Answer:
Where is the picture? Can't answer without it.
The half-life of a radioactive substance is 15 days. After 10 days a sample of the substance has been reduced to a mass of 4 mg. A. What was the inital mass (in mg) of the sample? B. Using your answer from above, after how many days will there only be 0. 3 mg of substance left?.
A. The initial mass of the sample is 6.35
B. The time taken for 0.3 mg of the sample to remain is 66 days
A. Determination of the initial mass of the sample
We'll begin by calculating the number of half-lives that has elapsedHalf-life (t½) = 15 days
Time (t) = 10 days
Number of half-lives (n) =?n = t / t½
n = 10 / 15
n = ⅔Finally, we shall determine the initial mass of the sample.Number of half-lives (n) = ⅔
Amount remaining (N) = 4 mg
Initial amount (N₀) =?[tex]N_0 = N \times {2}^{n} \\ N_0 = 4 \times {2}^{2 \div 3} \\ N_0 = 6.35 \: mg[/tex]
Therefore, the initial mass of the sample is 6.35 mg
B. Determination of the time
We'll begin by calculating the number of half-lives that has elapsedAmount remaining (N) = 0.3 mg
Initial amount (N₀) = 6.35 mg
Number of half-lives (n) =?[tex]{2}^{n} = \frac{N_0}{N} \\ \\ {2}^{n} = \frac{6.35}{0.3} \\ \\ {2}^{n} = 21.167 \\ take \: the \: log \: of \: both \: side \\ log \: {2}^{n} = log \: 21.167 \\ nlog2 = log \: 21.167 \\ divide \: both \: side \: by \: log2 \\ \\ n = \frac{log \: 21.167}{log2} \\ \\ n = 4.4[/tex]
Finally, we shall determine the timeNumber of half-lives (n) = 4.4
Half-life (t½) = 15 days
Time(t) =?t = n × t½
t = 4.4 × 15
t = 66 daysTherefore, it will take 66 days for 0.3 mg of the sample to remain.
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What is the mass of 1 mol of 0 atoms to three significant figures?
Answer:
16.0 gms
Explanation:
what is the mass of 1 mole of O atoms to 3 significant figures
go to your periodic table.......O is element 8 and has an atomic mass of 15.999. to 3 significant figures, this rounds to 16.0
1 mole is the molar mass in grams
so 1 mole of O atoms has a weight of 16.0 gms
What is the formula for the ionic compound formed by calcium and selenium?
Answer:
CaSe
Explanation:
not sure!!
when the corporation issuing the bonds has the right to redeem the bonds prior to the maturity, the bonds are
Answer:
Callable or redeemable bonds
Explanation:
"..are bonds that can be redeemed or paid off by the issuer prior to the bonds' maturity date."
why the mixture of bromine and ethane is discoloured when left in the sun
Answer:
In the presence of UV light, ethane will react with bromine in a substitution reaction. UV light is the condition under which the reaction will occur so it is written above the arrow in the chemical equation. As the reaction proceeds, the intensity of the re-brown colour of the bromine water decreases.
Answer:
here ya go
Explanation:
combining bromine and ethane leads to a brown gas or liquid which is made of the elements. it is a gas at room temperature and does not affect human beings. there are many uses for bromine compounds but they are mainly used for the manufacturing of chlorine, fire retadants, water purification, graphy chemicals and pharmaceutcals. it is a naturally occurring element that can be found in animals such as sharks since they produce their own.
Q.2. Which of the following statements is true of second ionization energies?
a) That of Al is higher than that of Mg because Mg wants to lose the second electron, so it is easier to take the second electron away
b) That of Al is higher than that of Mg because the electrons are taken from the same energy level, but the Al atom has one more proton
c) That of Al is lower than that of Mg because Mg wants to lose the second electron, so the energy change is greater
d) That of Al is lower than that of Mg because the second electron taken from Al is in a p orbital, so it is easier to remove it.
