H2O has a Hvap = 40.7 kJ/mol. What is the quantity of heat that is released when 27.9 g of H2O condenses?

The elements with the least chances to attract electrons from the other atoms are group 1 elements. Thus option A is correct.

The elements attract or lose electrons in order to attain a stable configuration. The system has been based on the number of valence electrons in the atom.

The atom with the least electronegativity has the changes to give up the electrons, and the least chance to attract the electrons from the other atoms.

The group 1 elements have 1 valence electrons, and thus have the high chances to give the electron, with the least chances to attract electrons from the other compounds. Thus option A is correct.

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Answer:

The radioactive element will be left at 2 p.m. will be 0.25 g.

Explanation:

Half life of the radioactive element =[tex]t_{\frac{1}{2}}=1 hour[/tex]

Initial concentration of the radioactive element = [tex]N_o[/tex]=1.0 g

Time elapsed = 12:00 pm to 2:00 pm = 2 hours

Concentration of radioactive element left = N

[tex]\lambda =\frac{0.693}{t_{\frac{1}{2}}}=\frac{0.693}{1 hr}=0.693 hr^{-1}[/tex]

[tex]\log N=\log N_o-\frac{\lambda t}{2.303}[/tex]

Putting the given values in the above equation we get:

N = 0.25 gram

The radioactive element will be left at 2 p.m. will be 0.25 g.

Answer: A=2,  B=2 and  C=4

Explanation: Oxygen is the element with atomic number 8 and thus contains 8 electrons which are filled in order of increasing energy levels.

[tex]O:8:1s^22s^22p^4[/tex]

The valence electrons are electrons which are present in the valence shell i.e. the last shell. Thus the valence electrons of Oxygen are in shell 2 in which s orbital contains two electrons and the p orbital contains 4 electrons.

Thus A= 2, B=2 and C=4.

Answer:

The correct number of valance electrons in the electronic configuration of Oxygen is:

A=2, B=2, and C=4

Explanation:

The atomic number of oxygen is 8

The electronic configuration will be,

[tex]\rm O_8\rightarrow1s_2,2s_2,2p_4[/tex]

The electrons present in the outermost shell is called valence electrons.

Hence, in the second shell, the s-orbital contains 2 electrons and the p-orbital contains 4 electrons.

If all the electrons in the outermost shell are removed the first shell becomes a valance shell where 2 electrons are present in the s-orbital.

Therefore correct valence electron configuration is 2,2,4.

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Soaps are made by the process saponification. Soaps contains long chain fatty acids and glycerol. The oily nature of soaps are due the presence of fatty acids.

Saponification is the process, making of soaps from glycerol and fatty acids. Therea are different types of soaps based on the ionic nature of the long chain fatty acids.

There are alkaline soaps in which the acidic chain possess a negatively charged group and acidic soaps are those bearing positively charged ions. The nature of sopas can be varied as per the use also.

Fatty acids are long chain hydrocarbons formed by the combination of simple hydrocarbons and they will reacts easily with alcohols forming esters of fatty acids that are soaps.

Hence, the presence of fatty acids make the soaps oily in nature and move gains friction in our hand.

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Answer: The correct answer is [tex]3.6\times 10^{-6}[/tex]

Explanation:

We are given:

Acid dissociation constant [tex](k_a)=2.8\times 10^{-9}[/tex]

Water dissociation constant [tex](k_w)=1\times 10^{-14}[/tex]

To calculate the base dissociation constant for the conjugate base, we use the equation:

[tex]k_w=k_a\times k_b[/tex]

where,

[tex]k_b[/tex] = base dissociation constant

Putting values in above equation, we get:

[tex]10^{-14}=2.8\times 10^-9}\times k_b\\\\k_b=3.6\times 10^{-6}[/tex]

Hence, the correct answer is [tex]3.6\times 10^{-6}[/tex]

The given reactions are balanced, with the first reaction not requiring any adjustment and the second reaction being balanced as 2CrO42-(aq) + 3N2O(g) → 6Cr3+(aq) + 3NO(g). The oxiding agents are ClO3¯ and CrO42- for the first and second reactions, respectively. The reducing agents are BH4¯ and N2O for the first and second reactions, respectively.

