Answer:
3 methylheptane
Explanation:
just toke the test
Gerontology is the scientific study of aging involving various disciplines. It encompasses the understanding of primary and secondary aging phenomena. Specialized fields such as Social Gerontology and Thanatology are also part of this study.
Explanation:The scientific study of the process and phenomena of aging is called Gerontology. Gerontology is a multidisciplinary field, involving medical and biological scientists, social scientists, and economic scholars. It probes the process of aging and the complications faced as individuals grow older.
As aging affects every aspect of human life, biological, social, and psychological, gerontologists aim to understand what it is like to be an older adult in society. The study includes two types of aging- primary aging, which involves inherent biological factors such as molecular and cellular changes, and secondary aging, which is influenced by controllable factors like exercise and diet.
Gerontology also encompasses the specialized field of Social Gerontology, examining the sociological aspects of aging, and Thanatology, the systematic study of death and dying. Scholars in this field also focus on the impact of societal attitudes and beliefs about the aging process.
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The following diagram represents the potential energy for the reaction:
The curves represent two possible reaction paths for the decomposition of ammonia, NH3. One can correctly conclude from the graph that the best explanation for the difference between (I) and (II) is that:
The concentration of NH3 was increased.
The temperature was increased.
The N2 was removed as soon as it was formed.
A catalyst was added.
Well that big peak in the graph there is called the transition state. The reaction needs to get past this energy hurdle to continue. The difference between these two graphs is that II has a lower energy transition state. Catalysts are known to lower transition states so that's my vote, a catalyst was added.
Answer: A catalyst was added.
Explanation:
Activation energy is the extra energy that must be supplied to reactants in order to cross the energy barrier and thus convert to products.
When a catalyst is added top a reaction, it increases the rate of a reaction by taking the reaction through a different path which involves lower activation energy and thus more molecules can cross the energy barrier and convert to products.
The concentration of reactants and products remain same even after addition of catalyst.
B represents activation energy for uncatalyzed reaction and E represents activation energy for catalyzed reaction.
The reaction 2 no(g) + cl2(g) → 2 nocl(g) is carried out in a closed vessel. if the partial pressure of no is decreasing at a rate of 184 torr/min, what is the rate of change of the total pressure in the vessel? the sign of the answer is important.
Answer:
92.0 torr/min.
Explanation:
For the reaction: 2NO(g) + Cl₂(g) → 2NOCl(g).∵ The rate of the reaction = - 1/2(ΔP)NO/Δt = - (ΔP)Cl₂/Δt = 1/2(ΔP)NOCl/Δt.
∵ (ΔP)NO/Δt = - 184 torr/min.
∴ The rate of change of the total pressure in the vessel = - 1/2(ΔP)NO/Δt = (- 1/2)(- 184 torr/min) = 92.0 torr/min.
3. Predict whether each of the following molecules is polar or non-polar: a) IF, b) CS2, c) SO3, d) PCl3, e) SF6, f) IF5
a) IF = polar
b) CS2 = non-polar
c) SO3 = non-polar
d) PCl3 = polar
e) SF6 = non-polar (bonds are polar, but the molecule is non-polar, since the net dipole moment is zero)
f) IF5 = polar
The classification of the given molecules as polar or non-polar are;
a) IF; Polar
a) IF; Polarb) CS2; Non - polar
a) IF; Polarb) CS2; Non - polar c) SO3; Non - polar
a) IF; Polarb) CS2; Non - polar c) SO3; Non - polar d) PCl3; Polar
a) IF; Polarb) CS2; Non - polar c) SO3; Non - polar d) PCl3; Polare) SF6; Non - polar
a) IF; Polarb) CS2; Non - polar c) SO3; Non - polar d) PCl3; Polare) SF6; Non - polar f) IF5; Polar
To answer this question, we need to first understand polar and non - polar molecules.
When we say that a molecule is polar, it means that the arrangement of the atoms is in such a manner that makes one end of the molecule to have a positive electrical charge with the other end having a negative charge. This means that polar molecules are formed from polar covalent bonding when two atoms do not share electrons equally .
When we sat that a molecule is non-polar, what it means is that it does not have electrical poles. This means that it's electrons are shared equally unlike that of polar molecules.
In contrast to polar molecules, non-polar molecules do not have an abundance of charges at the opposite ends. Examples are found in hydrocarbon liquids.