Answer:
a) That of Al is higher than that of Mg because Mg wants to lose the second electron, so it is easier to take the second electron away
Statement which is true regarding second ionization energy is that ionization energy of of Al is higher than that of Mg because Mg wants to lose the second electron, so it is easier to take the second electron away.
What is ionization energy?Ionization energy is defined as the minimum amount of energy required to remove an electron which is loosely held in the outermost shell to form an isolated gaseous atom,ion or molecule.
It has a positive value for neutral atoms indicating that the ionization process is an endothermic process . The closer the outermost shell electrons are to the nucleus of an atom higher is it's ionization energy.It is expressed in electron volts or joules.
Ionization energy increases across period as more energy is required to remove electron from an atom as it is closely held along a period while it is decreasing down the group as on going the group the inter-nuclear distance increases and as a result less energy is required to remove an electron.
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A yellow solid, W is soluble in water. Which method of separation can be used to obtain the solid W from an aqueous solution?
A Neutralisation
B Chromatography
С Distillation
D Crystallisation
which professional most likely uses x-ray technology a financial analyst or a dentist
Answer:
A dentist
Explanation:
Hope this helps
asap help for brainlist
Which pair of atoms will form a covalent bond?
Question 7 options:
H and O
Li and I
K and Fl
Na and Cl
Answer:
h and o
Explanation:
because both are non metals
Four preparations involving table sugar (sucrose) are described below. Analyze the sugar preparation processes and the end products.
Sugar Water Sugar Floss Sugar Caramel Rock Sugar
Sugar is added to water, and the water is stirred until the sugar is no longer visible. Sugar is melted and blown with a fan to make thin threads of solid sugar. Pure sugar is melted and cooked until it changes color and becomes a thick, sticky liquid. A highly concentrated solution of sugar water is prepared, large sugar crystals are allowed to form slowly, and then dye is added.
Which of the following is evidence that a chemical reaction has taken place in one of the processes?
A.
the melting and re-solidification of sugar into threads, which are different from sugar’s natural cube-shaped crystals
B.
the slow growth of giant sugar crystals from a highly concentrated sugar-water solution and added dye
C.
the dissolution of solid sugar in water to form a thin, colorless, odorless liquid
D.
the color change that takes place after heat melts and begins to decompose the sugar
Answer:
b
Explanation:
Answer: d:the color change that takes place after heat melts and begins to decompose the sugar
Explanation:i did the study island
T or F: Lone pairs around the oxygen atom of a water molecule play no role in determining its molecular geometry?
Answer:
Explanation:
They play a very important part. The geometry is not a straight line. It is an angle over 90 which means that the molecule has the same general shape as a boomerang. The two hydrogens and the 2 lone electron pairs try to get away as far as possible from each other. The actual shape results in a tetrahedron shape. But the two hydrogens and 1 oxygen actually look like the aforementioned boomerang.
What is the wave length of an electromagnetic radiation ,having a frequency of 5.2 x 10^12 Hz? Note: c= 3.00 x 10^8 m/s
Answer:
[tex] \huge{5.77 \times {10}^{ - 5} m}[/tex]
Explanation:
The wavelength of a wave can be found by using the formula
[tex]\lambda = \frac{c}{f} \\[/tex]
where
c is the speed of the wave
f is the frequency
From the question we have
[tex] \lambda = \frac{3 \times {10}^{8} }{5.2 \times {10}^{ 12} } \\ \\ \\ \\ \large{ = 5.77 \times {10}^{ - 5} m}[/tex]
Hope this helps you
Find the number of CO2 molecules present in 20l of CO2 at 0°C and 772mm of Hg.
I wiLL mark you as brainliest and give 50 points.
Answer:
18
At STP, 22.4 liters of a gas forms one mole that is 6.023×10
23
molecules.
