Help with number 2

2. Which of the following does not describe a pure substance?
(A)
B
D
Molecules of the same type of atom attracted to each other
Molecules of different types of atoms that are not attracted each
other
Individual atoms of different types repeated to form extended
structures
Individual atoms of the same type connected to form extended
structures

Answer: F

Explanation:

we can prevent soil erosion by reducing the amount of water and blockages that might build water up and erode the soil around farmland/other

Answer:

look the image

Explanation:

Concentration refers to the amount of substance present.

The term concentration refers to the amount of substance present. There are many units that could be used for concentration of a solution. This makes reference easy.

To express the concentration in milligram per liter;

45/1000/1 L = 0.045 mg/L

To express the concentration in molarity;

Number of moles = mass/molar mass = 45.00 g /106 g/mol = 0.42 moles

Molarity = 0.42 moles/1 L = 0.42 M

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The liquid with a mass of 31.1415 g and a volume of 30.13 ml has a density of: 1.033 g/ml

The density formula and the procedure we will use is:

d = m/v

Where:

Information about the problem:

Applying the density formula we get:

d = m/v

d = 31.1415 g/30.13 ml

d = 1.033 g/ml

It is a physical quantity that expresses the ratio of the body mass to the volume it occupies.

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In the bicarbonate buffering system, carbon dioxide and water join to form carbonic acid, which dissociates into hydrogen and bicarbonate.

Bicarbonate is an excellent buffering system because this compound can bind free hydrogen ions (H+) and thus the system avoids sudden changes in the pH of a solution.

In conclusion, in the bicarbonate buffering system, carbon dioxide and water join to form carbonic acid, which dissociates into hydrogen and bicarbonate.

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The equilibrium constant of the second reaction is 2.0 * 10^-3.

Let us recall the the equilibrium constant shows the extent to which reactants are converted into products in a reaction. A large positive value of the equilibrium constant shows that most of the reactants is converted into products.

Now we can see that the second reaction is obtained when the first reaction is halved and inverted. This now means that we can write;

K2 = 1/K1^1/2

K2 = 1/√K1

K2 = 1/(2.5 * 10^5)

K2 = 2.0 * 10^-3

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Freon-12 or dichlorodifluoromethane is a common refrigerant and propellant. 5.69 mg of Freon-12 contains 2.8 × 10¹⁹ molecules and the mass of Cl in Freon-12 is 0.94049 gm.

Freon-12 (CCl₂F₂) is a gas that was used in manufacturing propellants and refrigerants. It is a non-inflammable gas also called dichlorodifluoromethane.

Molar mass of CCl₂F₂ = 1 × 12g/mol + 2 × 35.5g/mol + 2 × 19g/mol = 121g/mol

Molecules in 5.69 mg Freon-12 are calculated as:

5.69 mg × 0.001 gm × 1 mol × 6.02 × 10²³ molecules ÷ 121 gm = 0.0002830 × 10²³ molecules = 2.8 × 10¹⁹ molecules

There are two chlorine atoms in a Freon-12 compound so the mass is calculated as:

(5.69 × 0.001 × 2) ÷ 121 =  0.94049 gm of Cl

Therefore, 0.94049 gm of Cl is present in Freon -12.

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Your question is incomplete, but most probably your full question was, that Freon-12 (CCl₂F₂) is used as a refrigerant in air conditioners and as a propellant in aerosol cans. Calculate the number of molecules of Freon-12 in 5.69 mg of Freon-12. What is the mass of chlorine in 5.69 mg of Freon-12?

The mass of Calcium bromide added in the flask is 29.7 g.

Molarity is defined as the ratio of number of moles od solute to the number of volume of solution in litres.

Molarity = number of moles/ volume

Number of moles = Molarity × volume

Given,

Molarity of Calcium bromide = 0.363 M

Volume of Calcium bromide = 410 mL

= 0.410L

By substituting all the value, we get

Number of moles = 0.363 × 0.410

= 0.148 mol

As we know that,

Molar mass of Calcium bromide = 199.89 g

Mole is defined as the given mass of substance to the molar mass of substance.

Given mass = Moles × Molar mass

= 0.148 × 199.89

= 29.75 g

= 29.7 g (significant digit)

Thus, we calculated that the mass of Calcium bromide added in the flask is 29.7 g.

