise if this is your complete question entirely? If yes, then your correct answer is provided above.
Sedimentary rocks formed from the remains of once-living things are ____.
a. metamorphic
c. organic
b. detrital
d. none of the above
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How many sites on this antibody molecule have potential to bind to a non-self molecule?
What kind of reaction occurs when the entropy change of an endothermic reaction is negative?
Gibbs free energy
(G) determines if reaction will proceed spontaneously.
ΔG = ΔH - T·ΔS.
ΔG - changes in Gibbs free energy.
ΔH - changes in enthalpy.
ΔS - changes in entropy.
T is temperature in Kelvins.
When ΔS < 0 (negative entropy change) and ΔH > 0
(endothermic reaction), the process is never spontaneous (ΔG> 0).
Answer:
reaction is nonspontaneous under standard conditions at all temperatures.
Explanation:
took the test.
Which of the following energy yields is most likely to have come from a fission or a fusion reaction?
Answer:
D. 2.0 x 10^11 kJ/mol
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J. J. Thomson’s experiment disproved the theory that an atom is divisible. is indivisible. contains protons. contains electrons.
J.J. Thomson's experiment did not disprove the theory that atoms are indivisible. Instead, his experiment demonstrated the presence of subatomic particles, specifically electrons, within atoms.
The atom's indivisibleness was not refuted by J. J. Thomson's experiment. Instead, his research demonstrated that electrons, a type of subatomic particle, are present in atoms. The "plum pudding" model of the atom was created as a result of Thomson's research from the late 19th and early 20th centuries, which advanced knowledge of atomic structure.
Thomson studied the behavior of electrically charged particles (electrons) inside a vacuum tube in his well-known cathode ray tube experiment. A stream of negatively charged particles (electrons) traveled from the cathode (negative electrode) to the anode (positive electrode) when a voltage was applied across the tube. Thomson came to the conclusion that these particles were the basic building blocks of atoms.
The old belief that atoms were indestructible was refuted by Thomson's discovery of electrons within them, which also supported the notion of subatomic particles inside the atom. His "plum pudding" concept proposed that atoms had a neutral overall charge because electrons were contained within a positively charged "pudding" or matrix.
Later investigations, like those by Ernest Rutherford, helped to clarify our understanding of atomic structure and revealed the existence of a positively charged nucleus that contains protons as well as neutral particles known as neutrons. The existence of indivisible atoms was therefore not refuted by Thomson's experiment, but it did introduce the idea of subatomic particles within atoms, particularly electrons.
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Which of the following is an example of chemical weathering? a. waves washing over rocks on the beach b. acid rain falling on sidewalks c. ice forming in the cracks of rocks d. wind blowing against rocks
Answer:
b. Acid rain falling on sidewalks
Explanation:
Hello,
Acid rain contains majorly carbonic acid [tex]H_2CO_3[/tex] which could react with the concrete that is used to make sidewalks. This chemical reaction, although varies based on the concrete's composition, usually gives off carbon dioxide owing to the acid's instability and leads to the weathering since the sidewalks start to wear out and subsequently break down.
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How are genes related to DNA?
A-Genes are sections of DNA that program the amino acid sequences of proteins.
B-Genes are monomers that are joined by dehydration synthesis to make DNA.
C-Genes are proteins that bind molecules of DNA together to make amino acids.
D-Genes are monomers that are joined by hydrolysis to make DNA.
As the moisture-rich air approaches the mountain, it rises and cools, and water molecules in the air combine to form small drops. the process where water vapor becomes a liquid is called ____________
What is the standard cell notation for an electrolytic cell with aluminum and gold electrodes?
Answer:
Au3+
Explanation:
The standard cell notation for an electrolytic cell with aluminum and gold electrodes Au(s)| Au³⁺ || Al³⁺| Al (s)
What is an Electrolytic Cell ?A device in which electrical energy is converted into chemical energy or chemical energy is converted into electric energy is called an Electrolytic cell
The electrolytic cell consists of two metallic electrodes and an electrolyte.
In this cell nomenclature, the electrode to the left of the salt bridge is always assumed to be the anode, and the accompanying half-equation is always stated as an oxidation , while right side is cathode and the half equation is Reduction.
