The idea that the moon, sun, and known planets orbit Earth is called the _______________ model of the universe.

Answer:

much greater

Explanation:

Binding energy of a nucleus is the energy evolved in the formation of a nucleus from free protons and neutrons. It is also defined as the energy that binds nucleons together in the nucleus of an atom.

The nuclear binding energy is far greater than the chemical energy stored in chemical bonds. Nuclear energy is the greatest source of energy which could be exploited to achieve various ends.

Answer:

quantity of heat=mc*theta

=25*0.930(76-25)

=25*0.930*51

=1185.75J

=11.9kJ

Answer:

1.19kJ

Explanation:

The heat can be calculated using the specific heat capacity, mass, and the change in temperature.

q=mxcxΔT=(25.0g)×(0.930Jg⋅∘C)×(76.0−25.0∘C)=1186J

Finally, the heat can be converted from J into kJ using the metric conversion factor.

1186J×1kJ1000J=1.19kJ

Answer:

The answer is: carbon

Explanation:

Organic molecules contain the chemical element carbon (C) in its structure. In this type of molecules, carbon is usually bonded to hydrogen (H), oxygen (O) and, with less frecuency, nitrogen (N). Therefore, in these molecules, carbon forms simple, double and triple bonds with itself. Examples of organic molecules that are very important in biology are carbohydrates, lipids, proteins and nucleic acids.

Answer:

Pressure, P = 15.4 lb/in²

Explanation:

Given that,

Force applied, F = 26.4 lb

Area of cross section, A = 1.71 in²

To find,

Pressure.

Solution,

Pressure is equal to force per unit area of cross section.

[tex]P=\dfrac{F}{A}\\\\P=\dfrac{26.4\ lb}{1.71\ in^2}\\\\P=15.43\ lb/in^2\\\\P=15.43\ Pa[/tex]

Hence, the correct option is (a) "15.4 lb/in²".

Answer:

Communication between scientists increased.

Technological advancements were made.

Explanation:

The options:

Metalworkers began using new metals.

 Communication between scientists increased.

 The American Civil War started.

 Technological advancements were made.

The reasons the number of known elements more than double by 1861 would be because technological advancements have been made and communication between scientists increased.

With the advancement in technology, more equipment become available and research became more sophisticated leading to new discoveries. The new discoveries would not have made much difference if they are not adequately communicated to other scientists.  

Answer:

The reactants should be ethyl bromide and sodium methoxide.

The products of the reactions are diethylether and sodium bromide.  

Explanation:

When ethyl bromide, it reacts with any sodium ethoxide, it gives diethylether and also sodium bromide.

As in the sodium ethoxide, the negatively charged oxygen atom is  very much reactive and it  attacks on the bromine containing a carbon of the ethyl bromide and it replaces it forming methyl ethoxide. This type of reaction is sometimes known as SN2.      

Answer : Option C is correct -- a ketone and an ether

Explanation:

It should be noted that Ketone and ether are the compound on the right that contain two functional groups. an aldehyde and an ether, an aldehyde and an alcohol, a ketone and an ester, and also a carboxylic acid and an ether don't contain two functional groups on the right.

Answer:

burning of paper

melting of lead

Answer:

d- activating a glow stick

Explanation:

Glow sticks produce light through a chemical reaction.

Answer:

a) 1.269 × 10^-7 m

b) This wavelength occurs in the ultraviolet region of the electromagnetic spectrum

Explanation:

The energy required to break the bond= energy of the incident photon

E= 941 × 10^3/6.02 × 10^23 = 1.56 ×10^ -18 J

From

E= hc/λ

h= Plank's constant

c= speed of light

λ= wavelength of incident photon

λ= hc/E

λ= 6.6 ×10^-34 × 3 ×10^8/1.56 ×10^ -18 J

λ= 1.269 × 10^-7 m

b) This wavelength occurs in the ultraviolet region of the electromagnetic spectrum

Answer:

on each side of the salt bridge, which is represented by a double vertical line

Explanation:

While writing a cell notation, the general convention is; anode || cathode. The anode and the cathode are separated by a double line. The anode is written on the lefthand side while the cathode is written on the righthand side.

The cell notation is a shorthand representation of a cell, hence any electrochemical cell can easily be produced based on its cell diagram.

