PLEASE HELP ASAP

Which group tells the three unifying characteristics of chordates?



notochord, gill slits, dorsal nerve cord



dorsal nerve cord, radial symmetry, three layers of cells



water vascular system, backbone, gill slits



exoskeleton, notochord, lungs

ans is A liquid........

Answer:

A.Liquid has no definite shape but does have a definite volume.

Explanation:

Hope it helps

Answer:

O3+, O3, O3-

Explanation:

O3- has the highest bond angle because it has the highest electro negative value. Increase in electronegativity leads to increase in bond angles so as to minimize interelectronic repulsion between the electrons. Decrease in electronegativity leads to decrease in bond angle because the repulsion is minimized.

In general, the more electronegative an ion is, the larger the bond angle. The more electropositive an ion is, the smaller the bond angle. Hence cations are smaller than anions.

The bond angles of O3+, O3, and O3- can be ordered as O3- < O3 < O3+ from smallest to largest based on electron geometry and electron-electron repulsion.

When ordering the bond angles of O3+, O3, and O3- from smallest to largest, we must consider the electron geometry of each molecule/ion. In general, bond angles tend to decrease as the number of non-bonding electron pairs increases, due to the increased electron-electron repulsion.

In the case of O3+, it has fewer non-bonding electron pairs than neutral O3, leading to greater bond angles. O3, or ozone, has a bent molecular geometry, with a bond angle of roughly 117 degrees. O3-, or the ozone ion, has more non-bonding electrons, which will reduce the bond angle.

So, the bond angles would most likely be ordered as follows: O3- < O3 < O3+.

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D

Molecular motion increases as temperature increases and therefore increasing the molecular motion increases collision frequency.

Explanation:

When a substance is heated, its molecules gain increased kinetic energy even as the substance increases in temperatures. With higher kinetic energy, this means the molecules are moving more rapidly and hence collision between the molecules will be more frequent and of higher energy. It is these high energy collisions that cause the molecules to move further away from each other with increased temperatures (why substances expand).  

Learn More:

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Answer: Your answer would be D

Explanation: This is because whenever the collision increases the molecular motion increases with it.

Answer:

A.

Explanation:

A base is a substance that produces hydroxide ions in an aqueous solution.

A base is defined as a compound that produces hydroxide ions in solution (option A).

A base in chemistry is a water-soluble compound having bitter taste, that turn red litmus blue, and react with acids to form salts.

Asides the above properties of a base, a base is capable of producing hydroxide ions (OH-) when dissociated in an aqueous solution.

Examples of bases that would dissociate in water to produce hydroxide ions are as follows:

Therefore, option A is correct.

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Answer:

a. Be and Mg

Explanation:

Be (beryllium) and Mg (magnesium) are both found in the alkaline earth metals family (group 2) on the periodic table. Elements in the same family or group have similar properties,

Ca and Br are in groups 2 and 17

Cl and Ar are in groups 17 and 18

Na and P are in groups 1 and 15

Answer:

Based on whether an element is a metal or non-metal, or their charge if given.

Explanation:

Cations are positively charged ions. Elements that are metals become positively charged.

Anions are negatively charged ions. Elements that are non-metals become negatively charged.

To identify the cation and anion in an ionic compound, name the cation first and the anion second without including the word 'ion'. If the cation can have multiple charges, include either the oxidation number according to the Stock system or use -ous/-ic suffixes in the classical system. The formula must reflect a balance of total positive and negative charges to ensure electrical neutrality.

To identify the cation and anion in an ionic compound, you follow specific nomenclature rules. The name of the ionic compound is written with the cation name first, followed by the anion name, without using the word ion for either. For example, to name Ba(NO₃)₂, you would call it barium nitrate, naming the metal barium as the cation followed by the anion nitrate.

When a cation has more than one possible charge, the compound is named either using the Stock system, which includes the cation's oxidation number, or by using the classical system, which includes the Latin-based name of the cation with the suffix -ous or -ic. For instance, FeCl₃ is named iron(III) chloride in the Stock system or ferric chloride in the classical system because iron can have multiple oxidation states.

To determine the correct number of ions for the formula, the overall charge of the compound must be neutral. This means the total positive charge of the cations must balance the total negative charge of the anions. Thus, writing the chemical formula involves deducing the correct ratio of ions so that their charges cancel each other out.

