Explain physical and chemical change with an example.

Answer:

These are compounds.

Explanation:

As it is formed by chemically bonding of two elements C ( carbon) and H (hydrogen) .

Answer:

Butane and benzene are both compounds. They contain multiple elements bonded together in a specific ratio. Kerosene and gasoline are mixtures because they are combinations of several compounds. Oxygen is an element because it is made up of only one type of atom.

Explanation:

The fossils from the Phanerozoic era are the best preserved due to the following reasons:

These fossils spans from about 541 million years ago to the present day and are considered the best preserved because many organisms developed hard skeletal structures such as shells and bones that are more likely to be preserved as fossils than soft tissue.

Also, the sedimentary rocks are formed by the accumulation and compression of sediment which offer protection and preservation for fossils by preventing decay and erosion. These factors contributed to the high quality and abundance of fossils from the Phanerozoic era.

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Answer:

joules per gram per degree (J/goC) or calories per gram per degree (cal/goC).

Explanation:

Answer:

Joules, Kelvin, or calories

Explanation:

Calcium is an essential metal for the living to provide strength to the bones and teeth and it is necessary for blood clotting. Calcium does not has a role on providing energy to the cells. Hence option a is correct.

Calcium is 20the element in periodic table. It is an alkaline earth metal of second group. Calcium is an abundant mineral present in both living and non-living matters.

Calcium have significant functions in our body. The major function of calcium is that, it is a structural component in teeth and bones. Calcium thus, provides strength to teeth and bones.

Similarly calcium is essential for blood clotting, where calcium acts as a catalyst to convert a protein from its inactive state to active state. Calcium ions are the initiators of responses of nervous tissues to injury . They release free radicals and activate phospholipases.

Calcium ions does not have a known  role in making energy. Hence, option a is correct.

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Answer:

Gas

Explanation:

The question is asking solid, liquid or gas. Gas particles are the smallest.

The molecule that is not a second messenger molecule (D) Steroids.

Steroids are not considered second messenger molecules. Second messengers are intracellular signaling molecules that transmit signals from receptors on the cell surface to target molecules inside the cell, thereby relaying and amplifying the initial signal.

The second messengers mentioned in the options are:

A. cGMP (cyclic guanosine monophosphate)

B. cAMP (cyclic adenosine monophosphate)

C. Calcium

E. Inositol-phospholipid system (which includes molecules such as inositol trisphosphate, diacylglycerol, and phosphatidylinositol)

These molecules are involved in various signal transduction pathways and act as mediators or regulators of cellular responses. However, steroids, such as cortisol or estrogen, are not classified as second messengers.

Steroids typically act as ligands for intracellular receptors, which directly influence gene expression rather than functioning as second messengers within signal transduction cascades.

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Answer: I think this one is the boiling water

sorry if wrong

Explanation:

Answer:

\( \infty \infty \)

The two ways in which humans have negatively affected groundwater are Fertilizers and pesticides.

Fertilizers were chemical substances that are applied to crops in order to boost their yield.

Pesticides are chemicals that are being used to keep pests at bay. Herbicides, insecticides, nematicides, and molluscicides are examples.

Fertilizers and pesticides applied to the land, manure from livestock as well as other animals, landfills, mining operations, even unintended releases such as chemical spills or storage tank leaks are all factors that affect groundwater quality.

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Answer: Diisobutylaluminum hydride (DIBALH) is a reducing agent that can reduce esters to aldehydes or 2' alcohols to ketones. Therefore, the correct answer is (A) ester to aldehyde and (C) 2' alcohol to ketone.

DIBALH is not capable of converting carboxylic acid to ester or ester to a carboxylic acid, nor can it oxidize an aldehyde to a carboxylic acid.

Explanation: Diisobutylaluminum hydride (DIBALH) is a reducing agent that can reduce esters to aldehydes or 2' alcohols to ketones. Therefore, the correct answer is (A) ester to aldehyde and (C) 2' alcohol to ketone.