Answer:

C. bucky barnes

Explanation:

i dont know how this relates to chemistry

Answer:

The mass of ascorbic acid in the sample is 0.1076g

Explanation:

In other words to determine ascorbic acid in a sample:

You are adding an amount of I₂. One part is reacting with ascorbic acid and the other with sodium thiosulphate. First, we need to calculate how much thiosulphate reacts to know the iodine that reacts with thiosulphate.

I₂ that reacts with S₂O₃²⁻:

Moles S₂O₃⁻: 0.02030L × (0.196mol / L) = 3.979x10⁻³ moles S₂O₃²⁻.

As 2 moles of S₂O₃²⁻ reacts per moles of I₂, moles of I₂ are:

3.979x10⁻³ moles S₂O₃²⁻ ₓ (1 mole I₂ / 2 moles S₂O₃²⁻) = 1.989x10⁻³ moles I₂

Now, initial amount of I₂ added to the sample is:

0.0500L ₓ (0.0520mol I₂ / L) = 2.600x10⁻³ moles I₂

That means moles of I₂ that react with ascorbic acid = Moles of ascorbic acid are:

2.600x10⁻³ moles I₂ - 1.989x10⁻³ moles I₂ =

6.11x10⁻⁴ moles I₂ = Moles C₆H₈O₆.

To convert moles of substance to mass we need to use molar mass of the substance (176.12g/mol for ascorbic acid):

6.11x10⁻⁴ moles C₆H₈O₆ ₓ (176.12g / mol) =

Answer:

B. Ionic

Explanation:

RbCl is ionic compound formed from the combination of rubidium (a strongly electropositive element) and chlorine (a strongly electronegative element).

The transfer of an electron from rubidium to chlorine leads to the formation of two oppositely charged ions Rb⁺ and Cl⁻.

In a solid crystal of RbCl, the major intermolecular forces of attraction are electrostatic forces of attraction between oppositely charged ions in the molecules of the crystalline solid.

Ion-dipole attraction only occur when the solid is dissolved in a polar molecule like water. Dispersion forces as well as dipole-dipole forces, though present are weak forces and contribute very little to intermolecular attraction. Hydrogen bonding is not present as there are no hydrogen atoms in solid RbCl.

The dominant (strongest) type of intermolecular force present in RbCl(s) is ionic force (Option B).

In conclusion, the dominant (strongest) type of intermolecular force present in RbCl(s) is ionic force (Option B).

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Answer:

90.3 kJ/mol

Explanation:

Let's consider the following thermochemical equation.

2 NO(g) + O₂(g) → 2 NO₂(g)  ∆H°rxn = –114.2 kJ

We can find the standard enthalpy of formation for NO using the following expression.

∆H°rxn = 2 mol × ΔH°f(NO₂(g)) - 2 mol × ΔH°f(NO(g)) - 1 mol × ΔH°f(O₂(g))

∆H°rxn = 2 mol × ΔH°f(NO₂(g)) - 2 mol × ΔH°f(NO(g)) - 1 mol × 0 kJ/mol

∆H°rxn = 2 mol × ΔH°f(NO₂(g)) - 2 mol × ΔH°f(NO(g))

ΔH°f(NO(g)) = (2 mol × ΔH°f(NO₂(g)) - ∆H°rxn) / 2 mol

ΔH°f(NO(g)) = (2 mol × 33.2 kJ/mol + 114.2 kJ) / 2 mol

ΔH°f(NO(g)) = 90.3 kJ/mol

Answer:

The correct answer is b. Negative

Explanation:

An electrolytic cell is based on a reduction- oxidation reaction which is non spontaneous. That means that the standard cell potencial (Eº) is negative. For this reason, an electrical potential must be applied in order to force the reaction. Conversely, a galvanic cell is based on a spontaneous redox reaction, so the galvanic cell produces electrical energy.

⬇️

Explanation:

First convert propane to chloropropane by halogenation reaction in presence of sunlight

CH3-CH2-CH3 + Cl2 → CH3-CH2-CH2Cl + HCl

Chloropropane can be converted into propene by using alcoholic KOH

CH3-CH2-CH2Cl + alc. KOH → CH3-CH=CH2

To convert from Propene to Propan-2-ol, the addition of H2SO4 takes place in accordance with Markovnikov ‘s rule i.e.

