percentage of a radioactive sample that remains after four half-lives have passed is 6.25 %
As radioactive substances are first-order reactions and first-order reactions have a constant half-life and are represented by t1/2. t1/2 = 0.693 / λ
half-life is the time period for the sample to become half of its original concentration.
so for 1 st half-life, the substance will become 100 / 2 =50%
for 2 nd half-life, the substance will become 50 / 2 = 25%
for 3 rd half-life, the substance will become 25 / 2 = 12.5%
for 4 th half-life, the substance will become 12.5 / 2 = 6.25%
percentage of a radioactive sample that remains after four half-lives have passed is 6.25 %
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Compare the density values for the solid in part II. The actual density of our solid is 8.9 g/mL. Are the densities of the solid precise and accurate? Explain your answer.
[Answer on your own using the previous question as a guide.]
Part II: Density of Irregular-Shaped Solid – record volume with 1 place after the decimal
Mass of solid (g) [4]
38.951
43.830
41.418
Volume of water (mL) [5]
52.0
51.2
52.4
Volume of water and solid (mL) [6]
56.5
56.1
57.1
The values are not precise but they are accurate because they are all close to the true value of 8.9 g/mL.
What is the density?The density of a solid refers to the ratio of the mass to the volume of the object. This ratio is an intrinsic property because we could use it to identify a substance. In this case, the density of a substance can tell us exactly what the substance is.
Now let us try to obtain the density of the object in each case;
Case 1 = 38.951/56.5 - 52.0 = 8.7 g/mL
Case 2 = 43.830/56.1 - 51.2 = 9.1 g/mL
Case 3 = 41.418/ 57.1 - 52.4 = 8.8 g/mL
It is clear that the values are not precise but they are accurate because they are all close to the true value of 8.9 g/mL.
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What is the hydrogen-ion concentration in a solution formed by titrating 200. ml of 0.16 m hcl with 300 ml of 0.091 m naoh at 25 c?
Hydroxide ion concentration - 0.0094 M. The concentration of hydrogen ions is more conveniently expressed as pH, The logarithm of the reciprocal of the concentration of hydrogen ions in gram moles per liter.
What is Titration?Titration is a common quantitative chemical analysis laboratory technique used to calculate the concentration of a specific analyte. Titrimetric and volumetric analysis are other terms for it (a substance to be analyzed). As the reagent, also known as the titrant or titrator, a standard solution with known concentration and volume is prepared. The titrant reacts with an analyte solution to determine the concentration of the analyte (also known as the titrant). The amount of titrant that interacted with the analyte is referred to as the titration volume. Titration is the slow addition of a known concentration solution (called a titrant) to a known volume of an unknown concentration solution until the reaction reaches neutralization, which is often indicated by a color change.The acid-base reaction equation is as follows:
HCl + NaOH ---> NaCl + H₂O
stoichiometry of HCl to NaOH is 1:1
number of HCl moles - 0.16 mol/L x 0.200 L = 0.032 mol
number of NaOH moles - 0.091 mol/L x 0.300 L = 0.0273 mol
The limiting reactant is NaOH therefore the number of HCl moles reacted - 0.0273 mol
the excess amount of HCl moles is - 0.032 - 0.0273 = 0.0047 mol
since HCl is a strong acid
total volume - 200 mL + 300 mL = 500 mL
[HCl] = [H⁺]
therefore [H⁺] = 0.0047 mol / 0.500 mL
[H⁺] = 0.0094 mol/L
hydroxide ion concentration - 0.0094 M
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In which species does sulfur have the same oxidation state as in so3-2?
a. s2o3-2
b. so4-2
c. h2s
d. socl2
The oxidation state of sulfur in SOCl2 is the same as the oxidation state of sulfur in SO3-2.
To calculate the oxidation state of a particular atom in a polyatomic compound, we need to add the oxidation states of all the elements and put them equal to the charge present on the compound.
The oxidation state of oxygen is generally taken to be -2.
In case of SO3-2, the oxidation state of sulphur is S + 3(-2) = -2, S = +4
Similarly, in the case of the other compounds , the oxidation state of sulfur can be calculated as,
S2O3-2, 2S + 3(-2) = -2, S = +2
SO4-2, S + 4(-2) = -2, S = +6
H2S, S + 2 = 0, S= -2
SOCl2, S + (-2) + (-2) = 0, S = +4
Of all the compounds mentioned above, only SOCl2 has the same oxidation state as sulfur as SO3-2.
