please help with this answe i do not how to to do it it

Answer:

5.452  cal/g

Explanation:

45.8 cal / 8.4 g =   5.4523  cal/g

384.72 J is the heat of fusion of the substance.

It is the change in the value of the enthalpy by providing energy i.e. heat, for a specific quantity of the substance.

Given data:

Heat of fusion  =?

Mass of substance = 8.4 g

Unknown:

Amount of energy required to melt the given mass = 45.8 cal

Solution:

To solve this problem, the amount of energy required to melt the substance is given as;

H  = m L

m is the mass

L is the heat of fusion

Insert the given parameters and solve;

H  = 8.4 g  x 45.8 cal = 384.72 J

Hence, 384.72 J is the heat of fusion of the substance.

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Thomson discovered the electron, the first subatomic particle. In 1904, Thomson proposed atomic model where electrons are embedded within spherically distributed, positive charge (so-called "plum pudding" model).

J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged "soup."

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Answer:

1.05 mols of O2 gas

Explanation:

For this type of problem, it's important to understand what the balanced Chemical equation tells us:

Let's look at the balanced chemical equation:

[tex]2Mg(s)+O_2(g)-- > 2MgO(s)[/tex]

This equation two sides of the reaction arrow.  On the left are the reactants (things you start with, and that react during the chemical reaction), and on the right side are products (things that are produced during the chemical reaction that you end with).

The numbers in front of each compound tell how many of molecules are involved for a full reaction without anything left over.  A "mol" is a large quantity ([tex]6.022*10^{23}[/tex]), in this case, of molecules , since it's unlikely you're only taking a single molecule of each substance (it would be so tiny, you wouldn't even know you were doing the reaction).

So,for every 2 moles of Magnesium used, we'll also need 1 mole of Oxygen, and it will produce 2 moles of Magnesium Oxide.

In a way, during the reaction it's almost like 2 moles of Magnesium is equal to 1 mole of Oxygen and is equal to 2 moles of Magnesium Oxide:

[tex]2 mol Mg(s)=1mol O_2(g)=2molMgO(s)[/tex]

From here, we can build some unit ratios, to convert between the known quantity of moles we have, and find the unknown quantity of moles that are requested.

We know that we are looking at 2.10 mol of Magnesium, so we want a unit ratio with moles of Mg on the bottom.  We want to find moles of O2, so we want a unit ratio of moles of O2 on top.

The unit ratio we want is the middle part of the equation, divided by the left part of the equation.

[tex]2 mol Mg(s)=1mol O_2(g)\\\frac{2 mol Mg(s)}{2 mol Mg(s)}=\frac{1mol O_2(g)}{2 mol Mg(s)}\\1=\frac{1mol O_2(g)}{2 mol Mg(s)}[/tex]

Since this quantity is 1, it is a unit ratio and can be multiplied to other things to change their units (for this problem).

Starting with what we know, and multiplying by our unit ratio:

[tex]2.10 mol Mg(s)*\frac{1mol O_2(g)}{2 mol Mg(s)}=1.05mol O_2(g)[/tex]

Notice that the units from the first quantity cancel with the units on the bottom of the fraction, leaving only the unit on top of the fraction ... the exact units we wanted!

So, 1.05mols of O2 would be consumed during the reaction if exactly 2.10moles of Magnesium are burned.

Answer: Understanding oxidation-reduction reactions

Explanation:

Rusting occurs when electrons are exchanged between iron and oxygen.

Answer:

N-Cl

Explanation:

Look at the chart below. Since N-Cl bond has a electronegativity difference of (3.0-3.0) zero, they are non-polar.

Answer:

.147 moles

Explanation:

PV = n RT        choose the correct "R"   to be 62.364  L torr /(K-mol)

   T  needs to be in K  (so add 273.15)

1351 torr  * 2 L  = n  * 62.364 * (21 + 273.15 )

solve for n = .147 moles

Answer:

92.9%

Explanation:

You have been given the actual yield of the reaction. First, you need to find the theoretical yield of the reaction. To do this, you need to (1) convert grams Fe₂O₃ to moles Fe₂O₃ (via molar mass from periodic table values), then (2) convert moles Fe₂O₃ to moles Fe (via mole-to-mole ratio from reaction coefficients), and then (3) convert moles Fe to grams Fe (via molar mass).

Once you have found the theoretical yield, you need to use the percent yield equation to calculate the final answer. This number should have 3 sig figs to match the given values.