Answer:

Minimizing repulsion by maximizing the bond angles

Explanation:

VSEPR is defined as 'valence shell electron pair repulsion' theory. The key principle is that repulsion of adjacent lone pairs of electrons or the electrons that are shared within a bond creates bond angles.

The bond angles are maximized in order to minimize the repulsion in the most stable geometrical shape of the molecule.

That said, in VSEPR theory we tend to achieve the greatest possible angles between the bonds and lone pair electrons in order to obtain the lowest repulsion between them.

Answer:

The fraction of original isotope remaining after 12 weeks is 1/8 (0.125)

Explanation:

The half life of the radio-isotope = 4 weeks =[tex]t_{\frac{1}{2}}[/tex]

After n half lives, the fraction of original isotope remaining = [tex]\frac{1}{2^{n}}[/tex]

In 12 weeks, the number of half lives = 12/4 = 3 half lives

The fraction of original isotope remaining = [tex]\frac{1}{2^{3}}=\frac{1}{8}[/tex]

Hence, after 12 weeks, fraction of original isotope remaining is 1/8 (0.125)

Answer:

Newton's second law of motion is F = ma, or force is equal to mass times acceleration. Learn how to use the formula to calculate acceleration

Explanation:

Answer:

Newton's laws can be experimentally verified because Newton's second law of motion is F = ma, or force is equal to mass times acceleration. Learn how to use the formula to calculate the acceleration. And so, using the equations and formulas we can use them and verify the laws.

Explanation:

good luck yalls ;P

Answer:

1. [tex]0.5 g/mL[/tex]

2. [tex]0.88 g/cm^3[/tex]

3. It has the greatest mass to volume ratio

4. Incomplete

5. [tex]H^+ (aq)+OH^-(aq)\rightleftharpoons H_2O (l)[/tex]

6. 1

7. Gloves, goggles, coat, mask

8. Flush with tap water for at least 15 minutes

9. The facts are listed below

10. Mass and volume

12. All matter consists of moving particles, the degree of their movement is directly proportional to their kinetic energy

Explanation:

1. In order to solve for density, we should know that density is the ratio between mass and volume of a liquid. In this case, we're given both measures: given mass of m = 20 g and volume of V = 40 mL, we may simply apply the equation of density described here:

[tex]d=\frac{m}{V}[/tex]

Substituting the variables, we obtain:

[tex]d=\frac{m}{V}=\frac{20 g}{40 mL}=0.5 g/mL[/tex]

2. Given a mixture of several liquids, it's important to understand that liquids with a greater density will tend to form a bottom layer of a solution, while liquids with a lower density will tend to form a top layer of a solution. Here we have a liquid with a density of [tex]d_1 = 1.0 g/cm^3[/tex] and another liquid with a density of [tex]d_2 = 0.88 g/cm^3[/tex]. Notice that [tex]d_1[/tex] > [tex]d_2[/tex].

This implies that the liquid with a density of [tex]0.88 g/cm^3[/tex] would be on top, as its density is lower than the density of the other liquid with a density of [tex]1.0 g/cm^3[/tex].

3. The solid phase is not always, but typically denser than liquids or gases. There are some exceptions to this rule, for example, ice, a solid phase of water, is less dense than liquid water.

However, for the majority of cases this statement is true. Remember that solid phases are the most ordered phases with atoms being packed closely to each other. In liquids, atoms are more dispersed with distances between them being greater than those in solids. Similarly, gases have the greatest distances between gas atoms among all three phases.

Since density is directly proportional to mass, let's say we take the same volume of a solid, a liquid and a gas. For the same volume, since we'll have a greater number of solid atoms than for a liquid or a gas (because solid atoms are more closely packed with lower average distances between the atoms), the mass to volume ratio will be the greatest for solids.

