The average atomic mass of strontium reported to two decimal places is 87.62 amu
The average atomic mass of an element may be determined by adding the atomic mass units of all its isotopes and dividing the result by the abundance percent/100.The average atomic mass of strontium (Sr) = [(atomic mass of Sr-84)(Abundance / 100) + (atomic mass of Sr-86)(Abundance / 100) + (atomic mass of Sr-87)(Abundance / 100) + (atomic mass of Sr-88)(Abundance / 100)].The average atomic mass of strontium[tex](Sr) = [(83.913428)(0.0056) + (85.909273)(0.0986) + (86.908902)(0.07) + (87.905625)(0.8258)][/tex]= 87.6166 amu ≅ 87.62 amu.The weighted average mass of the atoms in a naturally. The average atomic mass, commonly referred to as atomic weight, is a naturally occurring sample of an element. The standard units for expressing average masses are unified atomic mass units (u), where 1 u equals precisely one-twelfth the mass of a neutral atom of carbon-12.To learn more about average atomic mass visit:
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True or false: Properties that cannot be observed are due to the structure of atoms and molecules that can be observed.
Properties that cannot be observed are due to the structure of atoms and molecules that can be observed.
The correct option is True.
What are molecules?A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds.
It is true that properties that cannot be observed are due to the structure of the atoms and molecules of that matter.
Physical properties are often referred to as those properties we can observe with our eyes.
Molecules made up of two or more elements are called compounds Example of molecules includes water, calcium oxide, glucose etc.
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which material is said to have a high permeability? group of answer choices nickel bismuth soft iron
Iron l is said to have a high permeability. High coercivity, high retentivity, and high permeability materials make up the permanent magnets. An object made of a substance that has been magnetized and produces its own persistent magnetic field is referred to as a permanent magnet.
In contrast to an electromagnet, which is made of a coil of the wire wrapped around a ferrous core and needs an electric current to create a magnetic field, a permanent magnet's magnetism is "always on" and it creates its own permeability magnetic field. A common example is a refrigerator magnet used to the keep notes on the door of the refrigerator.
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Solution a has a hydrogen ion concentration of 3. 2 x 10-9 and solution b has a hydrogen ion concentration of 6. 9 x 10-5. Which solution is more basic?.
Solution a is more basic.
Basic solutions are those solutions whose pH is greater than 7.
The pH of a solution is calculated or determined by the hydrogen ion concentration of the solution. The relation between pH of a solution and the hydrogen ion concentration in it is given by :
pH = -log[ H+]
From this relation we can conclude that if the hydrogen ions concentration in a solution is more , the value of pH will become lower.
For Solution a, the pH is given by :
pH(a) = -log [ 3.2 x 10^-9 ] = 8.4948 ≅ 8.5
For Solution b, the pH is given by :
pH(b) = -log [ 9 x 10^-5 ] = 4.04 ≅ 4
Since the pH of solution b is lower than the pH of solution a , solution a is more basic than solution b. Moreover, the pH of solution a is approximately 8.5 which makes it a moderately strong basic solution.
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Based on the amino acid sequences of each histone, estimate the charge of a histone octamer at ph 7. Assume that histidine residues are uncharged at this ph.
The charge on histone octamer at ph7 is +146.
What are histones and how the charge on histone octamer at ph7 is +146?In genetics we read about DNA, but there is a term histone also , simply it is the structure around which DNA wraps.Histone is made of proteins , arginine and lysine.The number of negative charges is 9 , and the number of positive charged is 26.We call it histone octamer because it is made up of eight protein sub units.We use histone octamer , along with DNA for packaging purposes, in nucleosome is also a commonly used term.Nucleosome consist of 200 base pairs.To know more about histone visit:
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an agricultural chemist wished to study the effect of varying fertilizer applications on the growth of tomato plants. the chemist prepared a "stock" aqueous solution of urea, (nh2)2co, by dissolving 1.75 g of this compound in water to make 1.00 l of solution. then she prepared a series of more dilute solutions to apply to her tomato plants. one of these solutions contained 5.00 ml of "stock" solution diluted to give a final volume of 25.00 ml. what was the concentration of urea in this diluted solution?
The concentration of Urea in final solution will be [tex].00725[/tex] M.
