What is a quasar?
Two stars moving around each other.
A star that emits a repeated radio signal.
A star that emits intense radio and light energy.
A system of stars held together by gravity.
A collapsed star emitting no light.

A sample will likely affect a criminal case because this evidence will provide a nearly exact match to the suspect’s hair (Option D).

DNA testing refers to the techniques used to obtain DNA from samples that can be used to identify an individual in a police case. A sample of hair may be used for DNA testing because it contains cells and therefore also contains DNA.

Therefore, with this data, we can see that DNA testing allow us to identify individuals for which we need to obtain a sample with cells.

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The first thing will be to finish the reaction that happens in the experiment to the reactional HCl and sodium bicarbonate (NaHCO3). The balanced reaction is the following:

Now, we must determine which is the limiting reactant. To do this we are going to convert all the data they give us to moles.

For HCl we are given the molarity, so the moles will be:

Now the moles of sodium bicarbonate are found using its molar mass:

By stoichiometry, we have that one mole of NaHCO3 reacts with one mole of HCl. We have more moles of NaHCO3 than HCl. Therefore, HCl will be the limiting reactant.

So the reaction will occur according to the number of moles of HCl. Now the ratio between HCl and CO2 gas formed is 1 to 1. For one mole of HCl that reacts, 1 mole of CO2 will be formed.

so, the number

Answer: C4H10O2

Explanation:

At first find the percentage composition, in 1.67 g compound what percentage of Carbon, Hydrogen and Oxygen are there. Then from those percentages through unitary method find out how much Carbon, Hydrogen and Oxygen would be there in 90.1 g of compound. From those amounts finds their mole number, as in divide the obtained amount by their gram equivalent mass. The numbers you obtain are the corresponding number of Carbon Hydrogen and Oxygen in one molecule of the compound. Hope this helps

Answer:

Explanation:

Here, we want to give the names or formulas of the given hydrates

1) Magnesium sulfate heptahydrate

The first thing we have to do here is write the formula for magnesium sulfate.

Hepta means 7, which is pointing to the fact that there are 7 water molecules

We can have this as:

6) Here, we can see that the element involved is cobalt with an oxideation number of 2. We also have just one water of crystallization

So, we have the name of the compound as:

Order these elements Ca, Be, Ba, and Sr:

If we take a look at the periodic table trends we will see that the atomic radii increases from left to right and from top to bottom.

So let's look for our elements:

Be: atomic number 4

Ba: atomic number 56

Ca: atomic number 20

Sr: atomic number 38

They are all Alkaline Earth Metals, they are in the same group.

So we said that the atomic radii increases from top to bottom. If we have to arrange them in order of decreasing atomic radii, we have to put first the largest one. The Barium is the one that is in a lower position, then Sr, then Ca and finally Be.

So the order of our problem is Ba, Sr, Ca and Be.

Which is the explanation?

As we move down in the periodic table the number of electrons increases. They all have 2 electrons in the outer shell. But let's look at the electronic configuration of two of them:

Ca:

Ba:

The correct formula of copper (II) sulfate is CuSO₄ because Copper ion (Cu²⁺) has +2 charge and sulfate ion SO₄²⁻ has -2 charge, while CuSO₃ is copper(II) sulfite.

The CuSO₄ molecule contains an ionic bond between the copper cation (Cu²⁺) and the sulfate anion (SO₄²⁻).

The copper sulfate in its pentahydrate form is given by the chemical formula CuSO₄.5H₂O. This form of copper sulfate is characterized by its bright blue color but the anhydrous form of this salt is a white powder.

The oxidation state of the copper atom in a CuSO₄ molecule is +2. The molar mass of the pentahydrate and anhydrous forms of copper sulfate are 249.685 grams/mole and  159.609 grams/mole respectively.

Anhydrous CuSO₄ has a powdery appearance and a grey-white, while the pentahydrate has a bright blue color.

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In order to properly balance an equation, we need to make sure that the same amount of elements on the reactants side matches the number of elements on the products side, we can do that by increasing the number in front of each molecule, the so called stoichiometric coefficient. In the reaction from the question we can properly balance by adding the following stoichiometric coefficients

For this question we have:

CaCl2 -> Ca + 2 Cl

Answer:

the more hotter the star, the more brightly it burns

Explanation:

someone just deleted my answer ugh sorry....ill write it again

so, te main sequence is a sequence in mass (and not a sequence in time).