Hence, the oxidation state of sulfur in SOCl2 is the same as the oxidation state of sulfur in SO3-2.
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what is the average mass of one atom of titanium
Answer:
47.867 U
Explanation:
The average atomic mass of titanium is calculated by taking the weighted average of the atomic masses of its stable isotopes. Simply put, each isotope i will contribute to the average atomic mass of the element in proportion to its decimal abundance, which is simply the percent abundance divided by 100 .
What happens when an object reaches a state of thermal equilibrium
Select the product or products formed by the proton transfer reaction that occurs when these two substances interact:________
Select the product or products formed by the proton transfer reaction that occurs when these two substances interact: Arrhenius acids.
What is Arrhenius acids?Communication between two or more computer applications is made possible via application programming interfaces (APIs). It is a kind of software interface that provides a service to other software. An API specification is a document or a standard that outlines how to create or use a connection or interface of this type. The term "implement" or "expose" refers to a computer system that conforms to this standard. A specification or an implementation may both be referred to as an API.
An application programming interface, as opposed to a user interface, links computer systems to people, while a user interface does the opposite.
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In an atom, if you change the number of neutrons you get a(n)
-ion
-isotope
-different element
Answer: Isotope
Explanation: It's an isotope because isotopes are atoms with the same number of protons but different neutrons. Ions are atoms have different number of electrons and it wouldn't be a different element because the atom still has the same number of protons.
What will happen If you pour epsom salt on a fire ant mound?
Answer:
It will kill them or harm them
Explanation:
Epsom salt works as a natural safe pesticide for ants and can kill them depending on how u use it.
What coefficients are needed to balance the equation for the complete combustion of methane? enter the coefficients in the order ch4 , o2 , co2 , and h2o , respectively.
The coefficients needed to balance the equation for the complete combustion of methane are 1,2,1 and 2 for methane, oxygen, carbon dioxide, and water respectively.
The equation becomes The equation becomes: CH₄ (g) + 2O₂ (g) -> CO₂ (g) + 2H₂0 (g)
Burning any hydrocarbon element in the presence of O (oxygen) to give CO2 along with light and heat is called a combustion reaction.
Without enough oxygen, the combustion process will be incomplete. To equalize the chemical reaction equation, we need to use variables. Here are a few steps:
Give a coefficient on substances present in the reaction equation such as a, b, or c.Write an equation on the basis of the similarity of the number of atoms where the number of atoms = coefficient × index between reactant & productChoose the coefficient of the element with the most complex chemical formula equal that is equal to 1.If you need to learn more about coefficient in a chemical reaction, click here:
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What difference does it amke that both the nucleophile and electrophile are contained?
Nucleophiles are molecules with electron-rich atoms that donate electrons to form a bond while electrophiles are molecules with electron-deficient atoms that accept electrons.
What is Nucleophiles ?A chemical species known as a nucleophile in chemistry donates an electron pair to create bonds. Any molecule or ion with a free pair of electrons or at least one pi link can function as a nucleophile. Nucleophiles are Lewis bases because they donate electrons to other molecules.
The term "nucleophilic" refers to a substance's propensity to form bonds with positively charged atomic nuclei. Nucleophilicity, also known as nucleophile strength, describes a substance's nucleophilic nature and is frequently used to compare the atoms' affinities. Solvolysis refers to neutral nucleophilic reactions with solvents like alcohols and water. Nucleophiles can engage in nucleophilic substitution, whereby a nucleophile is attracted to a complete or partial positive charge, and nucleophilic addition. Basicity and nucleophilicity are closely linked concepts.
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PLEASE Name five elements of the Periodic Table and name three properties for each element listed. For example, Oxygen: polarity.
Answer:
Hydrogen = colourless, odourless, extremely flammable
Lithium = lowest density, reacts with water, high specific heat
Oxygen = nonpolar, reactive, tasteless
Helium = low boiling point, low density, low solubility
Nitrogen = odorless, colorless, nonflammable
5. the melting and boiling points of sodium metal are much lower than those of sodium chloride. what does this difference reveal about the relative strengths of metallic bonds and ionic bonds? (18.55)
Atoms in a metallic substance are held together by a force called the metallic bond.