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DISCLAIMER:

The above question is incomplete. Below is the complete question

A chemist adds 410.0mL of a 0.363 M calcium bromide solution to a reaction flask. calculate the mass in grams of calcium bromide the chemist has added to the flask. round your answer to 3 significant digits.

As the solution turns yellow when re cabbage juice indicator  is added it implies that its base solution so the color of the  solution when hibiscus flower juice added is dark grey to green.

when hibiscus indicator added Anywhere from dark pink to pale pink usually indicates an acid, while dark gray to green colors usually indicate a base.

Dark blue should be the color of  red cabbage indicator. The cabbage indicator's color will shift to red or pink if the solution is an acid, and to green or yellow if the solution is a base. In the event that the test solution is neutral, it will stay purple or blue

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The theoretical yield of bromobenzene in this reaction when 30.0g of benzene reacts with 65.0 g of bromine is: 46.153 %

To solve this problem the theoretical yield formula and the procedure we will use is:

theoretical yield = relation between reactants * 100  

Information about the problem:

Applying the theoretical yield formula we get:

theoretical yield = (30.0g * 1g /65.0 g) * 100

theoretical yield = 46.153 %

In chemistry, the yield of a reaction is the amount of product obtained from the conversion of the reactants in a chemical reaction.

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The amount of heat created or absorbed during a reaction that takes place under a constant amount of pressure is measured by the enthalpy change.

The change in enthalpy that occurs as one mole of a compound is created from its component parts is known as the "heat of formation." The total amount of energy that should be added to or released during a chemical reaction is known as the heat of reaction.

By deducting the total of the standard enthalpies of formation of the reactants from the sum of the standard enthalpies of formation of the reactants and products, one can determine the standard enthalpy change of formation.

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The four fundamental forces in the universe are:

Electromagnetic force

Strong Nuclear force

Weak Nuclear force

Anti-gravitational force

Forces refers to any agent which causes a change in the motion or state of rest of a body.

Forces are also described as push or pull agents that change the motion or position of a body when that are applied to that body.

There are four fundamental forces in the universe and they are given below as follows:

Electromagnetic force:

Strong Nuclear force:

Weak force

Anti-gravitational force

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Answer:

Amino acids, nucleic acids, and nucleobases are key biological nitrogen compounds.

Explanation:

Answer:

amines and amides

Explanation:

If we are talking organic/biochemistry only I would say amines and amides

12.5 grams will be left.

Given:

half life of X= 6 days

Initial amount - 50 kg

Amount left after 3 days = ?

Half life - The period of time needed for anything to go through a process in which half of it participates, for example, the period of time needed for half of a radioactive substance's atoms to disintegrate. It means after half life the element will become half its quantity.

A quantity's half-life (symbol - t1/2) is the amount of time needed for it to decrease to half of its initial value. In nuclear physics, the phrase is frequently used to indicate how rapidly unstable atoms decay radioactively or how long stable atoms last.

According to the question, If half life is 6 days and we start with 50 kg of element, after 6 days it will become 25 kg and after 3 days it will become 12.5 grams .

t¹/₂ = 6 days

Initial amount = 50 kg

After half life = 50/2

                     = 25 kg

∴ After 3 days = 25/ 2

                        = 12.5 kg

Hence, 12.5 kg is left after 3 days.

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The way in which the separation methods for homogeneous and heterogeneous mixtures are compared is as follows: a homogeneous mixture could be separated through distillation, while a heterogeneous mixture could be separated through filtration (option B).

A homogeneous mixture is a type of mixture that is uniform throughout, and has only one phase.

A heterogeneous mixture is that which is separated into different regions or phases that have different compositions or properties.

Both homogeneous and heterogeneous mixtures can easily be separated by physical means, however, since homogeneous mixtures are even in composition, they can be separated by distillation.

Therefore, the way in which the separation methods for homogeneous and heterogeneous mixtures are compared is as follows: a homogeneous mixture could be separated through distillation, while a heterogeneous mixture could be separated through filtration.

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Answer:

A homogeneous mixture can be separated physically, while a heterogeneous mixture can be separated chemically.

