Which of these statements are true? Select all that apply. The Delta. Hf for Br2(I) is 0 kJ/mol. The Delta. Hf for He(I) is 0 kJ/mol. The Delta. Hf for Hg(I) is 0 kJ/mol. The Delta. Hf for Cl2(g) is 0 kJ/mol. The Delta. Hf for N2(I) is 0 kJ/mol.

Answer:

Q1= 9.42

Q2= 227 KJ

Q3= 31.4 KJ

Qt=269 KJ

Explanation:

First you have to find the heat needed to make ice at a temperature of -45 C to pass to a temperature of 0 C.

You're given the formula so all you have to do is replace by the data you're given (remember to make the Celsius, Kelvin by adding 273.15 to the Celsius since the magnitudes of temperature they're giving you in the constants are the Kelvin)

Q1= (2.093 J/gxK)(100 g)(45 K)

Q1=9418.5 J

Q1=9.4185 KJ≈9.42 Kj(you're asked to give your answer in KJ)

You know have to find the energy needed to liquify the ice, in other words you need to use the enthalpy of fusion to determine the energy that's being used, and since you have 100 grams of water, you only need to find the number of moles present in 100 grams of water by dividing the number of grams by the molar mass of water (18 g/mol) and then replace in the equation.

Q2=(5.56 mol)(40.7 KJ/mol)

Q2=227 KJ

You know have to find the energy needed to raise the temperature of water from 0 C to 75 C. You do the same thing as you did in the first step:

Q3=(4.184 J/gxK)(100 g/)(75K)

Q3=31380 J

Q3=31.38 KJ≈31.4 KJ

For the final step, you only add the Qs of each step:

9.42KJ+227KJ+31.4KJ= 267.82 KJ ≈ 267.8 KJ

Why do you use these procedures?

Well, you could simply have made a unique equation at first sight that involved the changes of temperature from -45 C to 75 C, but you have a phase change in the middle. Phase change keep temperature constant but they require heat from the surroundings in order to, in the case of ice, break the bonds that keep the molecules tight together.

This heat required from the surroundings is the Enthalpy of phase change, in this case enthalpy of fusion.

an atom because its the smallest thing in the entire world and in all orgnaisms

Answer:

1) Molar mass of NaOH can be calculated by taking the atomic mass values in the periodic table. Na (Sodium) = 22.98g/mol, O (Oxygen) = 16g/mol, H (Hydrogen) = 1.01g/mol

Add all the the mass values together for NaOH's molar mass, so (22.98 + 16 + 1.01) = 39.99 or round it to 40g/mol

2) To find the atoms from the moles, you just multiply Avogadro's number (6.02 x 10^23) by the moles.

So 3.35 x (6.02 x 10^23) = 2.0167 x 10^24 atoms are in 3.35 moles of aluminum

3) If the question is asking under standard temperature and pressure, we know that if we divide the volume by the molar volume of a gas (which is 22.7 in standard temperature and pressure), we can get the moles.  

So 101.25L / 22.7 = 4.46 mol

4) We know that to find the moles, it is the mass divided by the molar mass. If we rearrange the equation to solve for mass, we have to multiply the moles by the molar mass to get there.

Nitrogen's (N) molar mass on the periodic table is 14g/mol, but since Nitrogen is a diatomic element, it would be N2 by itself. So multiply 14 by 2, which will give you 28g/mol. N2's molar mass is 28g/mol.

Now you multiply 13.7 moles by 28g/mol, which will give you 383.6g

5) Now here I think you may have wrote the question wrong. Molecules would be at a way higher number than just 78.5, so I'm first just going to assume you meant 78.5g.

To get the moles from mass, you divide the mass of the compound by its molar mass. Molar mass of CaCO3 can be just calculated using the atomic mass values for each element in the compound (Ca is 40.07g/mol, C is 14g/mol, O3 would be 16 x 3 g/mol or just 48g/mol) and then adding them all together (40.07 + 14 + 48 = 102.07) which would give us 102.7g/mol.

Now, just divide the mass 78.5g by the molar mass 102.7g/mol

78.5/102.7 = 0.764 moles

Now on the offchance that you were actually referring to molecules, and you accidentally typed a different number doing this, you can find out the moles from the molecules by just dividing the number of molecules you have with avogadro's number (6.02 x 10^23)

So it would look something like this:

molecules of CaCO3 / 6.02 x 10^23

Answer:

Temporary hardness of water is caused when thermally unstable chemicals like magnesium hydrogen carbonate and calcium hydrogen carbonate are dissolved in water. Temporary hardness is treated by heating the hard water.

Hope that helps. x

Answer:

Solid, liquid, and gas are common states of matter. Because each particle is attached to several others, individual particles cannot move from one location to another, and the solid is rigid. A has a fixed volume but does not have a fixed shape. Liquids take on the shape of the container they are in.

Explanation:

sorry, this is what i think

Answer:

what is your question tell may i can help you

Answer:

decrease as we go down a group I know ionisation energy increases from left to right across the periodic table

Answer:

gasese molecules are always in free state

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Answer:

Solid  liquids , plasma gas

Explanation:

It retains its shape regardless of the shape of the container

Answer:

Halogen Family of elements

Explanation:

Group Seventeen

The density of the gas is obtained as  0.55 g/L.

We can find the density of the gas using the relation;

PM = dRT

P = pressure of the gas

M = molar mass of the gas

d = density of the gas

R = gas constant

T = temperature

Now;

P = 29.9 kPa

R = 8.314 L·kPa mol·K.

T =  147°C + 273 = 420 K

d = ?