What is metallic bonds?The metallic bond is a force that holds the atoms of a metallic substance together. In such a solid, atoms are closely spaced. The outermost electron shell of each metal atom often overlaps with a large portion of its close neighbors.Metallic chemical bonds are created by the electrostatic attraction of conduction electrons and positively charged metal ions. It is possible to imagine free electrons being shared among positively charged ion structures.Ions with opposing charges electrostatically attract one another to form ionic bonds, sometimes referred to as electrovalent bonds, in chemical molecules. A bond of this type is formed when the valence (outermost) electrons of one atom are irreversibly transferred to another atom.Ionic bonding, a type of chemical bonding that involves the electrostatic attraction between two atoms or ions with radically different electronegativities, is the primary interaction in ionic compounds.To learn more about metallic bonds refer to:
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If I need 506.75kg of Al from Al2S3 how many kg of Al2S3 will I need?
The mass of Al₂S₃ in kg required is 2815.28 kg
What is percentage mass of a substance?The percentage mass of a substance is the ratio of the substance in a given substance to that of the total mass of the substance expressed as a percentage.
The percentage mass of aluminum in Al₂S₃ is calculated as follows:
Molar mass of Al = 27 f
Molar mass of Al₂S₃ = 150 g/mol
Percentage mass of Al = 27/150 * 100%
Percentage mass of Al = 18%
Mass of Al₂S₃ required is calculated with the formula:
Mass of Al₂S₃ = mass of Al * 100/percentage mass of Al
Mass of Al₂S₃ = 506.75 * 100/18
Mass of Al₂S₃ = 2815.28 kg
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Yucca mountain, nevada is a potentially viable site for nuclear waste disposal because:________
Yucca Mountain, Nevada is a potentially viable site for nuclear waste disposal because it is an arid desert with very less precipitation and minimal contamination due to the nuclear waste.
Yucca Mountain, Nevada is a wide stretch of 160 km of dry desert with very little rainfall. This area is mainly composed of dense volcanic rock which contains minute pores which make the process of rainwater infiltration very slow and restricting.
Also, the nuclear waste will be stored in such a way that it is far above the water bodies of the mountain. This way the threat of water contamination is also out of question.
These all factors would effectively protect the waste and prevent the leak of harmful radioactive radiation from the disposal storage.
That being the case, Yucca Mountain, Nevada is a potentially viable site for nuclear waste disposal.
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HELP!
which of the following conversion factors are needed to convert from um to km? select all that apply
- 10dm = 1m
- 100cm = 1m
- 1000m = 1km
- 1,000,000um = 1m
The conversion factors which are needed to convert from um to km is 1,000,000um = 1m.
What ia Conversion factor?A conversion factor is defined as a number which is used to convert one set of units to another set of units, by multiplying or dividing by integer or rational number. When a conversion is essential, the appropriate conversion factor in an equal value should be used.
For example, for the convertion of inches to feet, the conversion value which is used to convert is 12 inches equal 1 foot.
Now, as we know that, 1km = 1000m.
It can be concluded that we know how to convert kilometre to metre.
So, we need the conversion factor to convert um to km.
Therefore, we need 1,000,000um = 1 m which is needed to convert um to km.
Thus, we concluded that the conversion factors which are needed to convert from um to km is 1,000,000um = 1m.
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What is the number of lone pairs on the central atom in the lewis structure of icl2- ?
The central atom of ICl2- has three lone pairs in the Lewis structure.
Clarify the Lewis structure.Lewis structures, also known as Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDs), are diagrams that show the covalent bonds that connect atoms in a molecule as well as any lone electron pairs that may be present. Any covalently bonded molecule, as well as coordination compounds, can be given a Lewis structure. Gilbert N. Lewis, who proposed the Lewis structure in his 1916 article The Atom and the Molecule, was named after it. Lewis structures extend the concept of the electron dot diagram by drawing lines between atoms to represent shared pairs in a chemical bond.
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Write a balanced molecular equation for the reaction that occurs when aqueous aluminum nitrate reacts with aqueous sodium sulfide to form aqueous sodium nitrate and an aluminum sulfide precipitate.
The Balanced equation is:
[tex]2Al(NO_3)_3 (aq) + 3Na_2S (aq) \rightarrow Al_2S_3 (s) + 6NaNO_3 (aq)[/tex]
A chemical reaction that has a balanced equation is one in which the total charge and the number of atoms in each of the components, for both the products and the reactants, are exactly equal. Simply said, each side of the reaction process has an equal mass and charge.
A chemically balanced equation is a symbolic representation of a chemical reaction that consists of symbols and formulas, in which a + sign separates the entities in both the reactant and product lists on the left and right, respectively, products and the reactants and an arrow pointing in the direction of the products to indicate the reaction's direction. The critical values of the stoichiometric numbers are shown as coefficients alongside the symbols and formulas of the entities.