4. This seems to be an incomplete question.

5. In order to balance the following ionic equation, we need to follow the mass and charge balancing rules. Firstly, expand a water molecule showing the individual parts of it:

[tex]H-OH[/tex]

Secondly, notice that we need to add a hydroxide anion to the proton, so that we obtain the same number of protons and hydroxide anions on the left side, as well as the number of hydrogen and oxygen atoms on the right. This way, the net charge on the left hand side (0) and the net charge on the right hand side (0) are equal, so the charge is balanced as well. We obtain:

[tex]H^+ (aq)+OH^-(aq)\rightleftharpoons H_2O (l)[/tex]

6. We should be familiar with the ionization constant of water in the context of this problem. It is defined as the product between the hydronium ions and hydroxide ions and is a constant number at some given temperature. For pure water, the concentration of hydronium ions is balanced by the concentration of hydroxide anions to yield a neutral pH value, meaning the ratio of one with respect to the other would be 1.

For example, at room temperature, the ionization constant of water is defined as:

[tex]K_w=[H^+][OH^-]=10^{-14}[/tex]

Since we have pure water:

[tex][H^+]=[OH^-]=\sqrt{10^{-14}}=10^{-7}[/tex]

Then the ratio is:

[tex]\frac{[H^+]}{[OH^-]}=\frac{10^{-7}}{10^{-7}}=1

7 to 12. The questions are explained in the file attached.

Answer:

2Ag₂O  →  4Ag + O₂

Explanation:

Chemical equation:

Ag₂O  →  Ag + O₂

Balanced chemical equation:

2Ag₂O  →  4Ag + O₂

The given reaction is the decomposition of silver oxide. The silver oxide is decomposed into its constituent element silver and oxygen.

Decomposition reaction:

It is the reaction in which one reactant is break down into two or more product.

AB → A + B

This reaction also followed the law of conservation of mass because there are equal number of atoms of all elements on both side of equation.

Law of conservation of mass:

According to the law of conservation mass, mass can neither be created nor destroyed in a chemical equation.

This law was given by french chemist  Antoine Lavoisier in 1789. According to this law mass of reactant and mass of product must be equal, because masses are not created or destroyed in a chemical reaction.

Oxygen is the most active non-metallic element in Group 16 of the periodic table, also known as the oxygen family. This is primarily due to its small atomic size relative to other elements in the group.

The most active non-metallic element in Group 16 of the periodic table is oxygen. Group 16 elements are also known as the oxygen family. These elements become less active as you move down the group due to an increase in atomic size, which contributes to a decrease in electronegativity. Among the members of this group, oxygen has the smallest atomic size, making it the most active nonmetal in this group. Examples of other elements in this group are sulfur, selenium, tellurium, and polonium, but oxygen is significantly more reactive.

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Answer:

I think the answer is 13H

Explanation:

The best known example of a naturally-occurring radioisotope is uranium. All but 0.7 per cent of naturally-occurring uranium is uranium-238; the rest is the less stable, or more radioactive, uranium-235, which has three fewer neutrons in its nucleus.

Answer & Explanation:

D orbitals begin filling with electrons after the orbital found in the 4s sublevel is filled. This occurs because the d sublevel is first found in the.

Answer:

Interesting question.

Explanation:

D orbitals begin filling with electrons after the orbital found in the 4s sublevel is filled.

Have a good day

Answer:

Grass, deer, wolf, fungi.

Explanation:

The tropical level of an organism is defined as the position of organism occupied in the food chain. The food chain is starts from tropical level one which is primary producers (such as plants), then move to herbivores (such as deer) in level two, carnivores, (such as wolf) at level three, apex predators in level four (such as lions), and it ends in decomposers such as fungi.

Fungi play important role in ecosystem to help in breakdown of dead organic matter and return nutrients to the soil. Without fungi nutrients cannot cycle in an ecosystem, and causing the breakdown of entire food web.

Answer:

Halogens have 7 valence electrons.

Explanation:

They are the most active non-metals including fluorine, chlorine, bromine, iodine, and astatine

Answer:

464.1 J absorbed.

Explanation:

Given data:

Specific heat of zinc =  0.39 J/g°C

Mass of zinc = 34 g

Temperature changes = 22°C to 57°C

Energy absorbed or released = ?

Solution:

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance

ΔT = change in temperature

ΔT = 57°C -  22°C

ΔT = 35°C

Q = m.c. ΔT

Q = 34 g. 0.39 J/g°C. 35°C

Q = 464.1 J

Answer:

Positive effect -  allow the search and development of environmental friendly sources, to decrease the risk of polluents in the ozone (in the world).