First, it's essential to know that during oxido-reduction reactions, one substance loses electrons (oxidized) and another gains them (reduced). We call the substance oxidized to be the reducing agent and the one reduced to be the oxidizing agent.

For the first reaction BH4¯(aq) + ClO3¯(aq) → H2BO3¯(aq) + Cl¯(aq), there aren't any charges or states of matter to be balanced. Analyzing the oxidation states, the B in BH4¯ goes from -3 to +3, showing it has been oxidized. Thus, BH4¯ is the reducing agent. ClO3¯ reduces to Cl¯, thus ClO3¯ is the oxidizing agent.

Moving on to the second reaction CrO42-(aq) + N2O(g) → Cr3+(aq) + NO(g), balance the equation first by adjusting coefficients to get 2CrO42-(aq) + 3N2O(g) → 6Cr3+(aq) + 3NO(g). This reaction is in an acidic solution, so it's important to note that hydroxide ions do not appear in half-reactions occurring in an acidic solution. SO, in this reaction too, Cr in CrO42- goes from +6 to +3, signifying reduction, making CrO42- the oxidizing agent. N in N2O goes from +1 to +2 which signifies oxidation, marking N2O as the reducing agent.

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The central atom in the ClF4 ion has three nonbonded electron pairs and one bonded electron pair in its valence shell.

The central atom in the ClF4 ion has three nonbonded electron pairs and one bonded electron pair in its valence shell. The Cl atom has a total of seven valence electrons and forms four covalent bonds with the four fluorine atoms. This leaves three lone pairs of electrons around the central Cl atom, which are not involved in bonding.

Electronegativity in water creates partial charges, causing polarity. This polarity allows hydrogen bonding between water molecules, enhancing interactions.

In a water molecule (H₂O), oxygen is more electronegative than hydrogen. This means that oxygen attracts the shared electrons in the O-H bonds more strongly than hydrogen does.

As a result, the electrons spend more time closer to the oxygen atom, giving it a partial negative charge (δ−), while the hydrogen atoms acquire a partial positive charge (δ+). This uneven distribution of charge creates a dipole moment, making water a polar molecule.

The polarity of water molecules causes them to be attracted to each other. The partial positive charge of one water molecule is attracted to the partial negative charge of another, forming hydrogen bonds.

These bonds are relatively weak compared to covalent bonds but are crucial for water’s unique properties, such as its high boiling point and surface tension.

The problem is about diluting a 15% acetic acid solution to a larger volume. After diluting the solution from 250 ml to 500 ml, the new percentage concentration of the acetic acid solution is 7.5%. Hence, the label should read 7.5% acetic acid.

The problem you presented is a typical one in chemistry, which involves the concept of percentage concentration and dilutions. Initially, we have 250 ml of a 15% acetic acid solution. The amount of acetic acid in the solution is therefore 0.15 * 250 = 37.5 g.

The technician adds enough water to the solution to make the total volume 500 ml. However, the amount of acetic acid doesn't change; it remains 37.5g. To find the new percentage of the acetic acid solution, we take the total mass of the acetic acid (37.5g) and divide it by the total volume of the solution (500 ml), then multiply by 100% to get the percentage:

(37.5g / 500ml) * 100% = 7.5%.

So, the label on the solution should say 7.5% acetic acid.

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The correct answers are:

1. B. Mg loses two electrons.

When Mg and Br combine, 2 atoms of Br attaches itself to Mg. The chemical reaction is:

Mg + Br ---> MgBr2

Since Br is more electronegative than Mg, then Mg loses an electron per Br therefore losing 2 electrons.