Reaction at Anode: Au(s) → Au³⁺(aq) + 3e⁻ ..........(oxidation)
Reaction at Cathode: Au³⁺(aq) + 3e⁻ →Au(s) ..............(reduction)
The standard cell notation for an electrolytic cell with aluminum and gold electrodes
Au(s)| Au³⁺ || Al³⁺| Al (s)
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In the formation of a solution how does the solvent differ from the solute
Why can 6-aminohexanoic acid undergo a polymerization reaction with itself?
Answer: Functional groups can lead to intra molecular condensation.
Explanation: 6 -aminohexanoic acid is a molecule which have 2 functional groups - one is amine group (-NH2) and the other one is carboxylic group (-COOH).
The non bonding electrons or lone pairs present on the amine group being nucleophillic in nature will attack on the electrophillic carbon of carboxylic group to form the amide bond, the structure of which is hereby attached.
Thus due to the presence of 2 active functional groups, polymerization with itself can take place easily.
Calculate the theoretical yield if 100.0 g p4o10 react with 200.0 g h2o
A gas sample has a volume of 150 ml at 0.00 ∘c. the temperature is raised (at constant pressure) until the volume is 218 ml. what is the temperature of the gas sample in ∘c at this volume?
A 94.7-g sample of silver (s = 0.237 j/(g · °c)), initially at 348.25°c, is added to an insulated vessel containing 143.6 g of water (s = 4.18 j/(g · °c)), initially at 13.97°c. at equilibrium, the final temperature of the metal–water mixture is 22.63°c. how much heat was absorbed by the water? the heat capacity of the vessel is 0.244 kj/°c.
Q = m*C*dT
m = mass
C = specific heat capacity
dT = Temperature change
Q = heat evolved
Heat lost by metal is equal to the sum of heat taken up by water and vessel. Since water is taken in the vessel so
the initial and final temperatures would be same for vessel and water...
Q = 94.7 *0.237 *(22.63 - 348.25) = 7308.18 Joules = 7.3 KJ
Heat lost by silver = 7.3 KJ
Heat absorbed by water = 143.6*4.18*(22.63 - 13.97) = 5.2 KJ
Describe two negative effects that water pollution can have on the environment. Explain one way water pollution can be reduced.
Answer:
1) Adverse effect on aquatic life also increase in biological oxygen demand.
2) Biomagnification of pollutants
Explanation:
Water pollution is caused by unwanted addition of waste, animal debris, industrial effluents etc in a water body.
Water pollution may cause many direct and indirect harmful effects on environment. To name a few:
a) Decrease in level of oxygen leading to death of aquatic organism like fish.
Increase in biological oxygen demand.
b) Biomagnification: a pollutant may enter food chain from water and some pollutant may enter food chain contaminating other members of food chain.
How much is 2.50 g of CuCl2 in moles ?
How does nh3 and ca(OH)2 form OH- ions in water?
The formula for the illegal drug cocaine is c17h21no4 (303.39 g/mol). what is the percentage of hydrogen in the compound? 21.09% 4.618% 67.30% 6.991% 3.959%
Write out the balanced equation for the reaction that occurs when Mg(OH)2 and HCl react together.
Answer:
The balanced equation for the reaction that occurs when Mg(OH)2 and HCl react together is:
Mg(OH)2+2HCl -------->MgCl2+2H20
How many moles of gas occupy 98 l at a pressure of 2.8 atmospheres and a temperature of 292 k?
"11.46" moles of gas occupy 98 L at 2.8 atm pressure.
Ideal gas equation:The equation characterizing the stages of hypothetical gasses stated mathematically involving combinations of empirical as well as physiological constants, is considered as Ideal gas equation.
According to the question,
Volume occupied, V = 98
Temperature, T = 292 k
Pressure, P = 2.8 atm
By using ideal gas equation, we get
→ PV = nRT
or,
→ n = [tex]\frac{PV}{RT}[/tex]
By substituting the above values, we get
= [tex]\frac{2.8\times 98}{0.082\times 292}[/tex]
= [tex]\frac{274.4}{23.944}[/tex]
= [tex]11.46[/tex]
Thus the above answer is appropriate.
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