Which solvent was more effective for the recrystallization of naphthalene ethanol or hexane?

Final answer:

Separation of compounds requires chemical methods because of the chemical bonds between elements, while mixtures can be separated through physical methods due to the absence of chemical bonding between components.

Explanation:

The methods for separating compounds and mixtures differ mainly based on the nature of the materials in question. Compounds have definite compositions with chemical bonds between the elements and can only be separated into their elements using chemical methods such as electrolysis. On the other hand, mixtures are physical blends without chemical bonding. They can be separated into their components using physical methods like filtration, distillation, and crystallization. For example, a heterogeneous mixture like salt mixed with pepper can be separated through simple manual methods like sorting, while a homogeneous mixture (solution) like sugar dissolved in water may require distillation to separate the sugar from the water.

A chemist would use the difference method to measure the mass of a liquid by weighing an empty container and then the container with the liquid, and subtracting the two measurements.

A chemist would use the difference method to measure the mass of a liquid by first weighing an empty container, such as a beaker or flask. Then, the liquid is added to the container and the combined mass of the container and liquid is measured. The difference in mass between the two measurements represents the mass of the liquid.

For example, if an empty beaker weighs 50 grams and the beaker with the liquid weighs 75 grams, then the mass of the liquid would be 25 grams (75 grams - 50 grams).

the correct answer is temperature

Answer: The correct answer is temperature.

Explanation:

The solubility is defined as the amount of solute that can be dissolved in a given amount of solvent at specific temperature.

We are given that the solubility of NaCl is 35.9g per 100g at 20°C.

If we dissolve 35.9 grams in 100 grams of water, it is completely dissolve at this temperature.

If the temperature increases, the solubility also increases and if temperature decreases, the solubility decreases.

It is given that some solid remains undissolved, so the temperature would have been decreased, therefore the solubility decreases.

Hence, the correct answer is temperature.

Manganese has a lower electron affinity (EA) compared to its neighbours due to its half-filled d-orbitals. The symmetrical electron distribution in half-filled and fully-filled orbitals have higher stability, hence adding an electron to them is less favorable.

The electron affinity (EA) of an atom is the energy change when an electron is added to a neutral atom to form a negative ion. Manganese, with an atomic number of 25, is located in the middle of the transition metals in the periodic table. In general, elements in the middle of transition series like manganese have a less favorable EA compared to their neighbours. This is because of the half-filled d-orbitals in these elements. For manganese, the electron configuration ends with 3d5 4s2, indicating a half-filled d-subshell.

It's widely recognized that half-filled and fully-filled orbitals have higher stability due to their symmetrical electron distribution. As a result, adding an electron to a half-filled orbital is less favorable, resulting in a lower EA for manganese compared to its neighbours.

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Manganese has a less favorable electron affinity than its neighbors due to its electron configuration and atomic radius.

Manganese (atomic number 25) has a less favorable electron affinity (ea) than its neighbors on either side due to its electron configuration and atomic radius. Manganese has an electron configuration of [Ar]3d54s2, which means it has one less electron than its neighbors.

The atomic radius of manganese is larger than its neighbors, which makes it more difficult for the nucleus to attract additional electrons. This results in a less favorable electron affinity.

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A chemical change is produced as a result of chemical reaction. In physical change material experiences a change in physical properties. The souring of milk is a chemical change.

The chemical change is defined as a process in which there will be the transformation of a substance into a new substance having different composition. Burning of wood, setting of curd, etc. are some examples.

During a chemical change absorption and evolution of energy takes place. Such changes are irreversible in nature. The bonds are broken and new ones will be formed in a chemical change.

When a milk turns sour, the bacteria converts lactose sugar present in the milk into lactic acid. The souring of milk causes the production of sour tasting lactic acid.

Here the original substances present in the milk lose their nature as well as identity. The fermentation is defined as the process in which souring of milk occurs.

Thus the correct option is A.

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When a strontium (Sr) atom loses two electrons, it becomes a cation with a charge of +2.

Here's a step-by-step explanation:

Atomic Number and Electrons: A neutral strontium atom has an atomic number of 38, which means it has 38 protons and 38 electrons.

Losing Electrons: When strontium loses two electrons, it now has 36 electrons (38 original electrons - 2 lost electrons).

Resulting Ion: The atom now has 38 protons (positive charge) and 36 electrons (negative charge), resulting in an overall charge of +2 because there are two more protons than electrons.

Type of Ion: Since it has a positive charge, it is a cation.

Chemical Symbol for the Ion: The symbol for the ion is written as Sr²+.

Therefore, when a strontium atom loses two electrons, it becomes an ion with a charge of +2.

Answer:

B. Ultrasound Technology

Explanation:

e2021

Final answer:

The chemical equation for the reduction step in the formation of silver nanoparticles is Ag+(aq) + e- → Ag(s), demonstrating the reduction of silver ions to solid silver metal.