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Which of the following is true?
a Liquids are denser than gases
b Liquids are less dense than gases
c Liquids and gases are the same density
d None of the above
Density of liquids is more than that of gases. Thus, the correct answer is (a).
A liquid has molecules that are closely spaced out. As a result, liquids have a higher density than gases.
The mass of a material per unit of volume is its density. Density is most frequently represented by the symbol ρ, but Latin letter D may also be used.
The amount of items in a space—which might include humans, animals, plants, or objects—is referred to as the space's density. Divide the number of items by the area's measurement to determine density. A country's population density is calculated by dividing its total population by its area, expressed in square kilometres or miles.
In comparison to liquids and gases, solids are denser than liquids and gases, respectively. The solid's particles are close to one another and have very little room to move. In a liquid, the particles are often still in contact, although there are gaps between them. There are considerable gaps between the gas particles.
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Draw the dipole for PBr3
The dipole for PBr3 is shown in the attachment. PBr3 has non xero dipole moment because bromine atoms can not cancel out dipole moment of each other.
The three bromine atoms in this molecule do not cancel out the dipole moment of each other and molecule shows net dipole moment.it shows that PBr3 is a polar molecule.the partially positive charge surrounded by phosphorus atom and partially negative charged surrounded by bromine atom.
Dipole moment is used to define the symmetry of molecules. PBr3 has the trigonal pyramidal structure. bromine atom has more electronegative value than phosphorus.
Thus, the dipole moment in PBr3 is non zero due to unequal charge distribution.
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If astronauts landed on a planet 2/3 the size of earth what would it be
Answer: The ratio of radii of earth to another planet is 2/3 and the ratio of their mean densities is 4/5. If an astronaut can jump to a maximum height of 1.5 m on the earth, with the same effort, the maximum height he can jump on the planet is
Explanation:
H3C
ОН
С.
Н
CH3
what is the name of molecule y
[tex]H_3[/tex]CОНС = acetaldehyde also known as ethanal ( It is a carbonyl compound)
НC[tex]H_3[/tex] = methane ( it is a hydrocarbon of alkane group)
Methane is a colorless odorless flammable gaseous hydrocarbon C[tex]H_4[/tex] that is a product of decomposition of organic matter and of the carbonization of coal, is used as a fuel and as a starting material in chemical synthesis, and is the simplest of the alkanes. methane gas produced when vegetation decomposes in waterethanal is a Volatile liquid - collect in ice bath and Colourless, its Density: 788 kg/m³ , its Molar mass: 44.05 g/mol and its Melting point: -190.3°F (-123.5°C)To know more about acetaldehyde visit :
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Which of the following equations shows a chemical change?
O NH3(g) → NH3(1)
O C3H8 +5023CO2 + 4H₂O
O C₂H5OH(1)→ C₂H5OH(g)
O H₂O(s)→ H₂O(g)
A lake contains 0.05 mg po4 3- /l (orthophosphate). what is the concentration expressed in:
The answer is ppm that is parts per million.
This stands for "parts per million" and can also be written as mg/L (milligrams per liter). The mass of a chemical or contamination per volume of water is the unit of measurement here. On a lab report, ppm or mg/L both mean the same thing. The solution makes up 0.0001 percent of 1 PPM. It is equivalent to 1 mg in other measures like milligrams per kilogram, milligrams per liter of water, etc. Additionally, it is the 1/1,000,000th of something. PPM stands for one (1/,000,000) (defect or incident). Previously, suppliers were deemed to be of high quality if their failure rate was less than 10,000 PPM, or 1%.
The complete question is- A Lake Contains 0.05 Mg PO 2-/L (Orthophosphate). What Is the Concentration Expressed In:
A. Ppm
B. M (Molar)
C. Mg PO-P/L
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Which of the wavenumbers given corresponds to the c=o double bond region on an ir spectrum?
1600 - 1850 cm-1 wavenumber corresponds to the C=O double bond region on an IR spectrum.
