Consider this combination reaction:
2Mg(s)+O2(g)→2MgO(s) ΔH=−1204 kJ
What is the enthalpy for the decomposition of 1 mole of MgO(s) into Mg(s) and O2(g)?
Consider this combination reaction:
What is the enthalpy for the decomposition of 1 mole of into and ?
-1204 kJ/mol
602 kJ/mol
1204 kJ/mol
-602 kJ/mol

Final answer:

The astronomical unit (AU) is the most appropriate unit to represent the distance between an Earth-orbiting space station and Neptune.

Explanation:

The most appropriate unit of astronomical distance to represent the distance between an Earth-orbiting space station and Neptune is the astronomical unit (AU). The AU is defined as the average distance from Earth to the Sun and is approximately 150 million kilometers or 93 million miles. It provides a convenient scale for measuring distances within our solar system, avoiding the use of very large numbers that would be involved if the kilometer were used instead. When discussing the distance between Neptune and an orbiting space station, it's important to remember that Neptune is about 30 AU from the Sun. This puts it at a vastly greater distance from the orbiting space station than the Moon or even other planets within the inner solar system.

Explanation:

In hot air, molecules have more kinetic energy and due to this they move from one place to another. As a result, there occurs more number of collisions between the molecules. Due to this molecules of hot air tend to rise.

Whereas when air is cold then its molecules are closer to each other. As a result, they do not have enough kinetic energy and they do not move from their initial position.

Hence, cold air sinks because of lack of movement in its molecules.

Hot air is less denser than cold air, which is why hot air rises and cold air sinks.

The invisible gaseous cloud that envelops the Earth and reaches into space is called air. About 78% of it is nitrogen, 21% is oxygen, and the remaining 2% or so is made up of different contaminants, water vapour, carbon dioxide, and other trace gases.

Air molecules move more quickly when it warms near the surface of the Earth or on the first level of a building, producing more space between them and making the air less dense than the cooler air above it. Cooler, more dense air sinks while warmer, less dense air rises. Since cooler air's molecule bonds absorb less energy than hot air's, cooler air is denser and hence heavier.

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Answer:

Two electrons because you need 8 electrons to make a atom stable and selenium has 6 electrons.

Explanation:

The valence of selenium, typically -2, refers to its combining power based on its six valence electrons with the configuration 4s²4p⁴. In compounds, selenium tends to gain two electrons to fill its valence shell.

The valence of selenium is the combining power of an element, especially as measured by the number of hydrogen atoms it can displace or combine with.

Selenium has six valence electrons, as indicated by its valence electron configuration: 4s²4p⁴. This means in the fourth energy level (n = 4 shell), selenium has a total of six electrons that can interact with other atoms to form chemical bonds. The valence of selenium can vary depending on the type of compound it forms; however, it is typically -2, as it often seeks to gain two electrons to fill its valence shell and achieve a stable noble gas configuration.

Answer: d. All of the above are true.

Explanation: Ozone is a protective shield present in earth's stratosphere which absorbs the harmful radiations from the sun and thus keeps a low level of harmful ultraviolet radiation from reaching living organisms.

As the sun rays are absorbed by the ozone layer, not all the sun rays reach the earth's surface and thus the temperature of the earth is also maintained.

The ozone present in the troposphere also called as ground level ozone is harmful as it can trigger a variety of health problems and is formed by reactions of pollutants from vehicular emissions in the presence of sunlight. Thus ozone in stratosphere blocks the sunlight and thus prevents the formation of ground level ozone.

Thus all the statements are true.

[tex]\boxed{2.6264752{\text{ g}}}[/tex] of NO is formed during the given reaction.

Further explanation:

Limiting reagent is the species or reagent in a chemical reaction according to which the amount of product is decided. It is completely consumed in the reaction.

Stoichiometry governs the amount of species present in the reaction by using the relationship between reactants and products.