Explanation:

The question involves writing a chemical equation for the reduction step in the formation of silver nanoparticles. The reduction of silver ions (Ag+) into silver metal (Ag) can be expressed through the following reaction:

Reduction Half-Reaction:

Ag+ (aq) + e- → Ag(s)

This reaction shows the conversion of silver ions in solution to solid silver metal by the addition of electrons, a process known as reduction. In the context of synthesizing silver nanoparticles, this step is crucial as it directly leads to the formation of metallic silver nanoparticles from ionic silver.

The nitryl fluoride molecule (NO2F) exhibits resonance, which means it has multiple Lewis structures with different electron arrangements. The resonance structures for NO2F involve a double bond between nitrogen and oxygen or a single bond between nitrogen and oxygen with a lone pair on nitrogen.

The nitryl fluoride molecule (NO2F) cannot have a single Lewis structure that satisfies the octet rule for nitrogen and has all bonds equivalent. Instead, we use the concept of resonance to represent the actual distribution of electrons. Resonance structures show different arrangements of electrons around the atoms but with the same overall connectivity. Here are the resonance structures for NO2F:

These resonance structures represent the average electronic structure of the nitryl fluoride molecule.

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The total heat required is 37.60 kJ.

To calculate the amount of heat required to convert 59 g of ice at -35°C completely to liquid water at 55°C, we need to consider several steps: heating the ice, melting the ice, and heating the liquid water.

Summing these three quantities gives the total heat required:

Total heat (q total) = q₁ + q₂ + q₃
q total = 4313.15 J + 19706 J + 13584.10 J = 37603.25 J

To convert this into kilojoules (kJ), we divide by 1000:

37.60325 kJ ≈ 37.60 kJ

Therefore, the heat required is 37.60 kJ.

Functional groups attached to a benzene ring can be either electron withdrawing, electron donating, or neither. Electron withdrawing groups deactivate the ring and increase acid strength, while electron donating groups activate the ring and decrease acid strength. Some groups, like alkyl, are neutral with minimal effects.

Effect of Functional Groups on the Benzene Ring:

In order to determine whether a functional group attached to a benzene ring is electron withdrawing, electron donating, or neither, we need to consider both inductive and resonance effects:

Electron Withdrawing Groups:

Functional groups like -NO₂ (nitro), -CF₃ (trifluoromethyl), and -SO₃H (sulfonic acid) are classified as electron withdrawing. These groups deactivate the benzene ring towards electrophilic attack and increase the acidity of benzoic acids. This is due to their ability to pull electron density away from the ring both via inductive effects and resonance.

Electron Donating Groups:

Groups such as -OH (hydroxyl), -NH₂ (amino), and -OCH₃ (methoxy) are electron donating. These substituents activate the benzene ring towards electrophilic attack due to their ability to donate electron density to the ring through resonance, thus decreasing the acidity of benzoic acids.

Neutral Groups:

Some groups, such as alkyl groups (-CH₃), do not have significant electron withdrawing or donating effects. These groups neither significantly activate nor deactivate the benzene ring.

Final answer:

The half-life of the radioactive substance, undergoing decay at a rate of 3.33% per year, is approximately 20.87 years. This means that it takes around 20.87 years for the substance to reduce to half of its initial quantity due to radioactive decay.

Explanation:

Radioactive decay follows an exponential decay model, which can be expressed using the formula:

[tex]\[ N(t) = N_0 \times (1 - r)^t \][/tex]

Where:

[tex]- \( N(t) \)[/tex]is the quantity of the substance at time [tex]\( t \)[/tex],

[tex]- \( N_0 \)[/tex] is the initial quantity,

[tex]- \( r \)[/tex] is the decay rate per unit time, and

[tex]- \( t \)[/tex] is the time elapsed.

In this case, the decay rate [tex](\( r \))[/tex]is given as 3.33%, or 0.0333. To find the half-life [tex](\( T_{\frac{1}{2}} \)), we set \( \frac{N(t)}{N_0} = \frac{1}{2} \)[/tex]and solve for[tex]\( t \)[/tex]:

[tex]\[ \frac{1}{2} = (1 - 0.0333)^t \][/tex]

Taking the natural logarithm of both sides:

[tex]\[ \ln\left(\frac{1}{2}\right) = t \times \ln(1 - 0.0333) \][/tex]

Solving for [tex]\( t \)[/tex] gives us the time required for the substance to decay to half its initial quantity. The result is approximately 20.87 years.

This means that after 20.87 years, the quantity of the radioactive substance will have decreased to half of its initial amount. This exponential decay is a fundamental characteristic of radioactive substances and plays a crucial role in various scientific and practical applications, including the estimation of radioactive waste decay and the determination of the age of archaeological artifacts using radioactive dating techniques.

The answer is 2-Methylpentane. This is irrelevantly known as isohexane, is a branched-chain alkane with the molecular formula C₆H₁₄. It is a important isomer of hexane comprised of a methyl group attached to the second carbon atom in a pentane chain.

The expected major organic product is 4-methyl-2-pentene.

