If it requires 45.8 cal to melt 8.4 g of a substance, what is the heat of
fusion of the substance?

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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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:

Density = 0.0035 g/cm³

Explanation:

The density equation looks like this:

Density (g/cm³) = mass (g) / volume (cm³)

You have been given both the mass and volume. However, the given volume is not in the correct units. To convert cm to cm³, you should simply raise the given volume to the power of 3.

24 cm  =  (24 cm)³  =  24³cm³  =  13,834 cm³

Now, you can plug you mass and volume into the equation and solve for density. The final answer should have 2 sig figs to reflect the given values.

Density = mass / volume

Density = 48 g / 13,824 cm³

Density = 0.00347 g/cm³

Density = 0.0035 g/cm³

121 g [tex]AlI_{3}[/tex] aluminum iodide, from the complete reaction of 113 grams I₂ according to the following balanced chemical equation:

2Al(s) + 3I₂(s) → 2[tex]AlI_{3}[/tex]

As per the given balanced equation,

3 moles of [tex]I_{2}[/tex] are used to give 2 moles of [tex]AlI_{3}[/tex].

Atomic weight of iodine is 127 gm/ mole

So, molecular weight of iodine molecule = 254 gm/ mole

There for , we can say that 1 mole o iodine molecule contain 254 g

So ,Given 113 gm iodine contains how many moles?

  Moles of iodine = 113/254 = 0.44 moles

from the equation we can say that 3 moles of iodine used to give 2 moles of aluminum iodide.

So, 0.44 moles of iodine gives how many moles of aluminum iodide ?

   Moles of aluminum iodide = 0.44 × 2 ÷  3

                                             = 0.2965 moles

Molecular weight of one mole of aluminum iodide = atomic weight of Al + 3( atomic weight of iodine )

      = 408 gm

∴ 1 mole of aluminum iodide = 408 gm

so, 0.2965 moles of aluminum iodide = ?

            = 0.2964 × 408

            = 121 gm  Aluminum iodide formed.

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Answer:

true is correct

Polyester and Nylon are examples of synthetic materials called polymers. This statement is True.

Polymers are large molecules composed of repeating subunits called monomers, which are chemically bonded together. In the case of polyester, it is made from a polymer called polyethylene terephthalate (PET), while Nylon is made from polyamide monomers. These polymers are created through polymerization processes that combine smaller molecules to form long chains.

Synthetic polymers like polyester and nylon are widely used in various applications due to their desirable properties, such as strength, durability, and resistance to chemicals and moisture.

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Answer:

(a) 1s2 2s1

Explanation:

Electron configurations of atoms are in their ground state when the electrons completely fill each orbital before starting to fill the next orbital.

It's important to know how to read and interpret the notation.

For example, the first part of option (a) says "1s2"

It important to know which orbitals are in each shell:

So, it's also important to know how many electrons can be in each orbital in order to know if they are full or not.  The electrons should fill up these orbitals for each level, in this order:

For option (a):

This is in it's ground state.

For option (b):

Because the 3s orbital has an electron, but the lower 2p before it isn't full.  This is NOT in it's ground state.

For option (c):

Although the 2p orbital is full, since the 2s orbital before it was not yet full, this is NOT in it's ground state.

For option (d):

Again, despite that the final orbital (in this case, the 2s orbital), is full, since the 1s orbital before it was not yet full, this is NOT in it's ground state.

6.349 g mass of anhydrous magnesium sulfate will remain.

A mole is defined as 6.02214076 × 1023 of some chemical unit, be it atoms, molecules, ions, or others. The mole is a convenient unit to use because of the great number of atoms, molecules, or others in any substance.

Molar mass MgSO₄.7 H₂O = 246.52 g/mol

[tex]Moles =\frac{mass}{molar \;mass}[/tex]

[tex]Moles =\frac{13.0 g}{246.52}[/tex]

0.0527 moles

Molar mass MgSO₄ = 120.4 g/mol

Mass of anhydrous magnesium sulfate :

( 0.0527 x 120.4 ) => 6.349 g

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Answer:

less HCL acid is required to neutralize a weaker solution of base (sodium bicarbonate).

Explanation:

Answer: c) [tex]2\text{Na}_{3}\text{PO}_{4}+3\text{CaCl}_{2} \longrightarrow 6\text{NaCl}+\text{Ca}_{3}\text{(PO}_{4})_{2}[/tex]

The volume of the balloon when the mass of oxygen gas is decreased to 50g is 50L.

We will use the ideal gas equation-

PV=nRT

P=Pressure

V=volume

n=no. of moles

T=temperature

In this question temperature and pressure will remains constant then the above equation can be rewritten as-

[tex]V_{1} /n_{1} =V_{2} /n2[/tex]

where V1= initial volume of the balloon

            V2=  volume of the balloon when the mass of oxygen gas is decreased to 50g

now, substitute the values in the above equation-

       100/3.12=V2/1.56

hence, the volume of the balloon when the mass of oxygen gas is decreased to 50g is 50L.

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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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The pH can be obtained directly from the concentration using the formula below pH = - log [H⁺]  Hence, pH of a 8.4x10⁻⁶ M H⁺ solution is 5.08.

A figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid and higher values more alkaline.

Taking the negative logarithm of the concentration of hydronium ions that are in the solution:

pH = - log [H⁺]

     = - log [8.4x10⁻⁶ ]

     =  5.08

Hence, pH of a 8.4x10⁻⁶ M H⁺ solution is 5.08.

