The melting points of electrovalent compounds are higher than the melting points of covalent compounds. Why?​

Answer:

A scientist measures the standard enthalpy change for the following reaction to be -139.5 kj :

h2(g) + c2h4(g)c2h6(g)

based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of c2h4(g) is _____ kj/mol

Explanation:

Hydrogen ΔHof (kJ/mol) ΔGof (kJ/mol) So (J/mol K)

H2 (g)

0

0

130.7

Carbon ΔHof (kJ/mol) ΔGof (kJ/mol) So (J/mol K)

C2H6 (g)

-84.7

-32.8

229.6

If the candle goes out when a glass jar is placed over it, then oxygen is the limiting reactant.

The limiting reactant is the reactant that is present in the least amount. When the limiting reactant is exhausted, the reaction comes to a halt.

Thus, if the candle goes out when a glass jar is placed over it, then oxygen is the limiting reactant.

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Answer:

Temperature and Volume

Explanation:

PV = n R T

P = n R T / V      pressure depends on the temperature and volume

The pressure of a gas depends on the temperature and volume of the gas.

PV = nRT

Where

From the equation given above, we obtained the following:

PV = nRT

Divide both sides by V

P = nRT / V

R is constant and n = 1

P = T / V

Thus, we can see that the pressure (P) is dependent on the temperature (T) and the volume (V)

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The carbocation stabilized by resonance structure and thereby lowers the energy of the carbocation, hydrogen will add to the carbon in the double bond that produces delocalization of electrons.

A carbocation is a molecule in which a carbon atom has a positive charge and three bonds.

In general, electrons are stabilized by delocalization. The stabilization energy engendered by delocalization over more than two atoms is called the resonance stabilization energy or simply the resonance energy. The greater the extent of electron delocalization the greater the resonance stabilization.

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Answer:

1.54 × 10²⁰ molecules

Explanation:

Dividing the mass by the molar mass, we get the number of moles to be (0.045)/(176.12), which is about 0.0002555 mol.

Avogadro's law states that there are 6.022 × 10²³ molecules in one mole of a substance, so the answer is

(0.0002555)(6.022 × 10²³), which is 1.54 × 10²⁰ molecules.

Explanation:

Hi there!

Chloroethane requires atleast one chlorine in ethane. It's general formula is CnH2n+1Cl. It mean it must have 2 carbons, 5 hydrogens and atleast one chlorine.

In addition, carbon-carbon bond must be single and chlorine is attached to either carbons. The carbon of this compound is SP³ hybridized and has bond angle of 120°.

Hope it helps!

Among the given mediums, Vaccuum is the best thermal insulator to reduce the transfer of thermal energy by radiation as there will be no air particles which carries heat from one place to other. Hence, Option (D) will be the correct option

Heat Radiation refers to the transfer of heat from a hot body to cold body directly, without heating the medium between two bodies.

Vaccum does not have any particles in it. Thus, there will be no transfer of heat through it.

The best example of it is thermous flask in which vaccuum inside thermous flask reduces the transfer of energy through it.

Hence,Among the given mediums, Vaccuum is the best thermal insulator to reduce the transfer of thermal energy by radiation as there will be no air particles which carries heat from one place to other. Thus, Option (D) will be the correct option

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A food processing company might use titration to calculate the precise amount of salt in a particular food stuff.

A process of determining the concentration of a dissolved substance in terms of the smallest amount of reagent of known concentration required to bring about a given effect in reaction with a known volume of the test solution

The general source of error in titration has been;

A food processing company might use titration to calculate the precise amount of salt in a particular food stuff.

It can also be used to determine the concentration of vitamin C or vitamin E additives in foods.

Universal indicator can also work as the indicator in the lab.

When universal indicator is added to a solution, the color change can indicate the approximate pH of the solution.

Acids cause universal indicator solution to change from green toward red whereas, bases cause universal indicator to change from green toward purple.

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Answer:

a.  3.72 [atm]

Explanation:

For a gas at constant temperature, (with no change in number of molecules of the gas), we can apply Boyle's Law:  [tex]P_1V_1=P_2V_2[/tex]

[tex](1.556[atm])(268.5[mL])=P_2(112.4[mL])[/tex]

[tex]\dfrac{(1.556[atm])(268.5[mL\!\!\!\!\!\!\!\!{--}])}{112.4[mL \!\!\!\!\!\!\!\!{--}]}=\dfrac{P_2(112.4[mL]\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!{-----})}{112.4[mL]\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!{-----}}[/tex]

[tex]3.716957[atm]=P_2[/tex]

It seems like the answer should have 4 significant figures since all of the other quantities have 4 significant figures, but the closest answer choice of those provided is a.  3.72

The remaining moles of C is 5.01 moles while the remaining moles of F₂ is 0.

The reaction between carbon and Fluorine is given as;

C + 2F₂  -------> CF₄

1  :    2                1

from the reaction above,

2 moles of F₂ requires 1 mole of C

7.88 mole of  F₂ will require:    7.88/2 = 3.94 moles of C and 3.94 moles of CF₄.

The remaining moles of C = 8.95 - 3.94 = 5.01 moles while the remaining moles of F₂ is 0.

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Answer:

= 7 moles Mno

Explanation:

We have been asked to determine the number of moles required to form MnO.

Mole ratio

Mn : MnO = 1 : 1

The reaction ratio therefore is 1 : 1

Thus 7 moles of Mn react to form 7 moles MnO since we have similar ratio.

Answer:

The answer that I got was 7.0.

Explanation:

It said round to the tenths place so put the .0 after the seven and see if that helps.

Answer:

electromagnetic waves and mechanical waves

Explanation:

I think these two kinds of waves can transmit energy through a vaccume.