DIBALH is not capable of converting carboxylic acid to ester or ester to a carboxylic acid, nor can it oxidize an aldehyde to a carboxylic acid.

From this equation, the Pb and H₂O coefficients are 2,2

In the reaction equation, the reaction coefficient is known, which is the number on the left side of the chemical formula. The reaction coefficient serves to multiply the sum of all the atoms in the chemical formula.

The chemical formulas of the reactants are written to the left of the equation and the chemical formulas of the products are written to the right.

                        Pb + H₂O + O₂→ Pb(OH)₂

Number of oxygen atoms on the right = 2

Number of oxygen atoms on the left = 3

To balance the number of oxygens. Change the coefficient of Pb and H₂O to two each:

                     2Pb + 2H₂O + O2 → 2Pb(OH)₂

The coefficient of Pb and H₂O is 2,2

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Answer:

The correct answer is 639 L H₂

Explanation:

We use the ideal gas equation:

We have the following data:

n = 28.3 mol

T= 297 K

P= 1.08 atm

R= 0.082 L.atm/K.mol (gas constant)

We introduce the data in the gas equation to calculate the volume (V):

PV=nRT

⇒V =nRT/P = (28.3 mol x 0.082 L.atm/K.mol x 297 K)/(1.08 atm) = 638.2 L ≅ 639 L

Therefore, the correct option is  639 L H₂

Answer:

639 L H2

Explanation:

took the quiz

ur welcome

The chemical symbols that will complete the equation for the single displacement reaction are:

2NaBr + Cl2 → 2NaCl + \(Br_2\)

This equation represents a chemical reaction between sodium bromide (NaBr) and chlorine gas (Cl2). The reaction produces sodium chloride (NaCl) and bromine gas (Br2).

In this reaction, sodium bromide and chlorine gas are the reactants, while sodium chloride and bromine gas are the products. The numbers in front of each compound or element indicate the stoichiometric coefficients, which represent the relative amounts of each substance involved in the reaction.

The balanced equation shows that for every 2 moles of sodium bromide, 1 mole of chlorine gas is required. This ratio ensures that the reaction proceeds completely and no reactants are left over.

When the reaction takes place, the sodium atoms from sodium bromide combine with the chlorine atoms from chlorine gas to form sodium chloride. At the same time, the bromine atoms from sodium bromide combine to form bromine gas.

This type of reaction is known as a displacement or replacement reaction because the chlorine atoms displace the bromine atoms from sodium bromide, resulting in the formation of new compounds.

Overall, the reaction results in the formation of sodium chloride and bromine gas as the final products. It is important to note that the reaction conditions, such as temperature and pressure, can influence the rate and yield of the reaction.

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Isotopes are any of two or more forms of an element where the atoms have the same number of protons, but a different number of neutrons within their nuclei. Thus, isotopes have the same atomic number but a different mass number.

In an atom, there are three components called subatomic particles as follows:

In a neutral atom, the number of protons, which is the atomic number, equate the number of electrons.

According to this question, the transparent subatomic particle inside the atom's nucleus is proton while the blue colored particle is the neutron.

In atom A, there are 3 protons, hence the atomic number of atom A is 3. However, in atom B, the number of protons and neutrons are 4 and 3 respectively, hence, the mass number i.e. protons + neutrons is 7.

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"The species that would be expected to have the highest concentration in the 0.1 M solution of H₂S is HS⁻ (option c)."

In a 0.1 M solution of hydrogen sulfide (H₂S), the species that would be expected to have the highest concentration depends on the dissociation equilibrium of H₂S. Hydrogen sulfide is a weak diprotic acid, meaning it can donate two protons (H⁺) in separate steps. The dissociation of H₂S can be represented as follows:

H₂S ⇌ H⁺ + HS⁻ (Equation 1)

HS⁻ ⇌ H⁺ + S²⁻ (Equation 2)

To determine which species will have the highest concentration, we need to examine the acid dissociation constants (Ka) for these equilibria.