We know that
[tex]M_1/M_2 = V_1/V_2[/tex]
where
[tex]M_1[/tex] is the concentration of solute in first solution
[tex]M_2[/tex] is the concentration of solute in second solution
[tex]V_1[/tex] is the volume of first solution
[tex]V_2[/tex] is the volume of second solution
According to question,
Solute is Urea whose molecular weight is 60gm
1,75 gram of urea is used
Therefore moles of urea used = [tex]1.75/60[/tex]
= .029
Molarity of urea = [tex].029/1L[/tex]
= .029
Volume of first solution = 5ml
Volume of second solution = 20ml ( [tex]25 - 5 = 20[/tex])
Therefore,
[tex].029/M_2 = 5/20[/tex]
[tex]M_2 = .00725[/tex]
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which best explains why ionization energy tends to decrease from the top to the bottom of a group? the number of orbitals decreases. the number of neutrons decreases.
Ionization energy tends to drop from the top to the bottom of a group as electrons move away from the nucleus.
What does the periodic table's ionisation energy mean?All elements in the periodic table possess ionisation energy, also known as ionisation potential.
what does "ionisation energy" mean?It is the energy needed to remove one electron from a neutral atom, which results in the formation of an ion.
High ionisation Energy: What Does It Mean?The neutral atom's loosest electron is removed by the first ionisation energy, but the amount of protons acting as an attractive force on the remaining electrons remains constant. This implies that it will be harder and more energy-intensive to remove a second electron.learn more about Ionization energy here
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the question you are looking for is
Which best explains why ionization energy tends to decrease from the top to the bottom of a group?
A.The number of orbitals decreases.
B.The number of neutrons decreases.
C.Electrons get closer to the nucleus.
D.Electrons get farther from the nucleus.
calculate the density of a liquid with a total mass of 88.30 grams and a volume of 165.0 milliliters.
The liquid with a total mass of 88.30 grams and a volume of 165.0 milliliters has a density of: 0.5351 g/ml
To solve this problem the formula and the procedure that we have to use is:
d = m/v
Where:
d= densitym= massv= volumeInformation about the problem:
m = 88.30 gv= 165.0 mld=?Applying the density formula we get:
d = m/v
d = 88.30 g/165.0 ml
d = 0.5351 g/ml
What is density?It is a physical quantity that expresses the ratio of the body mass to the volume it occupies.
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(Bonus) Which element is more reactive? (1 pt)
*
1 point
Sodium
Neon
They are equally reactive
PLEASE HELP MEEE
The concentration of a basic solution is determined by which of the following?
Select one:
a. The number of base molecules in solution.
b. The degree of dissociation of base molecules in solution.
c. The rate at which a base solution neutralizes an acid solution.
d. The temperature of the solution.
The concentration of a basic solution is determined by the degree of dissociation of base molecules in solution (option B).
What is a basic solution?A basic solution is an aqueous solution containing more OH-ions than H+ions.
In other words, a basic solution can be said to be an aqueous solution with a pH greater than 7, which is the neutral range.
The concentration of a basic solution is a function of the OH- ions in the solution. Therefore, the concentration of a basic solution is determined by the degree of dissociation of base molecules in solution.
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Neon and sodium differ by 1 proton (Neon has 10, Sodium 11) but they react VERY differently. Why does this small change cause such a big effect?
The reason why this small change between Neon and sodium cause a very big effect is simply because neon is a noble gas with an octet structure in its electronic configuration while sodium is an alkali metal which is univalent electropositive element.
However, despite the fact that these two different elements has a difference of one electron in their outermost shell, yet they individually carry and posses very powerful electronic structure due to their position in the periodic table which makes them react differently
What is an element?An element can simply be a chemical substance which cannot be split into simpler forms by an ordinary chemical process.
Consider the following differences between Neon and sodium in the periodic table:
Sodium belong to group 1 of the periodic table while Neon belong to group 0 or the 8th groupSodium has a valence electron of just 1 electron while Neon has a valence electron of 8 electrons Sodium is an alkali metal while Neon is a noble gasSo therefore, the reason why this small change between Neon and sodium cause a very big effect is simply because neon is a noble gas with an octet structure in its electronic configuration while sodium is an alkali metal which is univalent electropositive element.
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consider the equilibrium that exists for a saturated aqueous solution of pbcl2. pbcl2s⇄pb2 aq 2 cl-aq which expression gives the solubility product constant ksp for pbcl2 if the [pb2 ]
The solubility product is 4n³.
The equilibrium constant for a solid's dissolving into an aqueous solution is called the solubility product constant. It is represented as K(sp).
A solution is said to be saturated when it has dissolved all of the solutes it can. At a certain temperature, no additional solute can dissolve in a saturated solution.
Consider the equilibrium for a saturated PbCl₂ aqueous solution.