Hope I helped!

Electromagnetic waves.

Gravity waves.

The mineral that's illustrated based on the information given will be magnetite.

A mineral simply means any pure substance that has a unique composition and structure.

Since the mineral is black and will stick to you when you walk through the sand at the beach, it's magnetite.

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The earth's mantle will not change in the future because this region is safe from the intervention of human beings.

The transfer of heat and material in the mantle helps us to determine the landscape of Earth. Activity in the mantle moves the plate tectonics, that contributes to volcanoes, seafloor spreading, earthquakes, and building of mountains.

So we can conclude that the earth's mantle will not change in the future because this region is safe from the intervention of human beings.

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Explanation:

c and d. I'm not sure which one is better tho

Nitrogen fixation is the part of the nitrogen cycle where the nitrogen is fixed as nitric oxide. Urea {CON₂H₄} should be added to fertilizer to get the best results. Thus, option B is correct.

Fertilizers are substances that are composed of organic and inorganic compounds that are used to provide nutrients to the plants and crops for growth, development, pest, and insect resistance.

The fertilizers mainly comprise nitrogen, potassium, and phosphorus. Urea {CON₂H₄} has the maximum concentration of nitrogen (46%) and will be the most effective.

The other compound ammonium nitrate {NH₄NO₃} contains 34%, ammonium sulfate { (NH₄)₂SO₄} which comprises 21% of nitrogen by mass, whereas N₂F₂ is not used as a fertilizer.

Therefore, option B. Urea {CON₂H₄} is best to use as fertilizer.

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Answer: A

Explanation:

9 protons correspond to fluorine.

Answer:

Its main advantage is they information fits on one line of text (thus works well when using the formula in paragraphs). Disadvantages are they can be confusing for larger molecules

hope this helps :3

One of the postulates in John Dalton's atomic theory was later subjected to change was that Various scientists found that atoms consist of subatomic particles with varying mass and charge. option C is correct.

An atom is consist of three sub atomic particles called proton, neutrons and electrons also known as the fundamental nit of an atom.

Atom consist of an nucleus into which proton and neutrons are present and protons are positively charged whereas neutrons are neutral and electrons revolve around the nucleus in the fixed paths called shells and negatively charged.

Therefore, the postulates in John Dalton's atomic theory was later subjected to change was that Various scientists found that atoms consist of subatomic particles with varying mass and charge. option C is correct.

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Answer:

D. some scientists found that bonds between atoms are broken rearranged or reformed during reactions. According to Dalton's other theories, this is the only one that differentiates from his original theories :)

Explanation:

The moderately reactive atoms located in the periodic table are fluorine, chlorine, bromine, and iodine which means the halogens family.

The number of balance electrons of the light metals compared to those heavier by listing elements in the order of increasing atomic number.

They are the five non-metals in family 7A of the periodic table. Halogens are chemical elements that form inorganic salts. In the periodic table they are part of group 17 or family 7A.

Halogens are strong oxidants and react mainly with alkali metals (Family I A) which tend to donate an electron. They also react with metals and noble gases (Family VIII A).

The chemical elements are arranged from left to right and top to bottom in order of increasing atomic number, or the number of protons in an atom's nucleus, which generally coincides with increasing atomic mass.

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What are halogen metals?

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A closer look at the triple beam balance shows that mass of the body is 52.5 g.

The term triple beam balance refers to an equipment that is used to determine the mass of an object. It has three different degrees of calibration as shown.

In this case, if we look at the beam balance well, we can see that the mass of the body is 52.5 g.

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The two dark vertical lines in the spectrum shows that all wavelengths except those two cause an electron to move to a lower energy level. Hence, Option (D) is correct

A spectrum of electromagnetic radiation transmitted through a substance, showing dark lines or bands due to absorption at specific wavelengths.

The given fact is explained by the energy levels that electrons may be in are quantized, or vary by a specific amount.

When electrons go from one energy level to another, the difference in those energy level is a specific value, and not a range of values.

If they are transitioning upwards towards a higher energy, they will absorb the photons corresponding to the wavelength of light which has the specific amount of energy they need to ascend, resulting in dark lines.

Similarly, when the electrons transition from higher to lower energy, the same specific amount of energy is released and the emission spectrum shows lines in the places where the absorption spectrum was dark.

Hence, The two dark vertical lines in the spectrum shows that all wavelengths except those two cause an electron to move to a lower energy level. Therefore, Option (D) is correct

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Answer:

If an insufficient amount of nitrogen were produced, the air bag would under inflate and not provide adequate protection. Clearly, the stoichiometry of the reaction is very important.

SF₆

Molar mass: 146.06 g/mol

mole = 25 : 146.06 = 0.171

molecules:

=0.171 x 6.02 x 10²³

=1.03 x 10²³

The subshell that contains the valence electron for sodium is the s subshell

Valence electrons are the electrons located at the outermost shell of an atom

From the question, we are to determine the subshell that contains the valence electron(s) for sodium

The given electronic configuration for sodium is

1s²2s²2p⁶3s¹

The valence electron is the electron in the 3s orbital.

Hence, the subshell that contains the valence electron for sodium is s subshell

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Answer:

27 gm

Explanation:

Well..... the volume of the copper is   3 cm^3

9.0  g/cm^3    * 3 cm^3 = 27 gm

Answer:

37 Degrees Celsius

Explanation:

The enthalpy of combustion of 1 mole of acetylene for the reaction using the information in the table (attached as figure) is - 1,256 kJ/mol

The enthalpy of combustion of a substance is defined as the heat energy given out when one mole of a substance burns completely in oxygen.

Hence, The enthalpy of combustion of 1 mole of acetylene for the reaction using the information in the table is - 1,256 kJ/mol

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