The most massive stars are located at the the top left (since they are the brightest and hottest/bluest). The lowest mass stars are are located at the bottom left ( since they dimmer and cooler/redder).

Following the main sequence from the top left to the bottom right is thus a sequence from high to low mass.

Answer:

60.0 mL of 0.322 M potassium iodide are combined with 20.0 mL of 0.530 M lead (II) nitrate.

How many grams of lead (II) iodide will precipitate? (you must write your own reaction)

Explanation:

Co-60 is used medically for radiation therapy as implants and as an external source of radiation exposure the half-life of Co-60 is 5, 272 years 2.000 mg sample will remain after 21, 088 years is 0.0625 gm left

Radiation therapy is the cancer treatment that uses high doses of radiation to kill cancer cell and shrink tumor

Here given data is Co-60 is 5, 272 years and we have to find the number of half lives in 21, 088 years = ?

21, 088/5, 272 = 4 half lives

(1/2)⁵   = 1/32 nd  of the original will be left

1/32×2.000mg = 0.0625 gm left

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The final pressure of the sample gas based on the new volume and temperature would be 0.245 atm.

The combined gas law is expressed as:

[tex]\frac{p_1v_1}{t_1}[/tex] = [tex]\frac{p_2v_2}{t_2}[/tex]

Where

In this case, we were given all the variables except the final pressure, [tex]p_2[/tex]:

Making p2 the subject of the formula in the combined gas equation, we have:

[tex]p_2[/tex]= [tex]p_1v_1t_2/t_1v_2[/tex]

Next, let's substitute the given variables:

[tex]p_2[/tex]= 1.2 x 6.02 x 20.2/59.5 x 10.0

     = 145.9248/595

     = 0.245 atm

In other words, the final pressure when the sample of gas is administered to a new volume of 10.0 L at 20.2℃ is 0.245 atm'

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Answer:

Explanation:

Here, we want to get the maximum volume of solution that can be produced

Given:

Molarity = 1.8 M

Number of Moles = 0.9 moles

Find:

Volume

Equation Used:

Number of moles = molarity * volume

Answer:

To convert this to mL, we multiply the volume by 1000 since 1 L = 1000 mL

Thus, we have it that:

Answer:

Explanation:

Here, we want to calculate the mass of sodium chloride formed

Firstly, we need to get the number of moles of sodium that reacted

To get this, we divide the mass of sodium by its atomic mass

We have that as:

Now, let us get the number of moles of chlorine

From the equation of reaction, 1 mole of sodium produced 1 mole of sodium chloride

Thus, 0.5435 mole of sodium will also produce 0.5435 mole of sodium chloride

To get the mass of sodium chloride formed, we multiply the above number of moles by the molar mass of sodium chloride

The molar mass of sodium chloride is 58.44 g/mol

Thus, the mass of sodium chloride formed will be:

Step 1

The reaction must be written, completed, and balanced:

2 NaOH + H2SO4 => Na2SO4 + H2O

-----------

Step 2

Information provided:

Mass of NaOH = 40.0 g

Mass of H2SO4 = 60.0 g

--

Information needed:

The molar masses:

NaOH) 40.0 g/mol approx.

H2SO4) 98.0 g/mol approx.

-----------

Step 3

The limiting reactant?

By stoichiometry:

1 mole NaOH = 40.0 g

1 mole H2SO4 = 98.0 g

2 NaOH + H2SO4 => Na2SO4 + H2O

2 x 40.0 g NaOH ----------- 98.0 g H2SO4

40.0 g NaOH ----------- X

X = 40.0 g NaOH x 98.0 g H2SO4/2 x 40.0 g NaOH = 49.0 g H2SO4

For 40.0 g of NaOH, 49.0 g of H2SO4 is needed but is provided 60.0 g of H2SO4. Therefore, the excess is the H2SO4, and the limiting reactant is the NaOH.

Answer: the limiting reactant is NaOH

If the photon has a frequency of   3.16 × 10 ⁷ Hz, then the energy of the the photon as per Planck's law would be 1.978× 10⁻²⁶ Joules

It can be understood in terms of the distance between any two similar successive points across any wave.