From the Explanations above, we can categorize the given molecules into polar or non polar as;
a) IF; Polar
b) CS2; Non - polar
c) SO3; Non - polar
d) PCl3; Polar
e) SF6; Non - polar
f) IF5; Polar
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It takes the Earth _______ to complete one revolution around the Sun. A. One year B. One day C. One month D. One hour
It'll take one year for the Earth to complete one revolution around the Sun.
How long does it take for the Earth to revolve around the Sun?
AnswerYour answer is (A. One Year) or 365.25 days.
Hope this helps! :D
Enzymes catalyze reaction by stabilizing the _________. If the enzyme binds to the substrate too well, the activation energy for the catalyzed reaction _________. Thus, the enzyme binds best to the _________, and the activation energy _________.
by photosynthesis make it enzymes
Answer:
Transition state, decreases, substrates & gets decreased.
Explanation:
Most of the chemical reactions are slow because of the transition state barriers. It requires a lot of energy to cross the transition state barriers. So enzymes provide an alternate pathway for carrying out the reaction by stabilizing the transition state. When enzymes interact with the substrates with the help of functional groups present in their active sites it results in the lowering of activation energy because the transition state gets stabilized with the help of enzyme.
Explain how fossils can give information about past environmental conditions. Give at least two examples. Answer using complete sentences.
Fossils are vital for understanding past environments, indicating past climates and geological events through their preservation conditions. Index fossils help correlate rock layers, while stable isotopes and molecular clocks provide details on the environment and evolutionary relationships.
Fossils provide valuable information about past environmental conditions due to their unique nature as the remains or impressions of ancient life forms. As organisms are fossilized, they can offer clues about the climate, geography, and biological interactions of their time.
Examples of Environmental Clues from Fossils
Fossils and Past Climates: Certain fossils, such as those of tropical plant species, indicate the region once had a warm climate. Conversely, fossils of organisms known to live in colder conditions suggest cooler climates in the past.Fossils and Geological Events: The presence of marine fossils on mountain tops indicates that the mountains were once under the sea, demonstrating geological uplift and plate tectonics.The conditions required for fossilization - such as rapid burial and lack of oxygen - help explain why fossils are rare. When these specific conditions are met, organisms can be preserved in various forms like petrifications, molds, casts, or even preserved traces like footprints.
Index fossils, which are fossils of organisms that were geographically widespread but limited to a short span of geologic time, are particularly useful in correlating rock layers and understanding the history of life on Earth.
Utilizing Fossil Data
By analyzing stable isotopes found in fossils or employing relative and absolute dating methods, scientists can reconstruct past environments and understand the broader ecological context. Molecular clocks, which compare genetic differences to estimate the times when different species diverged, help clarify evolutionary relationships, offering a more complete picture of life's history. However, 'carbon dating' is only applicable for dating relatively recent fossils, as the half-life of carbon-14 is about 5,730 years, which limits its utility for much older specimens.
Data: Beaker Test 1:Temp/VolBeaker Test 2:Temp/VolBeaker Test 3:Temp/VolBeaker Test 4:Temp/VolBeaker Test 5:Temp/VolTrial One: Air-14.5 °C / 4.3 mL0.9 °C / 4.7 mL21.7°C / 5.0 mL48.5 °C / 5.4 mL81.2 °C / 5.9 mLTrial Two: Nitrogen (N2)-14.5 °C / 4.4 mL0.9 °C / 4.7 mL21.7 °C / 5.1 mL48.5 °C / 5.4 mL81.2 °C / 5.9 mLData Analysis: Create a separate graph of temperature vs. volume for each of the gas samples. You are encouraged to use graphing software or online tools to create the graphs; be sure to take screenshots of the graphs that also include your data.Make sure to include the following on your graphs:•Title•Labels for axes and appropriate scales•Clearly plotted data points
How much energy, in calories, is required to change a 25.00g of ice at -10.00C to water at 35.00C?
The number placed in front of a compound to balance a chemical reaction is called
Answer: The number placed in front of a compound to balance a chemical reaction is called coefficient.
Explanation:
Assume this general form for a chemical equation:
aA + bB → cC + dDThe letters a, b, c, and d, in front of each compound A, B, C, and D, are called coefficients and indicate the number of formula units (molecules or ions) that take part in the equation.
Those coefficients are needed to balance the equation and ensure compliance with the law of mass conservation.