From Equation 1, the equilibrium constant expression can be written as:

Ka1 = [H⁺][HS⁻] / [H₂S]

From Equation 2, the equilibrium constant expression can be written as:

Ka₂ = [H⁺][S²⁻] / [HS⁻]

In a dilute solution like 0.1 M, we assume that the dissociation of H₂S is incomplete, so we can make the approximation [H₂S] ≈ 0.1 M. Therefore, the concentration of H₂S is approximately constant.

Now, let's consider the pKa values for these equilibria. The pKa1 value for H₂S is approximately 7, and the pKa₂ value for HS⁻ is approximately 14.

Since pKa₁ is lower than pKa₂, it means that the equilibrium represented by Equation 1 is more favorable than the one represented by Equation 2. Thus, at equilibrium, the concentration of HS- will be higher than that of S2-.

Therefore, the species that would be expected to have the highest concentration in the 0.1 M solution of H₂S is HS⁻ (option c).

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The measuring of the concentration of harmful chemicals in the air is more accurate than estimating the amount of harmful chemicals in emissions​ because the molar concentration can be traced up to ppb, ppm levels.

Molar concentration is defined as a measure by which concentration of chemical substances present in a solution are determined. It is defined in particular reference to solute concentration in a solution . Most commonly used unit for molar concentration is moles/liter.

The molar concentration depends on change in volume of the solution which is mainly due to thermal expansion. Molar concentration is calculated by the formula, molar concentration=mass/ molar mass ×1/volume of solution in liters.

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Answer:

1. Na2CO3 + 2HCl --> 2NaCl + CO2 + H2O

2. 2NaOH + H2SO4 --> Na2SO4 + H2O

3. CaCO3 + 2HCl --> CaCl2 + CO2 + H2O

4. 4Na + O2 --> 2Na2O

A paper box without water burns immediately because paper is highly flammable and serves as a fuel source for combustion. On the other hand, a paper box with water can be used as a pot to boil water because the presence of water prevents the box from reaching its ignition temperature and undergoing combustion.

Paper is primarily composed of cellulose fibers, which are highly combustible. When exposed to heat or an ignition source, the cellulose fibers in the paper undergo thermal decomposition, releasing flammable gases and creating a flame. In the absence of any other material that can absorb or dissipate the heat, the flame sustains and consumes the paper box.

However, when water is added to the paper box, it acts as a heat sink and raises the temperature required for the paper to ignite. Water has a high specific heat capacity, meaning it can absorb a significant amount of heat before its temperature increases. As the heat from the flame is transferred to the water, it dissipates and reduces the temperature of the paper box, preventing it from reaching its ignition temperature.

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Answer:

4

Explanation:

If I remember correctly, the atomic # will always be the same as the # of electrons

The approximate bond angle for a molecule with a t-shape molecular geometry is d. 109.5°. This is because the three bonded atoms in this geometry are arranged in a trigonal bipyramidal arrangement, with bond angles of 120° between them.

However, the presence of the two lone pairs of electrons pushes the bonded atoms closer together, reducing the bond angle to 109.5°. This is known as the distorted tetrahedral angle.

The t-shape molecular geometry is a type of molecular shape where there are three bonded atoms and two lone pairs of electrons. This geometry is typically found in molecules such as ClF3. In this geometry, the bond angles between the atoms are not all the same. The two lone pairs of electrons occupy two of the equatorial positions, while the three bonded atoms occupy one equatorial and two axial positions.
It is important to note that the bond angles in a molecule with t-shape molecular geometry may not be exactly 109.5° due to various factors such as lone pair-bonded atom repulsion and bond-bond repulsion. Nonetheless, this value serves as a good approximation for the bond angle in this molecular geometry.

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Answer:

10mm2

Explanation:

I did the test on edg too lol

The solute with a surface area of 10 mm² will dissolve the quickest.

Solubility can be described as the maximum amount of a substance that will dissolve in a given solvent at a temperature. The effects of temperature on solubility can be seen in both solids and gases but the pressure effect is related to the solubility of gases. Surface area is a factor in how slowly or quickly the saturation point will be reached.