Explanation:

The transmission electron microscope (TEM) works much like a light microscope, transmitting a beam of electrons through a thin specimen and then focusing the.

A stream of electrons is sent through a specimen during transmission electron microscopy (TEM), which produces a picture of the sample. The specimen is often a grid- or suspension-supported ultrathin segment that is less than 100 nm thick. As the beam passes through the specimen, a picture is created due to the interaction of the electrons with the material. The picture is subsequently enlarged and focussed onto an imaging device, such as a fluorescent screen, a sheet of photographic film, or a sensor like a scintillator linked to a charge-coupled device.

Due to the electrons' shorter de Broglie wavelength, transmission electron microscopes can image at a resolution that is substantially higher than that of light microscopes.

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question: Using an electron microscope, Jane measured a rod-shaped bacterium and found it to be 0.00000345 meters in length. List the steps she should take to represent this number in scientific notation.

Answer:

The coefficient of this value in scientific notation is 3.45.

The decimal point needs to be moved six places to the right, so the exponent is -6.

0.00000345 = 3.45 × 10-6

Explanation: edmentum sample answer

Elements that have 'full' valence electron shells and are thus stable and unreactive are found at rightmost side of the periodic table.

The electrons in an atom's outermost shell, or energy level, are called valence electrons.

For instance, the valence electrons of oxygen are six, with two in the 2s subshell and four in the 2p subshell.

The noble gases—helium, neon, argon, krypton, xenon, and radon—belong to the group (family) of elements that have complete outer shells.

Element 118, oganesson, also belongs to this group, although almost all of its chemical and physical properties are yet unknown.

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8

The octet rule explains reactivity in relation to valence electrons.

Valence Electrons

Firstly, let's define valence electrons. Across the periodic table, elements can have a wide range of total electrons. However, when discussing reactions, valence electrons are the most important. Electrons arrange themselves according to energy levels. Any electrons that are on the outermost energy level are considered valence electrons. Most valence energy levels, also called valence shells, hold 8 electrons.

Octet Rule

Now that we know what valence electrons are we can use them to determine reactivity. It is important to note that atoms are most stable when their valence shell is full (as supported by Hund's rule). The octet rule explains atoms will always attempt to fill their valence shell in order to become stable. If an atom has only a few valence electrons, then it will attempt to lose its electrons. On the other hand, atoms that almost have a full valence shell will attempt to gain new electrons.

The losing or gaining of electrons occurs during reactions. So, if an atom already has 8 valence electrons then it will not react. It is already stable, so it has no need to lose or gain more electrons.

Exceptions

While the octet rule explains a lot, like all rules in chemistry it has exceptions. The most common exceptions are hydrogen and helium. Due to the size of these atoms their valence shell can only hold 2 electrons. So, these atoms are actually unreactive at 2 valence electrons.

Another exception can be seen with sulfur and xenon. Both of these atoms are hypervalent. This means they can react even if they have 8 valence electrons. However, this exception is less common.

Polar term describes the distribution of charges in a water molecule

In water molecule polar charges are seen and polar means a molecule that has a charge on one side of the molecule that is not cancelled out it has a region of partial charge one end is slightly positive and one end is slightly negative they are generally asymmetric that's why the geometry of water is bent and with an uneven distribution of the electron in the water molecule hydrogen is positive and hydroxide is negative means H⁺OH⁻ that's why water is polar molecule

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Helium has a molecular weight of 4.003. The weight of 2 cubic meters of helium at 1 atmosphere and 20°c is 3.27 N.

Helium is the second element in the periodic table. It is the lightest gas present in the atmosphere.

By the law of pure gas.

PV = nRT

The initial pressure is p = 101. 325 Kpa

Initial volume, v = 2 m

The molecular weight of helium is, 4.003

Initial temperature, T = 20°c, = 293 K

Universal gas constant is R = 8.314\ \rm{kJ/kg-K}

Putting the value in the formula

PV = mRT / M

m = 101. 325 Kpa x 2 x 4.003 / 8.314 x 293 = 0.333 kg.

The weight of helium gas

W = mg

0.333 x 9.81 = 3.27 N

Thus, the weight of 2 cubic meters of helium is 3.27 N.

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As a result, the protein molecule is 315 x 10^-9 metres long.

