Selenium-81 has an abundance of 21.91% and a mass of 80.65 amu.
Selenium-84 has an abundance of 23.35% and a mass of 83.67 amu.
Selenium-80 has an abundance of 54.74% and a mass of 79.64 amu.
What is the average atomic mass of Selenium according to these values?

Answer:

Where can you find most of Earth's liquid freshwater?

Explanation:

Over 68 percent of the fresh water on Earth is found in icecaps and glaciers, and just over 30 percent is found in ground water. Only about 0.3 percent of our fresh water is found in the surface water of lakes, rivers, and swamps.

Hope that helped, i also have snap if you need me.

Over 68 per cent of the fresh water on Earth is found in icecaps and glaciers, and just over 30 per cent is found in groundwater. Only about 0.3 per cent of our freshwater is found in the surface water of lakes, and rivers.

The Earth is a watery place. About 71 per cent of the Earth's surface is water-covered, and the oceans hold about 96.5 per cent of all Earth's water.

The majority of Earth’s fresh water is stored in underground aquifers.

Aquifers are layers of sedimentary formations such as sandstone and fractured hard rocks where water after infiltration from soil reaches and fill the interstitial spaces.

Aquifers are huge in size in basins and contain a huge amount of underground water of fresh quality.

So, over 68 per cent of the freshwater is present on Earth.

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#SPJ2

Answer:

it's A. if the force of gravity is greater than the buoyant force, the object will sink.

Explanation:

just took the quiz on a p e x

Answer:

the answer is HYPOTHESIS your welcome

Explanation:

Answer:

2. Worm Y reproduces sexually, which gives it genetic variation.

Answer:

B      Worm Y reproduces sexually, which gives it genetic variation.

Explanation:

hope you all have a good day

Answer:

im pretty sure the answer is b

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PLEASE MARK ME BRAINLIEST ☺️

Answer:

the answer is {organisms}

Answer:

organisms

Explanation: I took the test

Answer:

Explanation:

To find the concentration of new solution we use the formula

[tex]C_1V_1 = C_2V_2[/tex]

where

C1 is the concentration of the stock solution

V1 is the volume is the volume of the stock solution

C_2 is the concentration of the diluted solution

V2 is the volume of the diluted solution

Since we are finding the the concentration of new solution

[tex]C_2 = \frac{C_1V_1}{V_2} \\[/tex]

From the question

C1 = 0.575 M

V1 = 298 mL

V2 = 750 mL

We have

[tex]C_2 = \frac{0.575 \times 298}{750} \\ = 0.228466666...[/tex]

We have the final answer as

Hope this helps you

The answer would be B.

yes they can be changed becasue they are expose to the environment

That's why it's improtant to have a calorimeter so the energy and heat are contained

The total energy of an open system be changed if:

According to the First Law of Thermodynamics, energy cannot be created or destroyed, it can only change form.

An open system is a system that has an interaction with its environment where matter or energy can be added or removed from the environment.

As a result of this, the total energy of an open system can be changed if there is an exchange between matter and energy and they remain constant.

Therefore, the correct answer is an exchange has to take place for the total energy in an open system to be changed.

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Answer:

It's probably C

The forces between liquid particles are weaker than the forces between solid particles. This means that liquid particles are further apart and can move about more easily. Since the particles can move, the liquid can flow and take the shape of its container

Sorry if the answer is wrong!!!!!!

Answer:

Explanation:

The density of a substance can be found by using the formula

[tex]density = \frac{mass}{volume} \\[/tex]

From the question

mass = 8.11 g

volume = final volume of water - initial volume of water

volume = 44.72 - 25.26 = 19.46 mL

We have

[tex]density = \frac{8.11}{19.46} \\ = 0.416752312...[/tex]

We have the final answer as

Hope this helps you

Answer:

Its B

Explanation:

Because im just built different

The statement  featuring the single replacement reaction has been statement B.

The single replacement reaction has been defined as the reaction of the highly reactive element with the compounds, that results in the formation of the new compound with the replacement of the less reactive element.

The single replacement reaction can be given as:

G + XY [tex]\rightarrow[/tex] GY + X

In the reaction, G being more reactive than X has been able to displace X and forms bond with Y. Thus, statement  featuring the single replacement reaction has been B.

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Answer:

Copper Atoms

Explanation:

All copper atoms have atomic number 29: all their nuclei contain 29 protons. But they also contain uncharged particles called neutrons. In natural copper, the atoms are of two kinds. One has 29 protons and 34 neutrons in the nucleus; the other has 29 protons and 36 neutrons

Answer:

2.08g

Explanation:

Given parameters:

  Volume of CuSO₄  = 3.29mL

  Molarity  = 4M

Unknown:

Mass of CuSO₄ = ?