Negative effect - environmental imbalances like: toxic gas leaks, river and soil contamination, etc.

Explanation:

   Ozone (O3) is one of the gases that make up the atmosphere and about 90% of its molecules are concentrated between 20 and 35 km altitude, called the Ozone Layer. Its importance is that it is the only gas that filters out type B ultraviolet radiation (UV-B), which is harmful to living beings.  

  Ozone has different functions in the atmosphere depending on its altitude. In the stratosphere, ozone is created when solar ultraviolet radiation interacts with the oxygen molecule, breaking it into two oxygen atoms (O). The released oxygen atom attaches itself to an oxygen molecule (O2), thus forming ozone (O3). In the stratospheric region, 90% of type B ultraviolet radiation is absorbed by ozone.  At ground level in the troposphere, ozone loses its protective function and becomes a polluting gas, responsible for increasing surface temperature, together with carbon monoxide (CO), carbon dioxide (CO2), methane (CH4) and nitrous oxide.

  Several chemicals are destroying ozone. By reacting with it, the nitric and nitrous oxides expelled from vehicles and the CO2 produced by burning fossil fuels such as coal and oil are destroying the protective layer of the planet, opening holes in it.

  To reduce gas emissions, chemical professionals have been studying in depth the substitution of fossil energy, which generates a lot of pollution, by the so-called renewable energy. Other example can be the electric car, which is environmentally friendly because it does not emit polluting gases, is already a reality, sold in many countries. So, this a positive effect of chemistry nowadays, which it can allow the search for environmental friendly sources, to decrease the risk of polluents.

     But associated with progress, we have a multitude of environmental imbalances. Toxic gas leaks, river and soil contamination and poisoning by ingestion of contaminated food are problems shown daily - these could be some negative effects of chemistry nowadays.

Answer:

The benefits of CFCs include their use as coolants.

CFCs can be used as foaming agents and fire extinguishers.

CFCs, when released into the atmosphere, destroy ozone in the stratosphere.

CFCs destroy ozone in the stratosphere, which is the chemical layer that shields living things from too much ultraviolet radiation from the sun.

Answer: Adolf Hitler was a German politician and he made the Nazi Party. He rose to power when he was the chancellor. He was also a dictator and he caused World War 2 when he invaded Poland September 1, 1939.

Answer: Adolf Hitler created the Nazi Party. He was a dictator and he rose to power when he was the chancellor in 1933 and then Fuhrer in 1934. He was the cause of World War 2 when he had invaded Poland.

*Fuhrer is a German term which means "The Leader".

Answer:

7628 y

Explanation:

Carbon-14 is radioactive and it follows the first-order kinetics for a radioactive decay. The first-order kinetics may be described by the following integrated rate law:

[tex]ln(\frac{[A]_t}{[A]_o})=-kt[/tex]

Here:

[tex][A]_t[/tex] is the mass, moles, molarity or percentage of the material left at some time of interest t;

[tex][A]_o[/tex] is the mass, moles, molarity or percentage of the material initially, we know that initially we expect to have 100 % of carbon-14 before it starts to decay;

[tex]k = \frac{ln(2)}{T_{\frac{1}{2}}}[/tex] is the rate constant;

[tex]t[/tex] is time.

The equation becomes:

[tex]ln(\frac{[A]_t}{[A]_o})=-\frac{ln(2)}{T_{\frac{1}{2}}}t[/tex]

Given:

[tex]\frac{[A]_t}{[A]_o} = \frac{40.0 %}{100.0 %}[/tex]

[tex]T_{\frac{1}{2}} = 5770 y[/tex]

Solve for time:

[tex]t = -\frac{ln(\frac{[A]_t}{[A]_o})\cdot T_{\frac{1}{2}}}{ln(2)}[/tex]

In this case:

[tex]t = -\frac{ln(\frac{40.0\%}{100.0\%})\cdot 5770 y}{ln(2)}[/tex]

[tex]t = 7628 y[/tex]

Answer:

A: 238 g

B: 224 g

Explanation:

Data given:

A.

number of moles of H₂O₂ = 7.00 mole

mass of H₂O₂ = ?