2. D. An atom that gains electrons must be attracted to an atom that loses electrons.

An ionic bond is formed when one molecule is more electronegative than the other molecule which results in gaining and losing of electrons. The more electronegative molecule gains electron while the less electronegative loses electron.

In the formation of an ionic bond between magnesium and bromine, magnesium loses two electrons to become a Mg₂ + ion, and these oppositely charged ions attract each other to form the bond.

Understanding Ionic Bonds between Magnesium and Bromine:

1. When an ionic bond forms between magnesium (Mg) and bromine (Br), the process involves a transfer of electrons. Specifically, Mg loses two electrons (Option B) to achieve a stable electron configuration similar to the nearest noble gas. As a result, magnesium becomes a Mg₂+ ion.

2. For an ionic bond to form, there must be a transfer of electrons from one atom to another, leading to the formation of ions with opposite charges, which are then attracted to each other (Option D). An atom with a lower electronegativity, like magnesium, will lose electrons and become a positively charged cation. Conversely, an atom with higher electronegativity will gain electrons and become a negatively charged anion, such as bromine becoming Br-.

HCHO2 and NaCHO2, and CH3NH2 and CH3NH3Cl can make buffer solutions. HCl and NaCl, and NH3 and NaOH cannot make buffer solutions.

1. HCHO2 is formic acid, a weak acid, while NaCHO2 is the salt made from the anion of the weak acid (the formate ion [CHO2]). The combination of these two solutes would make a buffer solution.

2. HCl is a strong acid, not a weak acid, so the combination of these two solutes would not make a buffer solution.

3. CH3NH2 is methylamine, which is like NH3 with one of its H atoms substituted with a CH3 group. Because it is not listed in Table 12.8.1, we can assume that it is a weak base. The compound CH3NH3Cl is a salt made from that weak base, so the combination of these two solutes would make a buffer solution.

4. NH3 is a weak base, but NaOH is a strong base. The combination of these two solutes would not make a buffer solution.

This is a problem based on concept of first law of thermodynamics

if a body is giving heat it will be absorbed by some other body or surrounding.

Now we have taken metal at low temperature and water at high temperature

So water will lose some energy and the same amount of energy will be gained by metal. The exchange will continue untill both reach the same temperature.

So answer is

The energy gained by the metal equals the energy lost by the water.

Answer:

Anode

Explanation:

A p e x

The guy that said cathode was wrong :(

The compounds ranked by boiling point from highest to lowest are: Pentane > Isopentane > Neopentane.

The boiling point of a compound is influenced by its intermolecular forces.

Compounds with stronger intermolecular forces tend to have higher boiling points because more energy is required to overcome those forces and convert the substance from a liquid to a gas.

Generally, the strength of intermolecular forces increases with increasing molecular size and surface area.

Pentane is a linear hydrocarbon with five carbon atoms in a row. It has the highest boiling point among the three compounds because it has the greatest molecular size and surface area.

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Answer:

Explanation:

Kinetic energy is the energy possessed by an object by virtue of its motion.

Average kinetic energy is defined as the average of the kinetic energies of all the particles present in a system. It is determined by the equation:

[tex]K=\frac{3nRT}{2}[/tex]

K= kinetic energy

n= number of moles

R= gas constant

T= temperature  

[tex]4265J=\frac{3\times 1\times\times 8.314\times T}{2}[/tex]

[tex]T=342K[/tex]

[tex]tK=(t-273)^0C[/tex]

[tex]T=342K=(342-273)^0C=69^0C[/tex]

Thus temperature will be [tex]69^0C[/tex]

Answer:

c

Explanation:

If a large leak of refrigerant occurs in an enclosed area and no self-contained breathing apparatus is available, the immediate action should be to evacuate the area to fresh air, shut off the source of the leak if possible, and seek medical attention if experiencing symptoms.

If a large leak of refrigerant occurs in an enclosed area and no self-contained breathing apparatus is available, there are several actions that should be taken to ensure safety:

It is important to prioritize personal safety and seek professional assistance when encountering such incidents.