C = λν

As given in the problem we have to calculate the energy of the light if the frequency of light is  3.16 × 10 ⁷ Hz

The energy of the photon = h ν

                                           = 6.26 × 10⁻³⁴ × 3.16 × 10 ⁷

                                           = 1.978× 10⁻²⁶ Joules

Thus, If the photon has a frequency of   3.16 × 10 ⁷ Hz, then the energy of the the photon as per Planck's law would be 1.978× 10⁻²⁶ Joules.

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The set of quantum numbers (3, 3, -3, -1/2), and  (2, 1, 2, +1/2) are not possible. Therefore, options c and e are correct.

The set of numbers that can describe the position and energy of the electron. We have four quantum numbers principal, azimuthal, magnetic, and spin quantum numbers.

Principal quantum numbers (n) tell about the principal electron shell of the atom and the most probable distance between the electrons and the nucleus. The azimuthal quantum number (l) tells about the shape of an orbital in which an electron is present. It has values equal to l = n - 1.

The magnetic quantum number tells about the total number of orbitals in a subshell and the orientation of these orbitals.  The value of m lies in between -l to +l. The value of the spin quantum number describes the direction of spin of an electron and it has only two values +½ and -½.

In option c, the principle (n) and azimuthal (l) quantum number has the same value but when n = 3 the possible values of l are 2, 1, 0. In option d, the magnetic quantum number has the value of 2 while l has 1 which is not possible because when l= 1 the values of m can be  +1, 0, and -1.

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The chemical formula of calcium (II) oxide is CaO, wherein the valency of both oxygen and calcium is two.

Chemical  formula is a way of representing the number of atoms present in a compound or molecule.It is written with the help of symbols  of elements. It also makes use of brackets and subscripts.

Subscripts are used to denote number of atoms of each element and brackets indicate presence of group of atoms. Chemical formula does not contain words. Chemical formula in the simplest form  is called empirical formula.

It is not the same as structural formula and does not have any information regarding structure.It does not provide any information regarding structure of molecule as obtained in structural formula.

There are four types of chemical formula:

1)empirical formula

2) structural formula

3)condensed formula

4)molecular formula

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This elements or substances that are not a metal are called non-metals.

I think that the answer is Non-metal

Explanation:

If n = 2 we have this posibility:

This shell contains 2 subshells: s and p

Subshell 2s can only contain 2 electrons

Subshell 2p can only contain 6 electrons

Answer: In total, we can have 8 electrons in n = 2

We start by counting the number of atoms of each element on each side of the reaction.

Now we balance the reaction by trial and error, starting with chlorine. We have 2 chlorine atoms in the reactants and 3 clear atoms in the products, so to balance we cross the coefficients placing 3 on the reactant side and two on the product side in the respective molecules:

Now we continue with the oxygens, we have 3 oxygens on the reactant side and 1 on the products, so we put the coefficient 3 on the products side in front of the respective molecule:

We now have the balanced equation. We have 3 Mg atoms, 6 Cl atoms, 2 Cr atoms, and 3 O atoms on each side of the reaction.

Answer:

Explanation:

Here, we want to calculate the density of the gas at STP

We use a modification of the general gas law as follows

Mathematically:

where:

P1 is the initial pressure which is 0.95 atm

D1 is the initial density which is 0.066 g/l

T1 is the initial temperature in Kelvin (we add the temperature in Celsius with 273 K : 32 + 273 = 305 K)

P2 is the pressure at STP which is 1 atm

D2 is the density that we want to calculate

T2 is the temperature at STP which is 273 K

Substituting the values, we have it that:

1) A precipitate called [tex]Fe(OH)_{2}[/tex]

2) A precipitate is formed called [tex]Mg(CH_{3} COO)_{2}[/tex]

The term precipitate is used to describe the product that is formed when there is a reaction between two aqueous phase reactants that leads to the formation of a solid product from the reaction as we can see from the image that is attached.

we now have to look at the reactions as we can see them in the mage that is attached. We must note that we can only say that a precipitate has been formed if the product is solid after we have mixed the aqueous phase reactants.

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Answer: 43.38 number of atoms

Explanation: If you look at this formula, then this one molecule contains six oxygen atoms. That means number of moles of oxygen atoms. That is six times the number of moles and of calcium nitrate, That is six, multiply 7.23, which comes out to be 43.38 moles of oxygen atom.