The expected major organic product from the treatment of 4-methyl-2-pentyne with excess hydrogen in the presence of a platinum catalyst is 4-methyl-2-pentene.

Hydrogenation is a reaction in which hydrogen gas is added across a multiple bond. In this case, the triple bond in 4-methyl-2-pentyne is converted to a double bond, resulting in the formation of 4-methyl-2-pentene.

In 3NaOH, the subscript 3 indicates that there are three moles of NaOH. To determine the number of atoms, consider the individual elements in NaOH, there are 9 atoms in 3 NaOH.

Atoms in a formula refers to the individual chemical elements that are present in a compound or molecule. Each element is represented by its atomic symbol and is indicated by a subscript, which represents the number of atoms of that element in the formula.

The atoms in a formula provide information about the types and quantities of elements that make up a compound. The number of atoms can vary depending on the formula and the stoichiometry of the compound. The arrangement and combination of atoms determine the chemical properties and behavior of the substance.

NaOH consists of one sodium (Na) atom, one oxygen (O) atom, and one hydrogen (H) atom. Therefore, in one molecule of NaOH, there are a total of three atoms (1 Na + 1 O + 1 H).

Number of atoms = Number of moles × Number of atoms per molecule

Number of atoms = 3 × 3 = 9

Therefore, there are 9 atoms in 3NaOH.

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Answer:

The rate increases by a factor of 9.

Explanation:

edge

To find the molarity of potassium chloride in the given sample, calculate the volume of water using the density,then determine the molarity by dividing the number of moles of potassium chloride by the volume of water.

To find the molarity of potassium chloride in the given sample, we need to calculate the number of moles of potassium chloride in 21.0 g of water at a depth of 1.00 x 10^4 m.

We know that 1.071 g/mL is the density of ocean water at that depth. Since we have 21.0 g of water, we can calculate the volume of water using the formula: volume = mass / density.

Once we have the volume of water, we can determine the molarity of potassium chloride by dividing the number of moles of potassium chloride by the volume of water.

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The molarity of potassium chloride in the ocean water sample at a depth of 1.00 x 10⁴ m is approximately 0.135 M.

We used the given sample mass, KCl content, and density to perform the calculation

Calculate the volume of the seawater sample:

Convert the volume to liters:

Determine the mass of KCl in grams:

Calculate the number of moles of KCl:

Calculate the molarity of KCl:

Therefore, the molarity of potassium chloride in the sample is approximately 0.135 M.

Answer:

radios

Explanation:

The completed structure of [tex]{\text{C}}{{\text{H}}_{\text{3}}}{\text{SSC}}{{\text{H}}_{\text{3}}}[/tex] is shown in the attached image.

Further explanation:

Lewis structure:

In covalent molecules, different atoms are bonded to each other and this bonding between these atoms is shown with help of diagrams known as Lewis structures, Lone pairs are also indicated by such structures. These are also known as Lewis dot diagrams, Lewis dot structures or electron dot diagrams.

Lewis structure of [tex]{\mathbf{C}}{{\mathbf{H}}_{\mathbf{3}}}{\mathbf{SSC}}{{\mathbf{H}}_{\mathbf{3}}}[/tex] (Refer to the structure in the attached image):

The total number of valence electrons of [tex]{\text{C}}{{\text{H}}_{\text{3}}}{\text{SSC}}{{\text{H}}_{\text{3}}}[/tex] is calculated as follows:

Total valence electrons = [(2) (Valence electrons of C) + (2) (Valence electrons of S) + (6) (Valence electrons of H)]

[tex]\begin{aligned} {\text{Total valence electrons}}\left( {{\text{TVE}}} \right) &= \left[ {\left( {\text{2}} \right)\left( {\text{4}} \right) + \left( {\text{2}} \right)\left( {\text{6}} \right) + \left( 6 \right)\left( 1 \right)} \right] \\ & = 26 \\ \end{aligned}[/tex]  

In [tex]{\text{C}}{{\text{H}}_{\text{3}}}{\text{SSC}}{{\text{H}}_{\text{3}}}[/tex], the total number of valence electrons is 26. In this molecule, each carbon forms three single bonds with three discrete hydrogen atoms and one single bond with sulfur atoms. So 16 electrons are used up in formation of six C-H bonds and two C-S bonds. Each sulfur atom forms one bond with other sulfur atom so 2 electrons are used up in formation of one S-S bond. Out of 26 total electrons, 18 electrons are utilized in formation of bonds in [tex]{\text{C}}{{\text{H}}_{\text{3}}}{\text{SSC}}{{\text{H}}_{\text{3}}}[/tex] and eight electrons are left unutilized and act as four lone pairs. Since carbon forms four bonds and each hydrogen atom forms one bond, four lone pairs are present on both sulfur atoms.

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Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Molecular structure and chemical bonding

Keywords: Lewis structure, valence electrons, CH3SSCH3, 26, 18, lone pairs, carbon, sulfur, hydrogen, four lone pairs, 2, 16.