This example shows it:
Word equation: hydrogen + oxygen yields waterChemical equation: H₂ (g) + O₂(g) → H₂O(g)Balance, adding the coefficients so that the number of each kind of atoms is the same on the left and the right of the chemical equation:H₂ (g) + 2O₂(g) → 2H₂O(g)
In that equation:
The coefficient of H₂ (g) on the left is 1 (it is not written)The coefficient of O₂(g) on the left is 2The coefficient of H₂O(g) on the right is 2
You read it as: 1 mole of gaseous hydrogen and 2 moles of gaseous oxygen yield 2 moles of water vapor.
Determine the formula unit for the compound formed when each pairs of ions interact.
The formula unit for the compound formed when each pairs of ions interact are as mentioned below-
Li⁺ and 0²⁻ forms Li2O
Mg²⁺ and S²⁻ forms Mg S
A1³⁺ and CI⁻ forms AlCl3Na⁺ and
N³⁻ forms Na3N
What do you mean by the formula unit of the compound?The formula unit is the smallest unit of an ionic substance that tells us of the ratio in which ions are combined in the ionic compound.
The formula unit for the compounds formed depends on the valency of the combining ions.
Usually, the formula unit is written on the valency of the ions.
The formula unit for the compound formed when each pairs of ions interact are therefore as written-
Li⁺ 0²⁻ forms Li2O
Mg²⁺S²⁻ forms Mg S
A1⁺³ CI⁻ forms AlCl3 and
Na+ N³⁻ forms Na3N.
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What structural formula represents 4 electrons shared between two atoms
A.0=0
B.S8
C.P4
D.N=N
I think it’s D. I’m not really shore....
the answer is A 0=0
If someone adds thousands of small fish to a lake how would the number or big fish change?
Answer:
The number of large fish will increase.
Explanation:
If in a particular lake, thousands of small fishes are added, then the number of the larger fishes will increase. The reason for this is because in general the larger fishes are feeding on the smaller fishes, thus with the introduction of the thousands of small fishes there will be an increase in their food source. Also, the smaller fishes have much quicker reproduction, so the chances are that they will reproduce quickly enough so that they increase in numbers, thus providing constant food source that will enable the support of larger populations of the larger fishes.
Great change occur in big fish population with the introduction of thousands of small fish.
If someone adds thousands of small fish to a lake the number of big fish increases if their food is these small fishes because more food is available for it which results in the increase of population of big fish.
While on the other hand, if the small fishes feed on the same food on which the big fish feed than there is competition which negatively affected the big fish and decrease in population due to unavailability of food so we can conclude that big change occur in big fish population with the introduction of thousands of small fish.
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Why does Earth rotate?
1. Because Earth is formed from cold gases collapsing due to gravity
2.Because the matter in the nebula that formed Earth was spinning
3.Because Earth forms more than 99% of the mass of the solar system
4.Because the hydrogen atoms inside the nebula fused to form helium
The answer would actually be, because Earth is formed from cold gases collapsing due to gravity. The Solar System was formed when a huge amount of dust and gas began to collapse under its own gravity, and as the cloud collapse it started to spin causing the material within the cloud to gather into a swirl and then formed into planets and as the planets are formed they kept this spinning motion.
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What is the molarity if a solution that contains 289 grams of sugar in a 2 liter solution?? Molar mass of source is 342.2965g/mol
Answer;
= 0.422 M
Explanation;Molarity or concentration is the number of moles of a solute in 1 liter of a solution.
Therefore; Molarity = n/V ; where n is the number of moles and V is the volume of the solution in L.
Number of moles = Mass/molar mass
= 289 g/342.2965g/mol
= 0.844 Moles
Therefore;
Molarity = 0.844 moles/ 2L
= 0.422 M
At a certain temperature, the equilibrium constant, kc, for this reaction is 53.3. h2(g)+i2(g)â½âââ2hi(g)kc=53.3 at this temperature, 0.700 mol of h2 and 0.700 mol of i2 were placed in a 1.00-l container to react. what concentration of hi is present at equilibrium?
Answer:
Explanation:
5.11= 9.3001x
x=0.5494
2 mol HI produced. Thus,
(2)(0.5494)=1.0989 = 1.09 = [HI] present at equilibrium.
A solution containing which one of the following pairs of substances will be a buffer solution?