M = 64 g/mol

Substituting values;

d = PM/RT

d =  29.9 kPa ×  64 g/mol/ 8.314 L·kPa mol-1K-1 420 K

d = 1913.6/3491.88

d = 0.55 g/L

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6.5 moles of AgCl can be formed from 6.5 moles of Ag.

STOICHIOMETRY:

According to this question, silver reacts with hydrochloric acid to form silver chloride and hydrogen gas as follows:

2Ag + 2HCl → 2AgCl + H2

Based on this balanced equation, 2 moles of silver (Ag) produces 2 moles of silver chloride (AgCl).

This means that 6.5 moles of Ag will produce (6.5 × 2)/2 = 6.5 moles of AgCl.

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Answer:

The answer is D. Kinetic energy is the energy of motion.

Pls mark brainliest. Hope this helped. :D

Answer:

B. 1s,2s,2p,3s

Explanation:

Answer:

B cells and T cells. The B cells produce antibodies that are used to attack invading bacteria, viruses, and toxins. The T cells destroy the body's own cells that have themselves been taken over by viruses or become cancerous.

Explanation:

The question that will best help the student to classify the material is; "is the material malleable or ductile?"

Generally, materials can be classified as metals or non metals. There are properties that are particular to metals and there are properties that are particular to nonmetals and these properties can be used to identify each one of the materials.

The question that will best help the student to classify the material is; "is the material malleable or ductile?" These metallic properties.

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Missing parts;

A student is trying to classify an unidentified, solid gray material as a metal or a nonmetal. Which question will best help the student classify the material? A. Is the material malleable or ductile? B. Does the material feel hard to the touch? C. Will the material float in water? D. Does the material feel rough or smooth?

Explanation:

most common elements that bond with oxygen is Hydrogen (H2) to form water

Answer:

It is strongly recommended that students do NOT wear contacts lenses in the laboratory. Chemical vapors may penetrate the contact lens material and cause the lens to adhere to one's eye, which could be detrimental to the eye. Goggles are not vapor tight and do not completely eliminate this absorption.

Answer:

D

Explanation:

Protons and Neutrons both have a mass of about 1 amu so you add them but electrons have a mass of 0 amu so they are left out.

Answer:

d] 74.1 cm²

Explanation:

Product means that the values given must be multiplied.

13 cm × 5.7 cm = 74.1 cm²

Answer:

He put segregationists in charge of federal agencies...

Explanation:

...

Answer:

He placed segregationists in charge of federal agencies.

Explanation:

Assuming the surface on which the box moves is frictionless, the rate at which the box accelerate is equal to 0.5 [tex]m/s^2[/tex].

Given the following data:

To determine the rate at which the box accelerate, assuming the surface on which the box moves is frictionless:

Mathematically, Newton's Second Law of Motion is given by the formula;

[tex]Force = mass \times acceleration[/tex]

Making acceleration the subject of formula, we have:

[tex]Acceleration =\frac{Force}{mass}[/tex]

Substituting the given parameters into the formula, we have;

[tex]Acceleration = \frac{25}{50}[/tex]

Acceleration = 0.5 [tex]m/s^2[/tex]

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Answer:

Oxygen, heat, and fuel

Explanation:

Oxygen, heat, and fuel are frequently referred to as the "fire triangle." Add in the fourth element, the chemical reaction, and you actually have a fire "tetrahedron." The important thing to remember is: take any of these four things away, and you will not have a fire or the fire will be extinguished.

Answer:

From bottom to top, Troposphere, Stratosphere, Mesosphere, Thermosphere, & at the top, Exosphere.

Explanation:

Answer:

The mixture of cryolite and aluminum oxide has a lower melting point than pure aluminum oxide. This means a lower amount of energy is required to establish effective conditions for electrolysis and thus makes it more cost effective.

Explanation:

Answer:

1 grams Cobalt(II) Sulfate = 0.006451787725861 mole using the molecular weight calculator and the molar mass of CoSO4.

Explanation:

Answer:

This is a reflector telescope and  in which it captures different wavelengths of light and it hits one mirror, bounces back and hits another and then is shown through the eyepiece. It captures all of the visible spectrum and some areas above and below it. These telescopes are better for seeing big picture and not the fine details in planets surfaces.

Hope this helps!

Explanation:

Answer:

This is a reflector telescope and  in which it captures different wavelengths of light and it hits one mirror, bounces back and hits another and then is shown through the eyepiece. It captures all of the visible spectrum and some areas above and below it. These telescopes are better for seeing big picture and not the fine details in planets surfaces.

Hope this helps!

Explanation:

Considering the rule of three and molar mass of O, the mass of O²⁻ ions in 3 mol of alumina Al₂O₃ is 96 grams.

By multiplying the number of moles by the subscripts next to each atom, you get the amount of each element present in the compound. IIf the same atom appears more than once in the compound, you must add its amounts.

So, in 1 mole of Al₂O₃, you have 2 ions of O²⁻.

Then you can apply the following rule of three: if 1 mole of the compound contains 2 ions of O²⁻, 3 moles of the compound contains how many ions of O²⁻?

[tex]amount of ions of O^{2-} =\frac{3 moles of Al_{2} O_{3} x2 ions of O^{2-}}{1mole of Al_{2} O_{3} }[/tex]

amount of ions of O²⁻= 6 ions

Being the molar mass of O 16 g/mole, this is the amount of mass that a substance contains in one mole, then the mass of O²⁻ can be calculated as:

6 x 16 g/mole= 96 grams

Finally, the mass of O²⁻ ions in 3 mol of alumina Al₂O₃ is 96 grams.

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