The experimental design includes the controlled, independent, and dependent variables. The number of crickets and kinds of containers is two constant. Thus, options A and C are correct.

Control variables are the experimental element that remains fixed and unchanged in an experimental setup. They are constant and not are directly related to the interest of the investigation topic but are known to influence the results and observations.

The control variables can influence the dependent variable of the experiment as the number of crickets in each container and the type of container can indirectly alter the outcome and the conclusion of the experiment. The number of cricket will influence the effect of the temperature and the type of container can alter the survival rate.

Therefore, in options A and C. the number of cricket and container are two constants.

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Answer:

c. 298 K

Explanation:

Nernst equation is an equation used in electrochemistry that relates the reduction potential of a reaction with the standard potential, temperature and concentrations of the reactants in that are been reducted and oxidized. The formula is:

E = E° - RT / nF ln [Red] / [Ox]

Where R is gas constant (8.314J/molK), T is absolute temperature (In Kelvin), n are moles of electrons and F is faraday constant (K/Volt*mol)

In electrochemistry, standard temperature is taken as 298K. That means by assuming standard temperature we can substitute T as:

Answer:

Reactants: K = 2, S = 1, Co = 1, Cl = 2; Products: K = 2, S = 1, Co = 1, Cl = 2

Explanation:

The reaction is a double replacement reaction so the anions (Cl⁻ and S²⁻) switch places.

1 K₂S + 1 CoCl₂ ⇒ 2 KCl +  1 CoS (balanced chemical equation)

On the reactants and products side, K = 2, S = 1, Co = 1, and Cl = 2.

Hope that helps.

Answer:

You'll be left with 0.25 g of phosphorus-32. The nuclear half-life of a radioactive isotope expresses the time needed for a sample of that isotope to reach half of its initial value. In your case, regardless with how much phosphorus-32 you start with, you'll be left with half of that initial mass after 14.0 days.

Explanation:

Answer:

Mixtures can be physically separated by using methods that use differences in physical properties to separate the components of the mixture, such as evaporation, distillation, filtration and chromatography.

Explanation:

You are very much welcom

Answer:

stirring. because it will mixup together

Explanation:

ΔS denotes change in entropy. Entropy is the degree of disorderliness of a system. An increasing ΔS would mean that the entropy of the products is greater than the entropy of the reactants.

Generally the trend of entropy with state of matter is given as;

Gas > Liquid > Solid (Increasing Entropy)

a. H 2O(g) → H 2O(l)

In this reaction, there is a decreasing ΔS, since we are moving from gas to liquid. This would be the last.

b. 2NO(g) → N 2(g) + O 2(g)

There is an increase in gaseous products. This is definitely an increasing ΔS reaction. This would be the first on the list.

C. MgCO 3(s) → MgO(s) + CO2(g)

The products formed are in solid and gaseous state. There is increasing ΔS but not up to reaction 2.

The order is given as;

b. 2NO(g) → N 2(g) + O 2(g)

C. MgCO 3(s) → MgO(s) + CO2(g)

a. H 2O(g) → H 2O(l)

Answer:

The correct answer is option D, that is, magic numbers.

Explanation:

The magic number in nuclear physics refers to the number of nucleons, that is, either neutrons or protons, distinctly, such that their alignment results in the formation of complete shells within the nucleus of the atom. As a consequence, atomic nuclei comprising a magic number of neutrons or protons are much more stable in comparison to other nuclei.  

The seven most broadly known magic numbers are 2,8,20,28,50,85 and 126.  

Answer:

in real-world conditions

Explanation:

Answer:

Ca²⁺ + 2H⁻ + 2(2H⁺ + O²⁻) ----> Ca²⁺ + 2O²⁻ + 2H⁺ + 4H⁰

              (2 electrons lost)    ---->      (2 electrons gained)

Explanation:

The equation of the reaction is as follows: CaH₂ + 2H₂0 —> Ca(OH)₂ + 2H₂

The oxidation numbers of each of the atoms in the molecules are as follows:

In CaH₂, calcium has an oxidation number of +2, while hydrogen has an oxidation number of -1  ; Ca²⁺, 2H⁻

In 2H₂0, hydrogen has an oxidation number of +1 while oxygen has an oxidation number of -2 ; H⁺, O²⁻

In Ca(OH)₂, calcium has an oxidation number of +2 while oxygen has an oxidation number of -2 and hydrogen has an oxidation number of +1 ; Ca²⁺, O²⁻,  2H⁺

In 2H₂, each hydrogen atom has an oxidation number of 0 ; 4 H⁰

Ca²⁺ + 2H⁻ + 2(2H⁺ + O²⁻) ----> Ca²⁺ + 2O²⁻ + 2H⁺ + 4H⁰

On the left hand side, the hydride ion gives up two electrons to become neutral hydrogen atoms.