Volume of CO
2
in 1 litre of air =
100
0.03
×1 L
∴ No. of molecules of CO
2
=
22.4
6.023×10
23
×
100
0.03
=8.066×10
18
Explanation:
I guess it's this
[tex]\\ \sf\longmapsto PV=nRT[/tex]
[tex]\\ \sf\longmapsto n=\dfrac{PV}{RT}[/tex]
[tex]\\ \sf\longmapsto n=\dfrac{772(20)}{8.314(273)}[/tex]
[tex]\\ \sf\longmapsto n=\dfrac{15440}{2269.722}[/tex]
[tex]\\ \sf\longmapsto n=6.8mol[/tex]
Unlike solids and liquids, gases can be compressed. How is this physical characteristic of gases beneficial to society?
What is the pH of a 0.02 M HCl solution?
O A
1.7
B.
2.0
3.7
O
D.
4.0
Answer:
2 is answer of this question
How many atoms exist in 100.0 grams of lithium
describe how fluids exert forces on objects
Explanation:
Fluids exert forces on objects because of many molecules of the fluid that continuously collide with the surfaces of the object immersed in the fluid. Squeezing a plastic mustard bottle forces mustard out the top because of the amount of force or pressure applied to it that results in mustard coming out.
When an object is immersed in a fluid, the fluid exerts an upward force known as buoyancy. The buoyant force is caused by the fluid's pressure on the object.
How does fluids exert forces on objects?The upward force exerted by fluids on all matter is known as buoyant force. Force According to Archimedes' principle, the buoyant force on an object in a fluid is an upward force equal to the weight of the fluid that the object replaces or displaces.
A submerged object's buoyant force is equal to the weight of the fluid displaced. By measuring the mass of an irregularly shaped object, this principle can be used to determine its volume and thus density.
Squeezing a plastic mustard bottle forces mustard out the top due to the amount of force or pressure applied to it, which causes mustard to come out.
Thus, Fluids exert forces on objects because their molecules constantly collide with the surfaces of the objects immersed in the fluid.
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predict how phospholipids would arrange if they were placed in a nonpolar solution rather than a polar solution like water.
Answer:
The phospholipids would form a normal bilayer. The phospholipid tails would orient toward the solution, and the heads would cluster away from the solution.
Explanation:
i hope this helps you!
What type of reaction is shown below? Check all that apply. 2Na Cl2 → 2NaCl synthesis decomposition combustion.
Answer:
Synthesis
Explanation:
Trust me on this :)
Chemical properties of water for class 8
Answer:
pH value is 7neither acidic nor basecan be found in all 3 state (ie. liquid, solid and gas {vapour})it's excellent solvent(Help me out )
When a single electron returns to the ground state from an excited state, it emits___
1. A continuous spectrum of all wavelengths of light
2. A line spectrum of 2 or more wavelength of light
3. A single, specific wavelength of light
4. No light
Answer:
3) A single specific wavelength
Explanation:
When an electron returns to ground state, it has to emit a single photon.
When a single electron returns to the ground state from an excited state, it emits a single, specific wavelength of light. Therefore, option 3 is correct.
What is wavelength ?The separation between any two points in a wave and those identical points in the following wave cycle. This can be null-to-null, crest-to-crest, trough-to-trough, etc.
A spectrum is the term used to describe the range of wavelengths or frequencies for wave phenomena. The term was originally used to describe the electromagnetic spectrum, but it is now used to describe the sound spectrum and vibration spectrum.
When electromagnetic radiation such as radio waves, light waves, or infrared waves travel across space, they leave behind distinctive patterns. Each wave has a distinct size and form. Wavelength is the separation between peaks.
Thus, option 3 is correct.
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what is the best way to study and understand electron configuration??
Answer:
You have to remember this memory aid, diagonals and all.
You have to keep a tight tally of the electrons you’ve used so far so you don’t go over the number of electrons in the element you’re working on.
You have to remember how many electrons fit into each subshell (s, p, d, f).
It takes a lot of time, especially when the element has more than 20 electrons.