PbCl₂(s) ⇄⇄ Pb₂ (aq) + 2Cl⁻ (aq)
The equilibrium constant for the dissociation reaction of the PbCl₂ solution is:
K(sp) = [Pb²⁺] [Cl⁻]²
Now, [Pb²⁺] = n mol/L
In the solution, there is one-mole Pb²⁺ and two moles of Cl⁻ .
Therefore,
[Cl⁻] = 2n mol/L
So, the equilibrium constant for the dissociation reaction will be:
K(sp) = [Pb²⁺] [Cl⁻]²
K(sp) = n × (2n)²
K(sp) = n × 2n × 2n
K(sp) = 4n³
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Explain why gases are compressible, but solids and liquids are not.
Answer:
The reason why solids and liquids can't compress is because there is no space between the individual particles, so they cannot pack together
Explanation:
The kinetic-molecular theory explains why gases are more compressible than either liquids or solids. Gases are compressible because most of the volume of a gas is composed of the large amounts of empty space between the gas particles.
You have a substance with a half-life of 9 days. How much of it will be left after 36 days?
Answer:
A half life is the amount of time it takes for half of a mass of a given radioactive element to decay to something else. 36 days is 4 1/2 life cycles, so by running 1/2*4 , we get how much of the original substance would be left. That would be 1/16 of the original substance left.
Explanation:
Of course, this is not always perfect, and can vary. In addition, if less than 16 atoms of the original substance are present, there is instead a 1/16∗a chance of at least one remaining.
The amount of substance left after 39 days will be 1/16th of the original amount.
What is the half-life of a radioactive element?The half-life period of the radioactive material can be defined as the time required to reduce its actual amount to half after disintegration. The half-life period of a radioactive substance is independent of the initial amount of the substance.
Consider that N₀ is the initial amount of the substance
Consider that 'n' is the number of half-lives of given substance.
The time for which substance decay, t = 36 days
Half-life of substance (t½) = 9 days
t = n ×t½
36 = n × 9
n = 4 days
Assume that N is the amount of the substance after decay for 39 days.
N ×2⁴ = N₀
N × 16 = N₀
N = N₀/16
Therefore, one-sixteenth of the initial amount of the substance will be left after 39 days.
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6. Which of the following examples describes
a physical change?
Answer:
•Melting of solid ice
• Evaporation of liquid
• Sublimation of solid cheese
since we don’t know the examples I can’t really answer your question but I can say a physical change alters the form or appearance of matter but doesn’t turn any substance in the matter into a different substance once you provide me with the examples I’ll let you know ok
An oxide of iron is found to be 70. 00% iron by mass. Determine the empirical formula for this compound and name it.
The empirical formula of the compound is Fe2O3 and its name is Iron(III) oxide or ferric oxide.
The oxide of iron has 70% of iron by mass.
This means that in every 100 grams of this oxide,70 grams is of iron and the other 30 grams are of oxygen.
To calculate the empirical formula, we have to first find the number of moles of iron and oxygen by dividing the given mass by their molar mass.
Moles of iron = 70/56 = 1.25 moles
Moles of oxygen = 30/16 = 1.875 moles
Now we need to divide the moles of iron and oxygen by the lowest common number i.e. 1.25
Moles of iron/1.25 = 1.25/1.25 = 1
Moles of oxygen/1.25 = 1.875/1.25 = 1.5
The ratio of iron(Fe): to oxygen(O) comes out to be 1:1.5.
Hence, we should multiply this ratio by 2 to get a whole number.
The ratio of Fe:O comes out to be 2:3.
Thus, the empirical formula of the compound is Fe2O3 and its name is Iron(III) oxide or ferric oxide.
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Explain how the solubility of water is useful in maintaining various life processes
The solubility of water is useful in maintaining various life processes because its capability to dissolve a variety of molecules.
Water is a “universal" solvent.
The ability of water to function as a versatile solvent arise from the structure of water molecules are because:
Water molecules form hydrogen bonds with atoms that are part of polar covalent bonds other molecules.
Water's versatility as solvent arises from the polar covalent bonds of water molecules.
Hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen atom (H), covalently bound to a highly electronegative atom such as flourine (F), oxygen (O) and nitrogen (N) atoms.
In water, atoms of hydrogen (H) and oxygen (O) are connected by polar covalent bonds.
Covalent bond is bond between nonmetals. Hydrogen and oxygen are nonmetals.
Solvation is the interaction of solvent (water) with molecules or ions (for example K⁺ and I⁻) in a solute.
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What is a mathematical formula you can make to determine the mass number?
Answer:
Together, the number of protons and the number of neutrons determine an element's mass number: mass number = protons + neutrons.