(Step 1)

Molar Mass (Fe₂O₃): 2(55.845 g/mol) + 3(15.998 g/mol)

Molar Mass (Fe₂O₃): 159.684 g/mol

1 Fe₂O₃(s) + 3 CO(g) ---> 2 Fe(s) + 3 CO₂(g)

Molar Mass (Fe): 55.845 g/mol

50.0 g Fe₂O₃           1 mole              2 moles Fe           55.845 g
--------------------  x  ------------------  x  ---------------------  x  ----------------  = 35.0 g Fe
                               159.684 g         1 mole Fe₂O₃          1 mole

(Step 2)

                                 Actual Yield
Percent Yield  =  ---------------------------  x  100%
                             Theoretical Yield

                                32.5 g Fe
Percent Yield  =  ----------------------  x  100%  =  92.9%
                                35.0 g Fe

Answer:

The total number of electrons in a valence shell is called valence electrons. The electron configuration of rubidium shows that the last shell of rubidium has an electron. Therefore, the valence electrons of rubidium(Rb) are one.

Answer:

0.12 M

Explanation:

To find the new concentration, you need to (1) find the moles of Solution A (via the molarity equation), then (2) find the moles of Solution B, then (3) combine all of the moles and volumes, and then (4) calculate the new molarity. The final answer should have 2 sig figs to reflect the lowest amount of sig figs in the given values.

Solution A:

7.7 mL / 1,000 = 0.0077 L

Molarity = moles / volume

0.10 M = moles / 0.0077 L

0.00077 = moles

Solution B:

18.3 mL / 1,000 = 0.0183 L

Molarity = moles / volume

0.20 M = moles / 0.0183 L

0.00366 = moles

New Solution:

11.7 mL / 1,000 = 0.0117 L

New Volume = 0.0077 L + 0.0183 L + 0.0117 L

New Volume = 0.0377 L

New Moles = 0.00077 moles + 0.00366 moles

New Moles = 0.00443 moles

Molarity = moles / volume

Molarity = 0.0043 moles / 0.0377 L

Molarity = 0.1175 M = 0.12 M

P₄ + 10Cl₂ → 4PCl₅

mol P₄ = 455 : 123.895 g/mol = 3.672

mol Cl₂ = 10  x 3.672 = 36.72

mass Cl₂ = 36.72 x 71 g/mol = 2607.12 g

The 0.160 grams of Mg is equal to 0.00658 moles of Magnesium (Mg).

Given,

Mass of Mg, m=0.160g

The atomic mass of Mg is 24.31 g.

The number of moles can be represented as the ratio of the given mass of the atom/molecule to the Atomic/Molar mass of the atom/molecule.

Atomic mass can be defined as the mass of the one mole of an atom and Similarily, molecular mass can be defined as the mass of one mole of a molecule.

Number of moles, n=Given mass/Molar mass

n=0.160g/(24.31g/mol)=0.00658 moles

Hence, the 0.160 grams of Magnesium (Mg) is equal to 0.00658 moles of Magnesium (Mg).

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Answer:

[tex]\fbox {2 moles}[/tex]

Explanation:

Relation between grams of Carbon and moles :

[tex]\fbox {12 g Carbon = 1 mole}[/tex]

Multiply both sides by 2 :

⇒ 1 x 2 moles = 12 x 2 g

⇒ 2 moles = 24 g

Compared to infrared radiation, an electromagnetic wave that has a lower frequency will also have a longer wavelength and equal speed

Electromagnetic waves or EM waves are waves that are created as a result of vibrations between an electric field and a magnetic field.

It can be also defined as waves are composed of oscillating magnetic and electric fields.

One important feature fo electromagnetic radiation is that all have the same speed in vacuum, c, in vacuum, which is the speed of light.

Since, the speed, wavelength and frequency of the waves are related you can infere any of them when the other two are known.

The equation is:

speed = frequency × wavelength

   s     =          ν        ×      λ

   c     =          ν        ×      λ      . . . for the specific case of electromagnetic radiation

That inverse relation between frequency and wavelength, where the speed is the constant, shows that the lower the frequency the longer the wavelength.

Therefore,  the correct statment is that an an electromagnetic wave that has a lower frequency will also have a longer wavelength and equal speed (option B).

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Work arriving at total valence electrons are 24

The valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond

For a main-group element, a valence electron can exist only in the outermost electron shell; for a transition metal, a valence electron can also be in an inner shell.

Lewis structures, also known as Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDS), are diagrams that show the bonding between atoms of a molecule, as well as the lone pairs of electrons that may exist in the molecule.