The given reaction is as follows:

 [tex]{\text{4N}}{{\text{H}}_3} + {\text{5}}{{\text{O}}_2} \to {\text{4NO}} + 6{{\text{H}}_{\text{2}}}{\text{O}}[/tex]

The formula to calculate the moles of the substance is as follows:

[tex]{\text{Moles of substance}} = \dfrac{{{\text{Given mass of substance}}}}{{{\text{Molar mass of substance}}}}[/tex]             ...... (1)                                

Substitute 3.25 g for the given mass and 17.03 g/mol for the molar mass in equation (1) to calculate the moles of [tex]\text{NH}_3[/tex].

 [tex]\begin{aligned}{\text{Moles of N}}{{\text{H}}_3} &= \left( {\frac{{{\text{3}}{\text{.25 g}}}}{{17.03{\text{ g/mol}}}}} \right)\\&= 0.1908{\text{ mol}}\\\end{aligned}[/tex]

Substitute 3.50 g for the given mass and 31.98 g/mol for the molar mass in equation (1) to calculate the moles of [tex]\text{O}_2[/tex].

 [tex]\begin{aligned}{\text{Moles of }}{{\text{O}}_2} &= \left( {\frac{{{\text{3}}{\text{.50 g}}}}{{{\text{31}}{\text{.98 g/mol}}}}} \right)\\&= 0.1094{\text{ mol}}\\\end{aligned}[/tex]

According to the stoichiometry of this reaction, four moles of  reacts with five moles of [tex]\text{O}_2[/tex] to form four moles of NO and six moles of [tex]\text{H}_2\text{O}[/tex].

Calculate the moles of [tex]\text{O}_2[/tex] that react with and 0.1908 moles of [tex]\text{NH}_3[/tex] as follows:

[tex]\begin{aligned}{\text{Amount of }}{{\text{O}}_2} &= \left( {{\text{0}}{\text{.1908 mol N}}{{\text{H}}_3}} \right)\left( {\frac{{{\text{5 mol }}{{\text{O}}_2}}}{{4{\text{ mol N}}{{\text{H}}_3}}}} \right)\\&= 0.2385{\text{ mol }}{{\text{O}}_2}\\\end{aligned}[/tex]  

The above calculations concluded that 0.2385 moles of [tex]\text{O}_2[/tex] are needed to react with 0.1908 moles of [tex]\text{NH}_3[/tex] but only 0.1094 moles of  [tex]\text{O}_2[/tex] are present in the reaction mixture. Therefore, [tex]\text{O}_2[/tex] is present in limited quantity and is a limiting reagent.

Since [tex]\text{O}_2[/tex] comes out to be the limiting reagent, the formation of NO is governed by it. According to the reaction stoichiometry, five moles of [tex]\text{O}_2[/tex] produces four moles of NO. Therefore the amount of NO can be calculated as follows:

[tex]\begin{aligned}{\text{Amount of NO}} &= \left( {0.1094{\text{ mol }}{{\text{O}}_2}} \right)\left( {\frac{{4{\text{ mol NO}}}}{{5{\text{ mol }}{{\text{O}}_2}}}} \right)\\&= 0.08752{\text{ mol}}\\\end{aligned}[/tex]

Rearrange equation (1) to calculate the mass of the substance.

[tex]{\text{Mass of substance}}= \left( {{\text{Moles of substance}}} \right)\left( {{\text{Molar mass of substance}}} \right)[/tex]                     ...... (2)

Substitute 0.08752 mol for the moles and 30.01 g/mol for the molar mass in equation (2) to calculate the mass of NO.

 [tex]\begin{aligned}{\text{Mass of NO}} &= \left( {0.08752{\text{ mol}}} \right)\left( {30.01{\text{ g/mol}}} \right)\\&= 2.6264752{\text{ g}}\\\end{aligned}[/tex]

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Answer details:

Grade: Senior School

Chapter: Mole concept

Subject: Chemistry

Keywords: limiting reagent, NH3, NO, H2O, O2, 2.6264752 g, moles, mass, molar mass.