Sorry about asking this question again. I figured out the number of protons electrons and neutrons. 92,92 and 146. The mass number and atomic number are 238 and 92. I still can't figure out how to find the charge. The internet says +92, but I don't know how that works.
If you see the nuclide notation of uranium (u).
The letter in the mid is the symbol of the element.
The number in the bottom left corner is atomic number (Tells you the number of protons)
The number on the upper left corner is the mass number (equal to the mass number ; = the neutrons and protons added together)
At the last, the charge is on the upper right corner, if there is no +ve and -ve symbol then the charge is neutral.
To find the number of neutrons, protons and electron :
1. No. of protons = Atomic Number (Z)
2. No. of neutrons = Mass number (A) - Atomic number(Z)
3. No. of electrons = Atomic number - Charge
To find the charge it is find by the periodic table suppose group 1 alkali metals have +1 charge and in the same way group 16 -2 charge .
Uranium is a radioactive element and hence it is an alpha particle and hence it has a positive charge.
There are many radioactive element who are alpha particles like thorium and plutonium. Beta particles have negative charge.
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ernest rutherford developed an experiment that showed protons can pass through gold atoms untouched and/or un-deflected. sometimes the protons were deflected by something, but this did not happen too often. most of the atoms pass straight through. his experiment changed the way scientists viewed the structure of an atom. what conclusion did rutherford draw from his experiment?
Rutherford conclusion was: Inside of the gold atom consists of empty spaces.
Rutherford theorized that atoms have their charge concentrated in a very small nucleus.
This was famous Rutherford's Gold Foil Experiment: he bombarded thin foil of gold with positive alpha particles (helium atom particles, consist of two protons and two neutrons).
Rutherford observed the deflection of alpha particles on the photographic film and notice that most of alpha particles passed straight through foil.
That is different from Plum Pudding model, because it shows that most of the atom is empty space.
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A student poured 25 grams of sugar
into a beaker containing 100 milliliters
of water. What is the mass of the
mixture after the sugar dissolves?
If limestone (CaCO3) is heated, 2.8Kg of calcium oxide (CaO) and 2.2Kg of carbon dioxide are produced.
a. Write the balanced chemical equation.
b. Determine mass of the used limestone
The balanced chemical equation is CaCO3---> CaO+CO2 and the mass of the used limestone is 5.0 kg
The heating of limestone yields calcium oxide and carbon dioxide. It is a decomposition reaction.
The reaction is as follows;
CaCO3---> CaO+CO2
According to the law of conservation of mass, mass is conserved in a reaction,
So the mass of limestone used will be (2.8+2.2=5.0 kg)
All balanced chemical equations follow the law of conservation of mass.It says mass is neither created nor destroyed but conserved during a reaction.That is to say, the mass of any one element at the start of a reaction will be equal to that element's mass at the conclusion of the reaction.To learn more about conservation of mass visit:
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here are four sketches of substances. each sketch is drawn as if a sample of the substance were under a microscope so powerful that individual atoms could be seen. decide whether each sketch shows a sample of an element, a compound, or a mixture.
Substance X - compound because it is a combination of elements
Substance Y - Mixture because it is a combination of substances
Substances Z - Element because it contains atoms
Substance T - compound because it is a combination of elements
What are the samples?We know that an atom is the smallest particle of a substance that can take part in a chemical reaction. A compound is formed by a mixture of atoms. An element is obtained as the smallest independent part of a substance.
Now let use classify the samples shown in the images attached.
Substance X - compound because it is a combination of elements
Substance Y - Mixture because it is a combination of substances
Substances Z - Element because it contains atoms
Substance T - compound because it is a combination of elements
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you wish to make 0.357m nitric acid from a stock solution of 3.00m nitric acid. how much concentrated acid must you add to obtain a total volume of 150ml of the dilute solution
17.85 mL of 3.0 M stock solution of nitric acid is needed to make a 150 mL 0.357 M nitric acid.
The dilution of a stock solution can be solved by using the formula below, which indicates that the concentration of the solution changes but the number of moles of the solute remains the same.