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The chiral ketone (2R) -2-methyl-1-phenylbutan-1-one is converted into

(2S)-2-methyl-1-phenylbutan-1-one by base‑catalyzed racemization.

The mechanism of base‑catalyzed racemization of the chiral ketone is as above.

Ketone is defined as the organic compounds having C=O as a functional group.

Chiral ketone are those in which the the alkyl group bonded with C=O are same.

Base‑catalyzed racemization is defined as a process in which the optically active compounds which is consist of only one enantiomer are allow to converted into an equal mixture of enantiomers having zero optical activity in the presence of catalyst which is basic in nature.

Racemization rates are mainly dependents on the molecule and conditions some of them are pH and temperature.

Thus, we concluded that the chiral ketone (2R) -2-methyl-1-phenylbutan-1-one is converted into

(2S)-2-methyl-1-phenylbutan-1-one by base‑catalyzed racemization.

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ratio of CH3NH2 to CH3NH2+ is 2.58:1

Use the Henderson Hasselbalch equation pH = pKa + log [salt]/[acid]

first solve for [salt]/[acid]

pKb= -log Kb= 7.72

10.30= 7.72 + log [salt]/[acid]

log [salt]/[acid] = 2.58

[salt]/[acid] = 2.58

So you need 2.58 : 1 for the ratio of CH3NH2 to CH3NH3^+

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When Using a gas tube spectroscopy , it give off a certain color or colors when Electrons which are in the gaseous atoms first starts to get excited, and then they tend to fall back to smaller form of energy levels, thereby emitting light that is of a unique  color in the process.

Isaac Newton through  his experiment in 1666.

Energy often excited if the electrons in the gases tends to move to a higher energy states.

Note that for them to be able to get back to the ground state, electrons need to let off excess energy and this is often done in the form of light. The light is said to have different color in all of the tube because of they have different wavelengths of light that need to be released.

Therefore, When Using a gas tube spectroscopy , it give off a certain color or colors when Electrons which are in the gaseous atoms first starts to get excited, and then they tend to fall back to smaller form of energy levels, thereby emitting light that is of a unique  color in the process.

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The correct answer as to which observation most likely indicates that only a chemical change has taken place would that the change cannot be reversed.

A chemical change is the transformation of one substance into another, the emergence of new compounds with distinct properties, or any combination of these. It happens when two compounds mix to create a new material (synthesis or either decomposes to form more substances)

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Answer:

activation energy

Explanation:

dont really have an explanation but there's an image attached.

Given the conditions for a reaction to be spontaneous under a given set of reaction conditions, the reaction not proceed spontaneously at the given temperature; option A



Spontaneous reactions are reactions that proceed without an input of extra energy as the reaction favors the formation of products under the given reaction conditions.

For spontaneous reactions, free energy change, ΔG is negative and entropy ΔS is positive.

Given the above reaction occurring at the given conditions:

H₂ (g) + Br₂ (g) → 2 HBr(g)

The reaction was carried out at 25 °C.

ΔH is -72 kJmol⁻¹ and ΔS =  - 106 Jmol⁻¹K⁻¹

The reaction is an exothermic reaction at room temperature

The entropy, ΔS of the reaction is negative indicating that the reaction is not spontaneous at that temperature.

Therefore, correct conclusion will be that the reaction is exothermic at the given temperature but will not proceed spontaneously under the given conditions.

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The major factors influencing fusion consist of the required high temperature and high pressure which is not shown in the model and hence becomes one of its limitations.

Two major requirements for fusion are:

1) The energy from the high temperature allows the hydrogen atoms to overcome the electrical attraction between the protons. Temperatures of roughly 100 million Kelvin are necessary for fusion. Hydrogen is not a gas at these temperatures; it is a plasma. The high-energy state of matter known as plasma is one in which all atoms have had their electrons removed and are now free to move about. The sun's massive mass and the compression of that mass in the core caused by gravity allow it to reach these temperatures.

2) The hydrogen atoms are compressed together by high pressure. For Fusion, they need to be within 1x10-15 meters of one another. The sun compresses hydrogen atoms together in its core using gravity and its bulk. We must use strong magnetic fields, potent lasers, and ion beams to force hydrogen atoms together.

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