Answer: 65.7 g/mol

Explanation:

To calculate the rate of diffusion of gas, we use Graham's Law.

This law states that the rate of effusion or diffusion of gas is inversely proportional to the square root of the molar mass of the gas. The equation given by this law follows:

[tex]\text{Rate of diffusion}\propto \frac{1}{\sqrt{\text{Molar mass of the gas}}}[/tex]

[tex]\frac{Rate_{X}}{Rate_{CO_2}}=\sqrt{\frac{M_{CO_2}}{M_{X}}}[/tex]

[tex]\frac{83.3}{102}=\sqrt{\frac{44}{M_{X}}[/tex]

Squaring both sides and solving for [tex]M_{X}[/tex]

[tex]M_{X}=65.7g/mol[/tex]

Hence, the molar mas of unknown gas is 65.7 g/mol.

Spoilers in small hybrid cars, SUVs, and sports cars aim to reduce lift and drag and improve the grip of the car on the road. They are crucial for sports cars due to the high speeds involved. However, small hybrid cars and SUVs, contribute more towards aesthetics and fuel efficiency, but the principle of operation remains the same.

Spoilers are used in vehicles, including small hybrid cars and sport utility vehicles (SUVs), as well as sports cars, primarily to reduce lift and drag, and enhance the car's road grip. Generally, spoilers work on the principle of aerodynamics. For sports cars, in particular, the spoiler becomes more significant at high speeds, redirecting air flows to create a downward force that stabilizes the car, enhancing safety during high-speed maneuvers.

Although the purpose is fundamentally the same across all vehicles, the importance of spoilers may vary. In sports cars, with their high-speed indulgence, spoilers are essential components. On the other hand, for small hybrid cars and SUVs, brackets are used more for aesthetic appeal and fuel efficiency. However, the basic function of a spoiler in either scenario remains—to control airflow.

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The sensory receptors are nerve endings or specialized cells able to capture internal or external stimuli, and generate in response nerve impulses.

The answer is: A sensory receptor.

The bond holds together atoms within a molecule is ionic bonds, covalent bonds and metallic bonds.

There are three main types of chemical bonds that hold atoms together within a molecule:

1. Ionic bonds are formed when one atom donates electrons to another atom. The atom that donates electrons becomes a positively charged ion, and the atom that receives electrons becomes a negatively charged ion. The oppositely charged ions are attracted to each other by the electrostatic force.

2. Covalent bonds are formed when two atoms share electrons. The shared electrons are attracted to the nuclei of both atoms, which holds the atoms together. Covalent bonds can be either polar or nonpolar. Polar covalent bonds occur when the atoms share the electrons unequally, while nonpolar covalent bonds occur when the atoms share the electrons equally.

3. Metallic bonds are formed when metal atoms share their valence electrons with each other. The valence electrons form a "sea" of electrons that surrounds the metal atoms. The metal atoms are attracted to the sea of electrons, which holds the atoms together.

The type of bond that holds atoms together in a molecule depends on the elements that make up the molecule and the electronegativity of the atoms. Electronegativity is a measure of how strongly an atom attracts electrons. Atoms with high electronegativity tend to form ionic bonds, while atoms with low electronegativity tend to form covalent bonds.

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Water and ethanol can pass through the membrane even though it's polar because it's a very small molecule and can under go this process through osmosis.

A process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane.

Water can also pass through the cell membrane by osmosis, because of the high osmotic pressure difference between the inside and the outside the cell.

This is not an easy process, because the solubility of water and Ethanol in lipid is about 1 molecule of water per million molecules of lipid.

But, the outside concentration of water or ethanol becomes very high (about 50 mol/L), and the surface area to volume ratio of the cell is very large, so this is an important cellular process.