B.

number of moles of NaOH = 5.60 mole

mass of NaOH = ?

Solution:

Part A:

Formula will be used

               no. of moles = mass in grams / molar mass

As we have to calculate mass of substance

So, rearrange the above equation

             mass in grams =  no. of moles x molar mass . . . . . . (1)

Molar Mass of H₂O₂ = 2(1) + 2(16)

Molar Mass of H₂O₂ = 2 + 32

Molar Mass of H₂O₂ = 34 g/mol

Put values in equation 1

                 mass in grams = 7.00 mol x 34 g/mol

                 mass in grams =  238 g

mass of H₂O₂ = 238 g

_______________________

Part B:

Formula will be used

               no. of moles = mass in grams / molar mass

As we have to calculate mass of substance

So, rearrange the above equation

             mass in grams =  no. of moles x molar mass . . . . . . (1)

Molar Mass of NaOH = 23 + 16 + 1

Molar Mass of NaOH  = 40 g/mol

Put values in equation 1

                 mass in grams = 5.60 mol x 40 g/mol

                 mass in grams =  224 g

mass of NaOH = 224 g

8) 21.504 liters of gas

9) 122.5 g

10) 6.022*10^23

Explanation:

8)

1 mole= 22.4 liters

to calculate the volume of gas of 0.960 moles of CH4

22.4*0.960/1

= 21.504 liters of gas  

9)

2.0 mole*18.02 g/ 1 mole

=122.5 g

10)

2.0 l * 1 mole/22.4 l

6.022*10^23

this will have ur answer

       .

   .   pb  .

        .

Answer:

provide rewards to use solar power

Explanation:

Using solar power we can avoid bad energy like Coal, oil, natural gas, uranium and water from a dam.

All these kinds of energy producing air pollution, water pollution, or greenhouse gases.

But solar power has some toxic materials, also, using a lot of water to keep and clean solar power. In addition, if we create a solar power near a river or lake may cause damage.

We must think in these factors before to do a solar power.

Answer:

The scientist have developed to classify organisms because the living things with similarities can put into groups, which can further make easy to understand the relationship between them.

Explanation:

The scientist have classified organisms in different groups which can make their study easier. In this manner the organisms with same character will be in same group and their relationship and behavior with themselves as well as with others can be studied easily. It will make things less confusing. In this way the inheritance and genetic behavior can also be studied easily. This classification are based on various other categories like structure, function and also relationship with others.

Answer:

'classification allows for better identification of new organisms.'

Explanation:

Answer:

19.12 moles of NO will produced.

Explanation:

Given data:

Mass of ammonia = 325 g

Moles of NO produced = ?

Solution:

Chemical equation:

4NH₃ + 5O₂ → 4NO + 6H₂O

Number of moles of Ammonia:

Number of moles = mass/ molar mass

Number of moles = 325 g/ 17 g/mol

Number of moles = 19.12 mol

Now we will compare the moles of ammonia and NO.

                   NH₃              :                NO

                      4                :                 4

                     19.12           :              19.12

Thus 19.12 moles of NO will produced.

Answer:

7

Explanation:

Atomic number of X = 3

Atomic mass of X = 6.94 amu

1st isotope atomic mass = 6 amu

2nd isotope atomic mass = 7 amu

Which is more abundant isotope = ?

Explanation:

we know there are two naturally occurring isotopes of given element X, X-6  and X-7.

First of all we will set the fraction for both isotopes

x for the isotopes having mass 6

1-x for isotopes having mass 7

The average atomic mass of X = 6.94 amu

we will use the following equation,

6x + 7 (1-x) = 6.94

6x + 7 - 7x = 6.94

6x- 7x = 6.94 - 7

-1x = -0.06

x= -0.06/-1

x= 0.06

0.06 × 100 = 6%

6% is abundance of X-6 because we solve the fraction x.

now we will calculate the abundance of X-7.

(1-x)

1-0.06 =0.94

0.94 × 100= 94%

94% for X-7.

Answer:

3

Explanation:

Primary waves are radiated along a single direction, but secondary waves are radiated along all directions. That is why the P waves can take place in almost all mediums such as solid, liquid and air, unlike the S waves that are transverse and only travel through solid mediums