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Answer:

= 64584.7176 g

or

= 64.5847 kg

Explanation:

From our question, we have been asked to find the mass of SO₂ containing 6.075 × 10^26 S atoms.

We know that from Avogadro's constant,

1 mole of a substance contains 6.02 x 10²³ ions/atoms/units

Thus,

1 mole => 6.02 x 10²³ atoms

x moles=> 6.075 × 10²⁶ atoms

We cross multiply;

x moles = (6.075 × 10²⁶ x 1)/(6.02 x 10²³)

= 1009.1362 moles

1 mole of SO2 = 64 g

1009.1362 moles = ?

=>

[tex] \frac{1009.1362 \times 64}{1} [/tex]

= 64584.7176 g

= 64.5847 kg

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.

You would have to fix the tilt of the Moon's orbit and make the Moon orbit planet Earth within the same plane that the Earth orbits the Sun.

A lunar eclipse can be defined as a phenomenon which occurs when the planet Earth comes in between the Moon and the Sun, thereby causing the Earth to cover the Moon with its shadow.

In order to have a lunar eclipse occur every month, you would have to fix the tilt of the Moon's orbit and make the Moon orbit planet Earth within the same plane that the Earth orbits the Sun, so as to block any ray of sunlight from reaching the Moon.

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160 g of SO3 are needed to make 400 g of 49% H2SO4.

The equation of the reaction for the formation of H2SO4 from SO3 is given below as follows:

[tex]SO_{3} + H_{2}O \rightarrow H_{2}SO_{4}[/tex]

1 mole of SO3 produces 1 mole of H2SO4

Molar mass of SO3 = 80 g/mol

Molar mass of H2SO4 = 98 g/mol

80 g of SO3 are required to produce 98 og 100%H2SO4

mass of SO3 required to produce 400 g of 100 %H2SO4 = 80/98 × 400 = 326.5 g of SO3

Mass of SO3 required to produce 49% of 400 g H2SO4 = 326.5 × 49% = 160 g

Therefore, 160 g of SO3 are needed to make 400 g of 49% H2SO4.

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Sucrose doesn't show appreciable dissociation in water, so i≈1 in this case. by extension, −7.3°C is the approximate freezing point of this solution.

The temperature at which a liquid solidifies.

Sucrose doesn't show appreciable dissociation in water, so i≈1 in this case. by extension, −7.3°C is the approximate freezing point of this solution.

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Simplified concentration

[tex]\\ \rm\Rrightarrow 1.13\times 10^{-2}M[/tex]

Now

[tex]\\ \rm\Rrightarrow pH=-log[H^+][/tex]

[tex]\\ \rm\Rrightarrow pH=-log(1.13\times 10^{-2})[/tex]

[tex]\\ \rm\Rrightarrow pH=-log1.13-log10^{-2}[/tex]

[tex]\\ \rm\Rrightarrow pH=-0.05+2[/tex]

[tex]\\ \rm\Rrightarrow pH=1.95[/tex]

Highly acidic

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.

Answer:

4Al +3O₂ → 2Al₂O₃

Explanation:

To balance the chemical equation, start by identifying the number of atoms of each element on both sides of the equation.

Al +O₂ → Al₂O₃

Reactants (right-hand side of the arrow)

Al➭ 1

O➭ 2

Products (left-hand side of the arrow)

Al➭ 2

O➭ 3

Balancing the equation means that we need to ensure the number of atoms of each element is the same on both sides of the equation.

Let's balance the number of O atoms.

Al +3O₂ → 2Al₂O₃

Reactants

Al➭ 1

O➭ 3(2)= 6

Products

Al➭ 2(2)= 4

O➭ 2(3)= 6

Balancing the number of Al atoms:

4Al +3O₂ → 2Al₂O₃

Reactants

Al➭ 4

O➭ 6

Products

Al➭ 4

O➭ 6

The equation is now balanced.

Additional:

For a similar question on balancing equations, do check out the following!

Mendeleev positioned elements in the periodic table in increasing order of their atomic numbers, such that elements having identical chemical properties and characteristics plunge into the same group.

Mendeleev's periodic table may be defined as a collection of elements in an increasing atomic mass hierarchy in a table arrangement, such that it reminisces resemblances and manias according to their chemical properties and characteristics.

Mendeleev found that two elements existed between atomic weights 65.2 and 75 because he comprehended especially pleasingly that the possessions of the elements were more comparable and closer to this degree.

He also anticipated having other elements that would have their possessions comparable to these other elements.

Therefore, he departed a void for these two elements in the periodic table until they were ultimately found in their real existence.

The complete question is as follows:

Look at the two question marks between zinc (Zn) and arsenic (As). At the time, no elements were known with atomic weights between 65.2 and 75. But Mendeleev predicted that two elements must exist with atomic weights in this range. What led Mendeleev to predict that two undiscovered elements existed in that range?

Therefore, it is well described above.

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Answer:

c, have no internal energy

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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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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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 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.

Electrochemical cell is one in which energy is released by a chemical action.

An electrochemical cell is one in which energy is released by a chemical action.

Now we have the reaction;

Zn^2 (aq) + 2e- = Zn(s)

Pb²(aq) + 2e- → Pb(s)

and

Cr2O7 + 14H + 6e- 2Cr³+ 7H₂O

H₂O2 + 2H+ + 2e- →2H₂O

In the first case, the Ecell is obtained from;

(-0.13 V) - (-0.76 V)

= 0.63 V

In the second case;

1.78 V - 1.33 V

= 0.45 V

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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.