Calculating the work arrival at total valence electrons

We know 1 bond contains

2 valence electrons

Here CCl4 contains 4 bonds that is 8 valence electrons

Therefore ,

Total valence electrons are 32

Now valence electrons remain after bond formation =

32 - 8

=24 valence electrons

A molecular model is a physical model of an atomistic system that represents molecules and their processes

Molecular image and lewis hand drawn structure is as shown below

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A chemical equilibrium when the amounts of reactants or products no longer change.

Explanation:

Chemical equilibrium is a dynamic process, meaning the rate of formation of products by the forward reaction is equal to the rate at which the products re-form reactants by the reverse reaction.

The moles of nitrogen produced is 0.40 moles of ammonia.

The Percent yield of ammonia is 81.2%

The moles of ammonia produced is obtained from the mole ratio of the reaction.

The mole ratio of hydrogen to nitrogen is 3 : 2

Based on the mole ratio, the limiting reactant is hydrogen.

Moles of nitrogen produced = 0.600 * 2/3 = 0.40 moles of ammonia.

mass of ammonia expected = 0.4 * 17 g = 6.8 g

Percent yield = 5.52/6.8 * 100% = 81.2%

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Answer:

a. Physical Chemistry

b.Organic Chemistry

c.Food analysis, a very important branch of analytical chemistry

d. Biochemistry

Explanation:

easy to compare

easy in calculation

adjust to units commonly used in certain places

The electroplating process of the coin results in the coating of the coin with copper metal.

Electroplating is the process of using coating the surface of a metal with another one electrolytic cell.

The electroplating of the coin is done using copper as the anode and the coin as the cathode. The electrolyte is copper sulfate solution.

Oxidation occurs at the anode with the copper metal being converted to copper (ii) ions.

Reduction occurred at the cathode as the copper (ii) ions in the solution accept electrons to become copper metal and the coin being coated with copper.

The half-reactions are shown below:

At the anode:

[tex]Cu(s) \rightarrow Cu^{2+}(aq) + 2e^{-}[/tex]

At the cathode:

[tex]Cu^{2+}(aq) + 2e{-} \rightarrow Cu(s)[/tex]

Therefore, the electroplating process of the coin results in the coating of the coin with copper metal.

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The types of bonds and atoms in the molecule shown below are C. Single bonds, double bonds, carbon atoms, and hydrogen atoms.

Carbon can only form a bond with a maximum of 4 other molecules.

We have been given a molecule

H₂C               CH₂-CH3

       C=C

H                H

In the given figure we can see that the molecule includes one double bond and other are single bonds.

Thus, The types of bonds and atoms in the molecule shown below are C. Single bonds, double bonds, carbon atoms, and hydrogen atoms.

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.

Which buffer can be suitable to prepare a solution that needs to be buffered at pH 4? Explain your

choice.

A. Formic acid/Formiate buffer

B. Carbonic acid/Bicarbonate buffer

C. Ammonia/Ammonium buffer

D. Any buffer will work.

E. None of the buffers will be suitable.

34 Which of the following will form a buffer when mixed together? Explain a weak acid/base and its conjugate base/acid in the form of salt

Answer: A representative particle can be an atom, and an ion. a molecule, or a formula unit.

Explanation:

A representative particle is the smallest unit in which a substance naturally exists. For the majority of elements, the representative particle is the atom. Iron, carbon, and helium consist of iron atoms, carbon atoms, and helium atom, respectively.

Radon is a naturally occurring radioactive gas that is odorless and tasteless.

Atoms-the smallest particle of an element

Ions-atoms with positive or negative charges.

Molecules- two or more covalently bonded atoms.

Formula units- the simplest ratio of ions that make up an ionic compound.

The statement which is not true is as follows:

Thus, the correct option is C.

An equilibrium may be defined as the condition in which both the reactants and products are present in concentrations that have no additional propensity to alter with time so that there is no noticeable transformation in the possessions of the system.

The causation of repulsive force was thought to be made by the overlap of atomic orbitals and in between the electrons of diverse atoms, it matters a lot.

The equilibrium distance between nuclei of two covalently bonded atoms is called the bond length of that atom. It is the atomic separation at equilibrium.

Equilibrium occurs when the attractive and repulsive forces neglected the effect of each other in a specific state.

Therefore, it is well described above.

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Answer:

Boron, Hydrogen, Helium, Lithium, Beryllium, Carbon, Nitrogen, Oxygen, etc.

Explanation:

These are all elements, not all of them.