A) RbCl, HCl
B) KBr, HBr
C) CsF, HF
D) NaI, HI
E) none of the above
Answer:
C) CsF, HF
Explanation:
A buffer is a solution that resists change in PH. It usually has a weak acid, and a base. In this case; CsF , HF would make a buffer solution such that; HF is a weak acid and F- is its conjugate baseA solution containing CsF and HF pairs of substances will be a buffer solution.
What are buffer solution?Buffer solutions are formed by the mixture of weak acid and its conjugate base or by weak base and its conjugate acid, and helps to retain the pH of the solution if any strong acid or base is added in small quantity.
Among the given pairs all pairs will form buffer solution except CsF and HF, because HF is a weak base and F⁻ is conjugate base of HF acid.
Hence, option (c) is correct i.e. CsF and HF.
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What gas is released when potassium permanganate is decomposed
Potassium permanganate will decompose into potassium manganate, manganese dioxide and oxygen gas: 2KMnO4 → K2MnO4 + MnO2 + O. When Potassium permanganate is heated it turns to Potassium manganate, manganese dioxide and oxygen gas
When potassium permanganate is decomposed, oxygen gas is released.
Potassium permanganate can be thermally decomposed according to the following equation:
[tex]2KMnO_4 --->K_2MnO_4+MnO_2+O_2[/tex]
The products formed are potassium manganate (K2MnO4), Manganese dioxide (MnO2), and oxygen (O2). Out of all the products, the only one that is gas is O2.
If the reaction is carried out in an open chamber, the oxygen gas would be released.
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Why do you think some of the indicators used in experiment 2 were different than the ones used in experiment?
Must show work for questions. Please also explain, I don't understand.
11. The heat combustion of acetylene, C2H2 (g), at 25°C, is -1299 kJ/mol. At this temperature, ∆H_f° values for CO2(g) and H2O(l) are -393 and -286 kJ/mol, respectively. Calculate ∆H_f° for acetylene.
12. Consider the following data. Use Hess's law to find the change in enthalpy at 25°C for the following equation.
Answer:
11. 227 kJ·mol⁻¹; 12. 587 kJ
Step-by-step explanation:
11. Calculate ΔH°f
The formula for calculating the enthalpy change of a reaction by using the enthalpies of formation of reactants and products is
ΔH°r = ΣmΔH°f(products) - ΣnΔH°f(reactants)
2C₂H₂ + 5O₂ ⟶ 4CO₂ + 2H₂O; ΔH°c = -1299 kJ·mol⁻¹
ΔH°f/kJ·mol⁻¹: 2x 0 -393 -286
2(-1299) = 4(-393) + 2(-286) - 2x
-2598 = -1572 - 572 - 2x
-2598 = -2144 -2x
-454 = -2x
x = 227 kJ·mol⁻¹
ΔH°f for acetylene is 227 kJ·mol⁻¹
12. Hess's Law
Warning: It is almost impossible to solve a problem like this by trial and error. You must have a strategy beforehand.
We have five equations:
(I) Ca + 2C ⟶ CaC₂; ΔH = -62.8 kJ
(II) Ca + ½O₂ ⟶ CaO; ΔH = -635.5 kJ
(III) CaO + H₂O ⟶ Ca(OH)₂; ΔH = -653.1 kJ
(IV) C₂H₂ + ⁵/₂O₂ ⟶ 2CO₂ + H₂O; ΔH = -1300 kJ
(V) C + O₂ ⟶ CO₂; ΔH = -393.51 kJ
From these, we must devise the target equation:
(VI) CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂; ΔH = ?
Here comes the strategy. Remember, you can use each of the given equations only once.
Start with the target equation. It has CaC₂ on the left, so you need an equation containing CaC₂ on the left.
Reverse Equation (I). When you reverse an equation, you change the sign of its ΔH.
(VII) CaC₂ ⟶ Ca + 2C; ΔH = 62.8 kJ
Equation (VII) has Ca on the right, and that is not in the target. You need an equation with Ca on the left to cancel it. Add Equation (II)
(VIII) Ca + O₂ ⟶ CaO; ΔH = -1271.0 kJ
Equation (VII) also has 2C on the right, and there is no C in the target. We need an equation with 2C on the left to cancel it.
Double Equation (V). When you double an equation, you double its ΔH.
(IX) 2C + 2O₂ ⟶ 2CO₂; ΔH = -587.02 kJ
Now, we must eliminate the CaO from Equation (VII). Add Equation (III).
(X) CaO + H₂O ⟶ Ca(OH)₂; ΔH = -653.1 kJ
Equation (VIII) has 2CO₂ on the right. You need an equation with 2CO₂ on the left.