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Answer:

A - The aluminum can

Explanation:

Aluminum has a lower density than Iron does.

Imagine having a beachball sized ball of both aluminum and iron... The aluminum ball would be nice and light but that iron ball would definitely crush your toes if you dropped it on your foot! Even if they're the same exact size, they have totally different weights.

Yes, Group 2 elements, the alkaline earth metals, lose two electrons to form +2 ions, achieving a noble gas electron configuration, and are typically found as compounds due to their reactivity.

The elements in Group 2 of the periodic table are known as the alkaline earth metals. These elements, which include beryllium, magnesium, calcium, strontium, barium, and radium, have two electrons in their outermost energy level.

In chemical reactions, these Group 2 elements tend to lose two electrons to achieve a noble gas configuration, resulting in a +2 oxidation state. This is because they seek to have a full valence shell, similar to the nearest noble gas in the periodic table.

Group 17 elements (halogens) aim to gain one electron to complete their valence shells, while Group 14 elements have the ability to gain or lose four electrons depending on the context. Group 1 elements, also known as alkali metals, readily lose one electron in chemical reactions.

The chemical reactivity of alkaline earth metals is significant, but not as high as their Group 1 counterparts, due to the higher energy required to remove two electrons. Yet, they are reactive enough that they are not found free in nature, only in compound forms. The reactivity and the +2 oxidation state dominate the chemistry of Group 2 elements.

Phenol rocks 9 sigma (6 C-H, C-O, 2 O-H) and 3 pi bonds (1 C=O, 3 benzene ring).

There are 9 sigma bonds and 3 pi bonds in a phenol molecule.

Here's the step-by-step breakdown:

1. Sigma bonds:

2. Pi bonds:

Therefore, in total, there are 9 sigma bonds (6 from C-H, 1 from C-O, 2 from O-H) and 3 pi bonds (1 from C=O, 3 from benzene ring) in a phenol molecule.

The complete question is here:

How many sigma and pi bonds are there in phenol?

The answer should be Magnesium atoms have 12 protons. This is because the atomic number of an element indicates how many protons there are. Hope this helps someone down the road!

Ammonia is a base! Have a blessed day!

-Steel jelly

Answer:

D.They often have identical cells in series to increase energy output

Explanation:

lol i stg thats the answer just took quiz on edge

Final answer:

The boiling point of water in Mexico City, with an elevation of 7400 ft and an atmospheric pressure of 589 mm Hg, is lower than the sea level boiling point of 100°C. It would be approximately between 90°C and 95°C, although a nomogram or the Clausius-Clapeyron relation would be needed for a precise value.

Explanation:

At higher altitudes, such as Mexico City's elevation of 7400 ft, the atmospheric pressure is significantly lower than at sea level. This decreased pressure results in a lower boiling point of water. While the boiling point of water is 100°C at sea level (760 mm Hg), in Mexico City with an atmospheric pressure of 589 mm Hg, the boiling point is reduced. Based on Table 10.1.4, we can infer that as the altitude increases in places like Mexico City, the boiling point of water decreases. From Table 10.4.1, for example, we notice that at an elevation similar to Mexico City's, the boiling point can be several degrees lower than 100°C. Unfortunately, without the specific data for 589 mm Hg from these tables, we cannot give the exact boiling point temperature, but it would typically be between 90°C and 95°C.

To determine the exact boiling point at a specific altitude and pressure, such as Mexico City's, one would often use a nomogram or a formula derived from the Clausius-Clapeyron relation, which correlates temperature and pressure for the phase change between liquid and gas. To obtain a precise value for Mexico City, it is advisable to consult such a nomogram designed for this purpose.

Electron transitions from higher to lower energy levels cause emission of energy in the form of electromagnetic waves, each with their own specific wavelength. Because the energy levels of elements are quantized, each transition has a specific energy difference. The collection of these transitions makes up the emission spectrum and each spectrum is unique to a specific element, allowing identification.