Solution:

Let us find the number of moles from the given parameters first;

     Number of moles  = molarity x volume

           1000mL = 1L

Express the volume of the given CuSO₄ in L = 3.29 x 10⁻³L

   Number of moles  = 4 x 3.29 x 10⁻³ = 0.013mol

So;

  Mass of CuSO₄ = number of moles x molar mass

      Molar mass of  CuSO₄  = 63.6 + 32 + 4(16) = 159.6g/mol

 Mass of CuSO₄  = 0.013mol  x 159.6g/mol

 Mass of CuSO₄  = 2.08g

Answer:

Explanation:

You will need to look up the Standard Heats of Formation* for each substance and apply Hess's Law Equation.

ΔH⁰(rxn) = ∑ΔH⁰(Products) - ∑ΔH⁰(Reactants)

*Std Heats of Formation can be found in the appendix of most college chem texts.

For this problem:

Given               CaCO₃(s)       =>           CaO(s)        +      CO₂(g)

∑ΔH⁰:          -635.1 Kj/mole            -393.5Kj/mole         -1206.9

ΔH⁰(rxn) = [(-393.5 Kj/mole) + (-393.5Kj/mole)] - (-1206.9Kj/mole)

= (-635.1 -393.5 + 1206.9) Kj/mole

= +178.3 Kj/mole

Answer:

656.3 kJ

This reaction is endothermic

Explanation:

edge 2020

Answer:

0.219 g/mL.

Explanation:

From the question given above, the following data were obtained:

Mass = 25 g

Volume = 114 mL

Density =.....?

Density of a substance is simply defined as the mass of the substance per unit volume of the substance. Mathematically, it is expressed as:

Density = mass /volume

With the above formula, we can obtain the density of the substance given in the question above as follow:

Mass = 25 g

Volume = 114 mL

Density =.....?

Density = mass /volume

Density = 25/114

Density = 0.219 g/mL

Therefore, the density of the substance is 0.219 g/mL

Answer:

Irrational

Explanation:

:)

Answer:

It is irrational

Explanation:

Since 7 is a prime number, it has no square factors and its square root cannot be simplified.

Answer:

A

Explanation:

the number of molecule won't be twice as fructose has 12 hydrogen molecules and lactose has 22 hydrogen molecules

From the given statements, the statement saying that the number of atoms in Lactose is twice the number of atoms in Fructose is not correct. Thus option A is correct.

The given molecules in the list are Glutamine, Lactose, fructose, and Sorbitol.

The number of atoms in the following compounds is:

Statement A says that the number of atoms in Lactose is twice the number of atoms in Fructose. The twice atoms of Fructose are 48 atoms. The number of atoms of lactose is 45.

Thus statement A is incorrect. Thus option A is correct.

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I'm pretty sure its momentum

Answer:

For number 5 it is the 2nd one some stants has a mass of 1.25 g And the 2nd 1 number 6It is the 1st 1A subject has a melting point of 40

Answer:

i cry when im alone

Explanation:

Answer:

b-ovaries

Explanation:

Answer:

ovaries

Explanation:

i just know trust me tell me if its wrong

Answer:

During the process of reaching thermal equilibrium heat is transferred between the object. heat is always transferred from the object at the higher temperature to the object with lower temperature. For a gas, the heat transfer is related to a change in temperature.

Answer:

A) oxygen moles/sec = 48 * 10 ^-14  mol/sec

B) mass of oxygen = 1536*10^-14 grams

Explanation:

cross sectional area of cylinder = 2cm^2 = 2 * 10^-4 m^2

length of cylinder = 5 cm = 0.05 m

concentration at one end = 0.2 mol m^-3

concentration falls linearly at other end = 0.05 mol m^-3

Diffusion constant of oxygen = 8 * 10^-10  m^2 s^-1

A ) Number of moles of oxygen passing every second

 N = A * D * [tex]\frac{dc}{dt}[/tex]   ------- ( 1 )

A = area , D = diffusion constant,  [tex]\frac{dc}{dt}[/tex] = rate of change of diffusion

dc /dt = ( 0.2 - 0.05 ) / 0.05  = 3 mol m^-4

back to the equation

N = ( 2 * 10^-4 ) * ( 8 * 10^-10 ) * ( 3 ) = 48 * 10 ^-14  mol/sec

B) Mass of oxygen passing down the cylinder each second

This can be obtained by converting : 48 * 10^-14 moles to grams

1 mole of oxygen  =  32 grams of oxygen

therefore : 48 * 10^-14 moles of oxygen = ( 32 * (48*10^-14) = 1536*10^-14 grams

Answer:

1.55×10²² molecules.

Explanation:

We'll begin by calculating the number of mole in 5.32 g of pure lead (Pb). This can be obtained as follow:

Mass of Pb = 5.32 g

Molar mass of Pb = 207 g/mol

Mole of Pb =?

Mole = mass /molar mass

Mole of Pb = 5.32/207

Mole of Pb = 0.0257 mole

Finally, we shall determine the number of molecules in 0.0257 mole of Pb. This can be obtained as follow:

From Avogadro's hypothesis,

I mole of Pb contains 6.02×10²³ molecules.

Therefore, 0.0257 mole will contain = 0.0257 × 6.02×10²³ = 1.55×10²² molecules.

Therefore, 5.32 g of pure lead (Pb) contains 1.55×10²² molecules.