(concentration of stock solution)(volume of stock solution) = (concentration of diluted solution)(volume of diluted solution)
Given:
Stock solution: 3.0 M nitric acidDiluted solution: 150 mL of 0.357 M nitric acid(3.0 M)(volume of stock solution)=(0.357 M)(150 mL)
volume of stock solution = [(0.357 M)(150 mL)] / (3.0 M)
volume of stock solution = 17.85 mL
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write the empirical formula for at least four ionic compounds that could be formed from the following ions: mno−4, fe2 , bro−3, nh 4
KMnO4; NaMnO4; LiMnO4
FeO ; FeCl2; FeS ; FeSO4
HBrO3; KBrO3; NaBrO3; LiBrO3
PbO2; PbS2; Pb(SO4)2; Pb(CO3)2
Ionic compounds are made up of charged particles called ions, which are created when an atom (or group of atoms) gains or loses an electron. An ion is classified as either positively or negatively charged depending on its charge.
What is an Emperical formula ?Chemical formulas for compounds that simply specify the proportions of the elements they contain rather than the exact number or arrangement of atoms are known as empirical formulas. The element in the compound with the lowest whole number ratio would be this one.
An empirical formula is used to indicate the simplest whole-number ratio of the various atoms in a molecule. The molecular formula indicates the precise number of different atom kinds that are present in a compound's molecule.Learn more about Emperical formula here:
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A yellow-gold sphere has a mass of 15.2g when passed in the orange liquid the volume was 43ml
A yellow-gold sphere has a mass of 15.2 g when passes in the orange liquid with volume 43 mL
Density= mass/volume
Density = 15.2 g/ 43mL
Density = 0.35 g/mL
Question is to find density
The experiments of wöhler, kolbe, miller, and other chemists invalidated the concept of vitalism by demonstrating that _____.
The experiments of wöhler, kolbe, miller, and other chemists invalidated the concept of vitalism by demonstrating that B) organic molecules could be produced apart from living organisms using inorganic materials.
Concept of vitalism propose that organic molecules could only be synthesised by living organism. Modern science said that vitalism has no credibility.
Adolph Wilhelm Hermann Kolbe (1818 - 1884) contributed to invalidate the concept of vitalism. He made the organic substance acetic acid from inorganic carbon disulfide.
Friedrich Wöhler (1800 - 1882) synthesis of the organic compound urea from inorganic substances.
Abiotic factors are non-living chemical and physical things of the environment.
Abiotic factors can include water, light, radiation, temperature, humidity, atmosphere, and soil.
On the contrary, biotic factors are all of the living organisms within an ecosystem.
Missing options:
A) carbon atoms were common in both living organisms and nonliving substances such as rocks and soil
B) organic molecules could be produced apart from living organisms using inorganic materials
C) tissues extracted from living organisms could still promote organic reactions
D) one organic substance could be transformed into another organic substance
E) complex organic substances are the result of a series of sequential synthetic reactions occurring in both living organisms and nonliving systems.
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someone can anyone answer this question pleaseeee ?
Which statement about bases is true?
(a) They are all alkalis
(b) They can neutralize acids
(c) They are all soluble
answer this question pleaseeeeeeeeeeeee
Answer:
either (a) or (b)
Titanium (Ti, #22) atoms bond with Oxygen (O, #8) atoms. What type of bond will hold them together? (1 pt)
*
1 point
ionic
covalent
metal
intermolecular (hydrogen, dipole, etc.)
Titanium (Ti,) atoms bond with Oxygen (O,) atoms. covalent type of bond hold them together.
What is covalent bond?An electron exchange that results in the formation of electron pairs between atoms is known as a covalent bond.
When atoms share electrons, a permanent equilibrium of the attractive and repulsive forces between them is known as covalent bonding.
These electron pairs are referred to as shared pairs or bonding pairs.
Thus ,Titanium (Ti,) atoms bond with Oxygen (O,) atoms. covalent type of bond hold them together.
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an unknown solution has a ph of 7.2. which of these chemicals is likely to cause the greatest decrease in the ph of the solution when added to the solution? (5 points) hf koh nh3 hno3
The largest pH lowering agent is HNO3 . We need to add more H3O+ to the solution in order to reduce the pH.
What is pH and why is it significant?A solution's pH is a significant indicator of its chemical composition.The pH can affect how readily available nutrients are, how biological processes work, how bacteria behave, and how chemicals behave.How is pH determined?
There are two ways to measure pH: colorimetrically with indicator fluids or sheets and electrochemically with electrodes and a millivoltmeter for greater accuracy (pH meter).
Why is pH in water important?To maintain your body in equilibrium and to control metabolic processes, water pH is crucial. A diet that is too alkaline may prevent critical nutrients from being metabolised, while a diet that is too acidic will cause weight gain, a slowed immune response, and increased susceptibility to disease.learn more about pH here
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Paint is a type of mixture called a(n) ____________ because it is a
heterogeneous mixture with large particles that will settle to the
bottom if undisturbed for a long period of time.