Reverse Equation (IV).
(XI) 2CO₂ +H₂O ⟶ C₂H₂ + ⁵/₂O₂ ; ΔH = 2600 kJ
Now, we add all five equations, cancelling substances that appear on both sides of the reaction arrow. All the formulas in italics have been cancelled
(VII) CaC₂ ⟶ Ca + 2C; ΔH = 62.8 kJ
(VIII) Ca + ½O₂ ⟶ CaO; ΔH = -635.5 kJ
(IX) 2C + 2O₂ ⟶ 2CO₂; ΔH = -787.02 kJ
(X) CaO + H₂O ⟶ Ca(OH)₂; ΔH = -653.1 kJ
(XI) 2CO₂ + H₂O ⟶ C₂H₂ + ⁵/₂O₂ ; ΔH = 2600 kJ
(VI) CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂; ΔH = 587 kJ
ΔH = 587 kJ
Derive the relationship between V1 and V2, the volumes of a gas at two pressures, P1 and P2
Answer:
P₁V₁ = P₂V₂.
Explanation:
Boyle’s Law : At constant temperature, the volume of a given quantity of a gas varies inversely with its pressure.It is clear from the data that V ∝ 1/P.Also, PV = constant.So, for two different values of both P and V:
∴ P₁V₁ = P₂V₂.
If the volume of a confined gas is doubled while the temperature remain constant, what change (if any) would be observed in the pressure
The gas will obey Boyles Law:
P1 V1 = P2 V2 where P1 and V1 are the original pressure and volume and P2 and V2 are the new values.
If V2 = 2V1 (given) then:
P1 V1 = P2 *2 V1
P2 = P1 V1 / 2V1
P2 = P1 / 2
In other words the pressure is halved. (answer).
How fast will a ball be falling after 15 seconds
Answer:
it depends on how high up u dropped the ball if the ball was only taking 15 seconds to hit the ground then the ball couldn't go any faster cause its done landed but if the ball was falling 20 mph then there is a chance that it would go 25mph landing compared to when it first fell
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What are the characteristics of an ideal index fossil species?
An ideal index fossil species should be easily recognizable, abundant, have a brief geologic lifespan, and a wide geographic distribution, assisting in the dating of rock layers.
The characteristics of an ideal index fossil species are that the organism should be easily recognizable, abundant, have existed for a relatively short period of time (geologically speaking), and possess a wide geographic distribution. These criteria make the fossil useful for dating and correlating the age of rock layers. For example, Belemnites, a type of extinct squid, are considered good index fossils of the Mesozoic era because they meet all of these criteria. When these fossils are found in a rock layer, they signal that the rock is from the Mesozoic period, specifically between 252 and 66 million years ago.
What is most misleading about the contour map shown below?
The contour interval is too large to see much detail in the landscape.
The contour interval is too small, making the map hard to read.
The contour interval is inconsistent.
There is nothing wrong with the map.
Answer: The contour interval is inconsistent.
Explanation: I just too the test and this is the correct answer.
Answer:
c
Explanation:
This type of nucleus is formed during a solar nuclear reaction by the fusion of four nuclei.
a helium-4 nucleus is formed
what is the temperature of melting ice? A.) 0 °C B.) less than 0 °C
C.) more than 0 °C D.) there is no way to know for sure without a thermometer
A o degrees Celsiusfycgvhbjhuygftxetrfyguhijuhygutfytftg
If i am correct the answer should be C because less than the amount would mean the ice has to melt from its ice form back to the original water liquid form.
If you were a water molecule in a glass of water how would you best describe your relationship with the water molecules around you? A.) always near the same molecules B.) held in a rigid pattern with other molecules C.) consonantly running into different molecules D.) moving slowly away from some molecules and quickly towards others
Answer: A.) always near the same molecules
Explanation:
The capillary action of water is the movement of water from roots to the leaves and other plant parts against the gravitational force of earth. This conduction of water is facilitated by the two properties of water that are cohesion and adhesion.
Cohesion can be define as the attraction of the molecule of water towards another water molecule. Adhesion can be define as the attraction of the molecules of water towards the different type of molecule.
Among the given options A is the correct option because of the fact that the attraction of water molecules among themselves gives water a definite volume in the glass. Cohesive forces keeps the water molecules close together.