Explanation:
Short note of modern periodic table
Hi
In the modern periodic table, the elements are arranged in the order of their increasing atomic number. In the modern periodic table, there are seven horizontal rows called periods and eighteen vertical columns (1 to 18) called groups. The arrangement of the periods and groups results in formation of boxes.
Explanation:
If it's help pls give me Brainliest!!
Which ions are isoelectronic with ar?.
Answer:
Isoelectronic means same electronic configuration as Ar. These are such as sulfide ion (S2− ), chloride ion (Cl− ) and phosphide ion (P3− ).
Explanation:
Any atom or ion with 18 electrons is isoelectronic with Ar. Some examples are:
Ca2+S2-Cl-What are isoelectronic?Isoelectronic atoms or ions refer to those that possess an identical number of electrons consequently sharing the same electron configuration. The term "isoelectronic" derives from the Greek words "isos " signifying "equal " and "elektron " denoting "electron".
It is worth noting that isoelectronic atoms or ions may exhibit varying atomic numbers and charges; nonetheless, their electron count remains constant.
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Select the correct answer.
Galileo's pendulum theory stated that the time taken to swing through one complete cycle of a pendulum depends on what?
O A. the mass tied to it
OB
the amplitude of the swing
OC. the length of the string
D the velocity of the pendulum
E.
the volume of the mass tied
Answer:
C. the length of the string
Explanation:
Answer:
C. the length of the string
Explanation:
Which electrophiles can react with an enol?
THE MOLECULE HAS A C=C AND AN -OH GROUP, SO IT IS CALLED AN ENE/OL, I.E., AN ENOL. ENOLS CAN BE FORMED ONLY FROM CARBONYL COMPOUNDS WHICH HAVE ALPHA HYDROGENS. THEY CAN BE FORMED BY ACID OR BASE CATALYSIS, AND ONCE FORMED ARE HIGHLY REACTIVE TOWARD ELECTROPHILES, LIKE BROMINE.
What is the density of an object that has a mass of 149. 8 g and displaces 12. 1 ml of water when placed in a graduated cylinder?.
Answer:
12.38 g/mLExplanation:
The density of a substance can be found by using the formula
[tex]d = \frac{m}{v} \\ [/tex]
m is the mass
v is the volume
From the question
m = 149.8 g
v = 12.1 mL
We have
[tex]d = \frac{149.8}{12.1} = 12.380165... \\ [/tex]
We have the final answer as
12.38 g/mLHope this helps you
(only the rght letter and a explanation you don't really need the explanation ill give brainiest)
What happens when an electrically charged pencil is placed close to water running from a faucet?
A. The pencil attracts the water.
B. The pencil becomes positively charged.
C. The water attracts the pencil.
D. The water repels the pencil.
Answer:
Explanation:
Option c) The water attracts the pencil.
Pencils are though formed of wood that acts as a bad conductor of electricity, quite strangely pencils can be electrically charged.
Here pencils have non-metal carbons present in its graphite tip and this makes the pencils charged.
When this pencil is held near the water of the tap, the hydrogen ions get attracted and thereby the water gets attracted to the pencil.
Water, however, is an excellent conductor of electricity and therefore water and electricity are a dangerous combination.
How many moles are in 9.12 x 1023 molecules of sugar?
Answer:
519
Explanation:
.......................
for each compound in the table below, decide whether there would be any hydrogen-bonding force between molecules of the compound, or between molecules of the compound and molecules of water.
Hydrogen bonding occurs between water and molecules that are polar in nature.
Even though the question is incomplete, I will try to help you to the best of my ability. Hydrogen bonding is formed when hydrogen is bonded to a highly electronegative atom.
Hydrogen bonding could occur between the molecules of a compound or between the molecules of a substance and water. Hydrogen bonding occurs between the molecules of a substances such as NH3, H2O and HF.
On the other hand, hydrogen bonding occurs between water and the compound in compounds such as CH2F2, amines, etc.
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