On the right hand, two hydrogen atoms accept two electrons to form neutral atoms.

These neutral hydrogen atoms pair up to form two hydrogen gas molecules.

Answer:

Bromine.

Explanation:

There is more nuclear charge on bromine because in bromine, there are 35 number of protons and 46 number of neutrons while in selenium, there are 34 number of protons and 45 number of neutrons. The atomic size of selenium is larger because they have lower nuclear charge as compared to bromine and we know that when we go to the left of periodic table atomic size increases which attract the electrons towards itself so the shell comes close to the nucleus and decrease occurs in atomic radius.

Answer:

A. Neutral salts.  (7, 2)

B. Acidic salts.  (4, 6)

C. Basic salts. (1, 3, 5)

Explanation:

We must know where, do the ions come from. If they come from a weak acid or base, they can make hydrolysis in water, so OH⁻ and H⁺ are given to medium.

1. LiF → Li⁺ + F⁻

F⁻  +  H₂O  ⇄  HF + OH⁻

F⁻ can make the hydrolysis, and it gives OH⁻. Salt is basic.

2. SrBr₂ → Sr²⁺  + 2Br⁻

Both are weak and they can not hydrolyse. This salt is neutral.

3. NH₄CN →  NH₄⁺  + CN⁻

Both ions are strong, so they can make the hydrolysis. The thing is, while the ammonium gives protons, the cyanide give hydroxides. To determine how's the salt, we need to compare the Ka and Kb.

NH₄⁺  +  H₂O ⇄  NH₃  +  H₃O⁺   Ka = 5.7×10⁻¹⁰

CN⁻  + H₂O ⇄  HCN  +  OH⁻     Kb = 1.61×10⁻⁵

As  Kb > Ka, pH is basic.

If Ka > Kb, pH would be acidic.

4. NH₄Br →  NH₄  + Br⁻

Br⁻ does not hydrolize. The ammonium cation, reacts in water to give protons to medium that's why the salt will be acidic.

NH₄⁺  +  H₂O ⇄  NH₃  +  H₃O⁺   Ka

5.  KCN →  K⁺  + CN⁻

K⁺ does not hydrolize. The cyanide anion, reacts in water to give hydroxides to medium that's why the salt will be basic.

CN⁻  + H₂O ⇄  HCN  +  OH⁻     Kb

6. NH₄ClO₄ →  NH₄⁺  + ClO₄⁻

ClO₄⁻ comes from the perchlroric acid (a strong acid). It does not hydrolyze

NH₄⁺  +  H₂O ⇄  NH₃  +  H₃O⁺   Ka

Ammonium gives H⁺ to medium so the salt is acidic.

7. LiNO₃ → Li⁺  + NO₃⁻

Both ions does not make hydrolysis. They come from a strong base and a strong acid, so they are the conjugate weak acid and base, respectively.

The salt in this case, will be neutral.

Answer:

C

Explanation:

Atomic radius generally increases as we move down a group and from left to right across a period

Answer:

PO4^3-, HPO4^2-

Explanation:

If an acid gives out a proton, the acid then changes to its corresponding base. Similarly, if a base takes in a proton, it changes to its corresponding acid. If a pair of acid and base differ only by the presence or absence of a proton, then they are referred to as a conjugate acid-base pair.

Let us look at this;

HPO4^2-(aq) ----> H^+(aq) + PO4^3-(aq)

HPO4^2- and PO4^3- differ only in the presence or absence of a proton (H^+) hence they constitute a conjugate acid-base pair.

Answer:

Increase in pressure

Explanation:

The rise in temperature will increase the pressure of the gas.

Answer:

increase is ur answer

hope it helps u

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