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The energy difference for a transition in the Paschen series from the higher energy shell n=4 is approximately 13.6 eV.

The energy difference for a transition in the Paschen series can be calculated using the equation:

AE = E1 - E2 = 2.179 × 10-18 J

To express the answer in eV, we can use the conversion factor: 1 eV = 1.6022 × 10-19 J

Therefore, the energy difference for the transition in the Paschen series from the higher energy shell n=4 is approximately 13.6 eV.

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To convert 2,150 mmHg to kPa, divide by the conversion factor 7.5 mmHg, resulting in approximately 286 kPa.

A conversion factor is a mathematical ratio that allows you to convert from one unit of measurement to another. It is often used to change units within the same system (e.g., converting inches to centimeters) or between different systems (e.g., converting miles to kilometers) by multiplying or dividing by the appropriate factor.

To convert from millimetres of mercury (mmHg) to kilopascals (kPa), you can use the conversion factor:

1 kPa = 7.5 mmHg

First, divide 2,150 mmHg by the conversion factor:

= 2,150 mmHg / 7.5 mmHg

= 286.67 kPa

Rounding to the nearest hundredth, the answer is approximately 286 kPa.

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The freezing point of the solution is 0.88°C

The melting point of a substance which is also the same as the freezing point is the temperature at which it changes from a solid state to a liquid state at a specific pressure. At the melting point, the substance absorbs heat energy, increasing its temperature and causing the solid structure to break down

We have that;

Number of moles of naphthalene = 10 g/128 g/mol

= 0.078 moles

Mass of benzene = Density * volume

= 0.877 g/cm3 * 100.0 mL

= 87.7 g or 0.0877 Kg

Where;

ΔT = K m i

ΔT = 5.12 *  0.078 moles/ 0.0877 Kg * 1

= 4.6°C

ΔT = Freezing point of pure solvent - Freezing point of solution

Freezing point of solution = 5.48°C - 4.6°C

= 0.88°C

Missing parts

Calculate the freezing point and melting point of a solution containing 10.0 g of naphthalene (C10H8) in 100.0 mL of benzene. Benzene has a density of 0.877 g/cm3

To find the luminous intensity this formula is used;

Luminous intensity = illuminance ×  [tex]radius ^{2}[/tex]

∴ Lv = Ev × [tex] r^{2}[/tex]

We know the luminous intensity is 100 candelas and the illuminance is 4 lux.

∴ 100 = 4 x  [tex] r^{2}[/tex]

∴ 100/4 =  [tex] r^{2}[/tex]

∴ 25 =  [tex] r^{2}[/tex]

∴ r =√25 = 5 meters

Therefore, the surface will be at a distance of 5 meters from the source.

Answer:

5 subshells

Explanation:

Final answer:

To find the limiting reagent between hydrogen and oxygen, we convert their masses to moles and use the stoichiometry of the balanced chemical reaction 2 H2 + O2 → 2 H2O. Oxygen is the limiting reagent because there are not enough moles of O2 to fully react with the available moles of H2.

Explanation:

To determine the limiting reagent when 4.0 g of hydrogen (H2) and 10.0 g of oxygen (O2) are mixed to react according to the equation 2 H2 + O2 → 2 H2O, we need to perform mass-mole calculations for both reactants and compare the stoichiometry of the balanced equation.

First, convert the mass of each reactant to moles:

For H2: Molecular weight is approximately 2.02 g/mol. Thus, 4.0 g H2 ÷ 2.02 g/mol = 1.98 moles of H2.

For O2: Molecular weight is approximately 32.00 g/mol. Thus, 10.0 g O2 ÷ 32.00 g/mol = 0.3125 moles of O2.

According to the balanced equation, 2 moles of H2 react with 1 mole of O2. Therefore, to fully react with 1.98 moles of H2, we would need 0.99 moles of O2. However, we only have 0.3125 moles of O2, which is insufficient to react with all the H2. Therefore, O2 is the limiting reagent.