Which of the following are wavenumber units in IR spectroscopy?Wavenumbers are the most commonly used units in infrared spectroscopy.IR spectroscopy examines radiation with wavelengths ranging from 40 to 13,000 cm^-1.The stretching frequencies of most alkyne CC bonds range between 2100 and 2200 cm^-1. Terminal alkynes typically produce moderately intense CC stretching signals.IR spectroscopy can be used to determine which functional groups are present in a compound. The IR spectrum is created by recording the frequencies at which a polar bond's vibration frequency is equal to the infrared light's frequency.Infrared spectroscopy (IR spectroscopy) is the study of the electromagnetic spectrum's infrared region, which contains light with a longer wavelength and lower frequency than visible light. It covers a variety of techniques, the majority of which are based on absorption spectroscopy.To learn more about wavenumber of the C=O double bond refer to
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How many orbitals are completely filled in an atom that has 14 electrons? The electron configuration is 1s22s22p63s23p2.
Is making carbon dioxide possible? If so, how do you make it? What's the formula?
Answer:
yes
Carbon dioxide is produced whenever an acid reacts with a carbonate.
Explanation:
How to make carbon dioxide -
You can make CO2 by adding 1 tablespoon of white vinegar and 1 heaping teaspoon of baking soda in a glass. This safe chemical reaction creates water and CO2.
Formula -
The chemical formula for carbon dioxide is CO2.
A compound of iodine and cesium contains 69.75 g of metal and 65.40 g of nonmetal. how many grams of cesium are in 30.84 g of compound?
The mass of cesium in 30,84 g of compound will be 14.92 g. It can be calculated by the mass of Iodine and Cesium which are combining to form the compound.
Weight of metal which is cesium=65.40g
Weight of non metal which is Iodine= 69.75g
Weight of compound= 135.15g
135.15 g of compound contains 65.40 g of cesium
Therefore,
135.15 g of compound= 65.40 g of cesium
1 g of compound = 65.40/ 135.15 g of cesium
=0.4839g of cesium
30.84 g of compound contains 0.4839× 30.84 g of cesium
=14.92 g of cesium.
So , by using equality and proportion method, weight of cesium will be calculated as 14.92 g.
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Measurements show that unknown compound X has the following composition:
element mass %
carbon 40.9%
hydrogen 4.57%
oxygen 54.4%
Write the empirical chemical formula of X.
The empirical formula of the compound is CHO.
What is the empirical formula?The empirical formula is the formula that shows the ratio of each of the atoms in the compound. Let us now look at the relative percentages of each of the elements and divide them by the relative atomic masses of each of the elements.
C - 40/12, H - 4.57/1, O - 54.4/16
C - 3.33, H- 4.57, O - 3.40
Dividing through by the lowest ratio;
C - 3.33/3.33, H- 4.57/3.33, O - 3.40//3.33
C - 1, H - 1, O - 1
The empirical formula of the compound is CHO.
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(b) Describe how the arrangement of electrons in a strontium atom is:
(i) similar to the arrangement of electrons in a calcium atom
(ii) different from the arrangement of electrons in a calcium atom.
The electronic configuration of in a strontium atom is similar to the arrangement of electrons in a calcium atom as they have same number of valence electrons, 2.
The electronic configuration of in a strontium atom is different from the arrangement of electrons in a calcium atom as they have different number of electron shell electrons, which is 4 and 5 respectively.
What is electronic configuration of atoms?Electronic configuration of atoms refers to the arrangement of the electrons in an atom in orbits or shells around the nucleus of the atom of the element.
Electronic configuration of atoms of elements forms the basis of the arrangement of the periodic tale into groups and periods.
Elements that have the same number of electrons in their valence or outermost shell are found in the same group and elements that have the same number of electron shells are found in the same period.
Comparing the electronic configuration of calcium and strontium as follows below:
Electronic configuration of calcium is 1s²2s²2p⁶3s²3p⁶4s²
Electronic configuration of strontium is 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²
Calcium and strontium have the same number of outermost shell electrons, which is 2. Therefore, they belong to same group.
Calcium and strontium have the different number of electron shell electrons, which is 4 and 5 respectively. Therefore, they belong to different periods.
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how are ionic bonds formed between k and br
Ionic bonds are formed between K and Br due to losing and gaining of electrons.
Ionic bond is the bond formed between two elements due to the gaining and losing of electrons by the one member and acceptance by the other member.
Usually the metal atom loses electron and the non-metal gains electron.
Ionic bond is formed between Potassium (K) and Bromine (Br). Potassium loses electron to form K⁺ and Bromine gains electron to form Br⁻ .
Potassium Bromide (KBr) is formed due to formation of K⁺ and Br⁻ after the addition of electron is Br and losing of electron by K atom.
Potassium Bromide can be Electrolysed into the constituent ions on addition of water due to its nature as a strong electrolyte.
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