As a water molecule in a glass of water, you are constantly running into different molecules due to the higher kinetic energy in the liquid state which allows free movement, with transient hydrogen bonding creating temporary clusters.
Explanation:In a liquid state, such as being a water molecule in a glass of water, you would experience a dynamic and ever-changing environment. If we imagine ourselves as a water molecule, we would be in constant motion, with hydrogen bonds forming and breaking as we interact with our neighboring molecules. Unlike in a solid where molecules are in a fixed position and only vibrate, in a liquid state, the molecules have more energy allowing them to move around freely, although they are still close to each other. This movement leads to different clusters or ''clumps'' of molecules circulating within the confines of the container.
The correct answer to the given question is C.) constantly running into different molecules. Water molecules in a liquid phase such as in a glass of water are not held in a rigid pattern, nor are they always near the same molecules because their increased kinetic energy allows them to move and trade places with one another. This movement is random yet constrained by the surface of the liquid. The hydrogen bonding that occurs is transient - while it does create some structure, it is not rigid or permanent.
48g LiOH dissolved in 1.0 L of solution. calculate the molarity
How many total moles of ions are released when the following sample dissolves completely in water? 6.188 x 10 21 formula units of NiCl 2 a. 1.36 mol of ions b. 1.86 mol of ions c. 3.08 x 1022 mol of ions d. 0.0205 mol of ions e. 3.08 x 10-2 mol of ions
Answer:
e. 3.08 x 10⁻² mol of ions.
Explanation:
Every 1.0 mole of any compound contains Avogadro's number of molecules (6.022 x 10²³).We can get the no. of moles of NiCl₂ using cross multiplication:1.0 mol NiCl₂ contains → 6.022 x 10²³ molecules.
??? mol NiCl₂ contains → 6.188 x 10²¹ molecules.
∴ The no. of moles of NiCl₂ = (1.0 mol)(6.188 x 10²¹ molecules)/(6.022 x 10²³ molecules) = 1.028 x 10⁻² mol.
NiCl₂ is ionized according to the equation:NiCl₂ → Ni²⁺ + 2Cl⁻.
Which means that every 1.0 mol of NiCl₂ is ionized to produce 3.0 moles (1.0 mol of Ni²⁺ and 2 moles of Cl⁻).
∴ The total moles of ions are released = 3 x 1.028 x 10⁻² mol = 3.083 x 10⁻² mol of ions.
Approximately 0.0309 moles of ions are released when 6.188 x 10^21 formula units of NiCl2 dissolve in water. Hence, the answer would be (e) 3.08 x 10^-2 mol of ions.
Explanation:To calculate the total moles of ions released when 6.188 x 1021 formula units of NiCl2 dissolves in water, we first need to convert the formula units to moles using Avogadro's number (6.022 x 1023 formula units/mole). The number of moles of NiCl2 is therefore around 0.0103 moles.
However, each unit of NiCl2 releases 3 ions (1 Ni2+ and 2 Cl-) when it dissolves. Consequently, the total moles of ions released into the water is approximately 0.0309 moles (0.0103 moles*3 ions/mole). So, the closest answer would be (e) 3.08 x 10-2 mol of ions.
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How many electrons are needed in the outer energy levels of most atoms for the atom to be chemically stable?
Answer: eight (8), for most atoms.
Explanation:
Atoms gain chemical stability by completing the highest energy level with all the electrons it can have, which is 8 for most atoms.
The elements of the first period (row 1), hydrogen and helium, have outer energy level, n, equal to 1.
So, since n = 1, the atoms of hydrogen and helium (in the ground state) fill the 1s orbital, so they need just two electrons to be chemically stable. That is why helium, having 2 electrons, is a noble gas, and hydrogen, having 1 electron, just needs to add 1 more electron to be chemically stable like helium.
For period 2 through 7 of the periodic table (n = 2, n=3, n =4, n =5, n = 6, and n = 7), the outer energy levels can hold 8 electrons. That is why the noble gases Ne, Ar, Kr, Xe, Rn, and Og, each with 8 electrons in the outer energy level are chemically stable.
Here you have two examples to see how this works:
Fluoride, F, has atomic number 9, so it has 9 electrons, two of them are in the energy level 1 and seven are in the energy level 2. Hence, F needs to gain 1 electron to complete 8 and be chemically stable.Sulfur, S, has atomic numberr 16. It has 16 electrons, six of them are in the outer energy level (level 3), and it needs to gain 2 electrons to complete 8 and be chemically stable.