Answer:

Place 20.0 g NaOH(s) in a flask and dilute to 1.00 L with water.

Explanation:

Answer:

okay

Explanation:

9 . acidic

10.  hydrogen

answer the following questions

11. Gold as a precious metal is used widely in making jewelry items. This metal is preferred over others for jewelry pieces for various reasons. One important reason for its popularity is that it does not react with atmospheric moisture and therefore, it does not rust.

12. corrosion is defined as rust it's due to humidity and moisture

13. Sulphur appears much below chlorine in the reactivity table and cannot displace chlorine from dilute HCl.

14. Highly conductive metal

Surpassed only by silver, copper is a highly conductive metal. This means electricity can pass through it with greater ease, making it ideal for use in electrical wires. Companies can use other conductive metals to create electrical wires.

15. Corrosion

Copper metal when exposed to air turns green in color due to corrosion. When the copper vessel is exposed to air in the rainy season, the metal reacts with gases, moisture, and atmospheric gases to form a mixture of copper carbonate and copper hydroxide. This gives a green color to the surface of the copper meta

16. Silicon

silicon is the backbone of the electronics industry. Because silicon is the reason for the fast development happened in the field of electronics. therefore, silicon is the backbone of electronics.

17. High chemical reactivity

Sodium is stored under kerosene because of its high chemical reactivity with almost all of the other elements (for example oxygen from the air which oxidizes it instantly). Kerosene and mineral oil are the only chemicals that make sodium inert. Usually, when Na reacts with a solvent it liberates hydrogen gas from its composition.

18. Metal oxides are oxides of metals. Nonmetal oxides are oxides of nonmetals. The main difference between metal oxides and nonmetal oxides is that metal oxides are basic compounds whereas nonmetal oxides are acidic compounds.

19.  Silver is more likely to tarnish near a petroleum refinery than in a place far away from it because when silver reacts with petroleum or hydrogen sulfide present in it as a pollutant in the air, it starts forming a black coating of silver sulfide.

20. A noble metal is ordinarily regarded as a metallic chemical element that is generally resistant to corrosion and is usually found in nature in its raw form. Gold, platinum, and the other platinum group metals (ruthenium, rhodium, palladium, osmium, iridium) are most often so classified. Silver, copper, and mercury are less often to sometimes included as noble metals although each of these usually occurs in nature combined with sulfur.

The value of delta H° for aniline = 6415 Kj/mol

calculation

Step 1: find heat

Q (heat)  =  C (specific heat capacity)  x ΔT (change in temperature)

C= 4.25 kj/c°

ΔT = 69.8-29.5  = 40.3 c°

Q= 4.25 kj/c  x  40.3 c = 171.28 kj

Step 2:  find the moles of aniline

moles  = mass/molar  mass

= 2.49 g/ 93.13 g/mol =0.0267 moles

Step 3:  find delta H

171.28 kj/0.0267 mol = 6415 kj/mol

since the reaction is  exothermic  delta H = 6415 Kj/mol

Answer:

-6.41x10^3

Explanation:

2.49 is 3 significant figures, so your answer should reflect that. Since heat is lost to the surroundings, the reaction is exothermic, and the answer should be negative.

Answer: Double replacement reaction

Explanation:

Answer:

Explanation:Hyaluronic acid is a natural substance found in the fluids in the eyes and joints. It acts as a cushion and lubricant in the joints and other tissues.

Different forms of hyaluronic acid are used for cosmetic purposes. Hyaluronic acid might also affect the way the body responds to injury and help to decrease swelling.

Hyaluronic acid injections are US FDA-approved for several conditions, including cataracts, osteoarthritis, and as an injectable gel filler (Juvedérm) for facial wrinkles. People also commonly take hyaluronic acid by mouth and apply it to the skin for UTIs, acid reflux, dry eyes, wound healing, aging skin, and many other conditions, but there is no good scientific evidence to support most of these other uses.

How does it work ?

Uses & Effectiveness ?

Likely Effective for

Cataracts. Injecting hyaluronic acid into the eye is effective when used during cataract surgery by an eye surgeon.

Swelling (inflammation) and sores inside the mouth (oral mucositis). Applying an FDA-approved hyaluronic acid gel is effective for treating mouth sores. It's not clear if other products help.

Answer:

Explanation:

Hyaluronic acid is a natural substance found in the fluids in the eyes and joints. It acts as a cushion and lubricant in the joints and other tissues. Different forms of hyaluronic acid are used for cosmetic purposes. Hyaluronic acid might also affect the way the body responds to injury and help to decrease swelling.

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