Answer

The specific heat of the glass = 0.7366 J/g°C

Explanation

Given:

Mass of the glass sample, m = 9.3 g

Quantity of heat given off, Q = 87 J

Change in temperature, ΔT = 12.7 °C

What to find:

The specific heat, c of the glass.

Step-by-step solution:

The specific heat, c of the glass can be calculated using the given formula below.

Putting the values of the given parameters into the formula, we have;

Therefore, the specific heat of the glass is 0.7366 J/g°C

To read the measuring cylinder we first count the number of smaller divisions between the marked interval. In this case it is 10 intervals. The marked intervals are 60 and 80, therefore between these values we have 20. We will now divide the 20 by the 10 intervalswhich is equal to 2. Now each interval has a numerical value of 2. We read from the bottom of the meniscus. The meniscus is ttouching the 5th line and so we say 5 x 2=10, we add this to 60.

Answer: 60+10= 70,

Answer:

A is the correct answer.

Explanation:

It is possible to reach 1°C and 1°F because they are both units of temperature. But 1k is not a unit of temperature.

87.77 ml will provide the recommended daily allowance of vitamin C.

- To calculate the milliliters of vegetable juice that will provide 100% of the recommended daily allowance of vitamin C, we can use a mathematical Rule of Three:

So, 87.77 ml will provide the recommended daily allowance of vitamin C.

Let's write the balanced chemical equation:

You can see that in the reactants and in the products we have the same number of atoms for each element. This is due to the matter of conservation law.

The total number of calcium atoms that are reacting and produced in the reaction is 3.

The frequency of the green light from a traffic signal is 5.76 * 10¹⁴ Hz

The frequency of the light is 1.85 * 10¹⁶ Hz

The frequency of the light is 4.84 * 10¹⁴ Hz

The energy of the photons is 1.172 * 10⁻³ J

The energy of the photons is 4.34 * 10⁻² J

The frequency of light can be found given the wavelength from the formula below:

8. The frequency of the green light from a traffic signal is calculated below:

velocity of light = 3.0 * 10⁸ m/s

wavelength = 5.2 x 10⁻⁷ m

Frequency = 3.0 * 10⁸ / 5.2 x 10⁻⁷

frequency = 5.76 * 10¹⁴ Hz

9. The frequency of the light is calculated below:

velocity of light = 3.0 * 10⁸ m/s

wavelength = 16.23 x 10⁻⁹ m

Frequency = 3.0 * 10⁸ / 16.23 x 10⁻⁹

frequency = 1.85 * 10¹⁶ Hz

10. The frequency of the light is calculated below:

velocity of light = 3.0 * 10⁸ m/s

wavelength = 6.2 x 10⁻⁷ m

Frequency = 3.0 * 10⁸ / 6.2 x 10⁻⁷

frequency = 4.84 * 10¹⁴ Hz

11. The energy of one of the photons will be calculated as follows:

E = hf

E = hc/λ

Energy of the photons =  2.3 x 10¹¹ x hc/λ

h = 6.626 * 10⁻³⁴Js

λ = 3.9 x 10⁻¹² m

c = 3.0 * 10⁸ m/s

E =   2.3 x 10¹¹ x 6.626 * 10⁻³⁴ * 3.0 * 10⁸ / 3.9 x 10⁻¹²

E = 1.172 * 10⁻³ J

12. The energy of one of the photons will be calculated as follows:

E = hf

E = hc/λ

Energy of the photons =  9.4 x 10¹⁶ x hc/λ

h = 6.626 * 10⁻³⁴Js

λ = 4.3 x 10⁻⁷ m

c = 3.0 * 10⁸ m/s

E =   9.4 x 10¹⁶ x 6.626 * 10⁻³⁴ * 3.0 * 10⁸ / 4.3 x 10⁻⁷

E = 4.34 * 10⁻² J

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Step 1

The reaction provided:

2 Mg (s) + O2 (g) => 2 MgO (s) (completed and balanced)

-----------

Step 2

Information provided:

40.0 g of O2 which react completely

---

Information needed:

The molar masses of:

O2) 32.0 g/mol

MgO) 40.3 g/mol

-----------

Step 3

By stoichiometry,

2 Mg (s) + O2 (g) => 2 MgO (s)

32.0 g O2 ------- 2 x 40.3 g MgO

40.0 g O2 ------- X

X = 40.0 g O2 x 2 x 40.3 g MgO/32.0 g O2

X = 101 g MgO

Answer: C 101 g