The rate of solubility is affected by the surface area of a solid. If we were to increase the surface area of a solute then increase how quickly the solute would dissolve in solution. Even the maximum solubility can be achieved more quickly with greater surface area.

Increasing the surface area will increase the rate of solubility of a solute therefore solute with a surface area of 10 mm² will dissolve the quickest.

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Answer:

bu bir kimya sorusu sanırim

Tetrahedral voids

Octahedral voids

In Part 1 of the question, we are asked to draw the product that results from the provided mechanism arrows. This involves analyzing the reaction steps and understanding the changes that occur during the reaction.

In Part 2, we need to determine whether the elementary step is reversible, meaning if the reaction can proceed in both the forward and reverse directions.

In Part 1, drawing the product resulting from the provided mechanism arrows requires a careful analysis of the reaction steps. The mechanism arrows indicate the movement of electrons and the formation or breaking of bonds. By following the arrows and considering the reactivity of the reactants, we can determine the resulting product(s) of the reaction. It is important to pay attention to the regioselectivity and stereochemistry of the reaction, if applicable.

In Part 2, determining whether the elementary step is reversible involves considering the nature of the reaction and the thermodynamics of the process. Reversible elementary steps involve both forward and reverse reactions occurring under certain conditions. Factors such as energy barriers, equilibrium constants, and reaction conditions influence reversibility. By analyzing these factors, we can determine whether the elementary step is reversible or if the reaction predominantly proceeds in one direction.

Overall, these two parts require a detailed understanding of the reaction mechanism, electron movement, and the factors affecting reversibility to accurately draw the product and determine the reversibility of the elementary step.

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In Part 1, draw the product that results from the mechanism arrows provided. In Part 2, indicate whether the elementary step is reversible. LCH3 4th attempt

Answer:

Its C.

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Answer:

Person above is correct

The answer is C

Explanation:

Answer:

nếu có 40g dung dịch NaOH 20% phairn dùng hết bao nhiêu gam dung dịch HCl 25% để trung hoà

Answer:

It’s eutrophication

Explanation:

There is no way it can be DEFORESTATION or NON  SUSTAINABLE SPECIES

Non sustainable harvesting has something to do with animals and eutrophication means adding excessive nutrients

Answer:A.

Explanation: I took the test, sorry if this is incorrect

Entropy is stated to diminish as a system switches from an ordered to a disordered layout, and vice versa. When randomness rises, ΔS  is positive.

Heat transport (delta Q) divided by temperature equals the change of entropy (delta ΔS ) (T). (Delta Q / T) = delta ΔS  If a physical process can be reversed, the entropy of the environment and the system will stay constant.

One thing to bear in mind when using any one of these equations in computations is that while ΔS  values are typically reported as J/K.mol, G and ΔH values are frequently reported in kJ/mol.

1. 2H30' (aq) + CO23- (aq) - CO2(g) +3H2O(1)

2. CH4(g) + 202,(g) - CO2(g) + 2H2O(l)

3. Mg (s) + Cl2(g) - MgCǐ2(s)

4. SO3(g) + H2O(I) - H2SO4(I)

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The types of chemical bonds present in a mixture of water (water molecules) and oil (triglyceride molecules) are: Hydrogen bonds and van der Waals interactions.

Water molecules are polar and form hydrogen bonds with each other. These hydrogen bonds result from the attraction between the partially positive hydrogen atom of one water molecule and the partially negative oxygen atom of another water molecule.

Oil, on the other hand, primarily consists of nonpolar molecules such as triglycerides. Nonpolar molecules do not form hydrogen bonds but can interact through weak attractive forces known as van der Waals interactions. These interactions occur due to temporary fluctuations in electron distribution, resulting in induced dipoles that attract each other.

Therefore, in the mixture of water and oil, hydrogen bonds form between water molecules, while van der Waals interactions occur between oil molecules and potentially between water and oil molecules.

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