A balloon containing helium gas expands from 230
mL to 860 mL as more helium is added. What was
the initial quantity of helium present if the
expanded balloon contains 3.8 x 10-4 mol,
assuming constant temperature and pressure?
Which of the variables are known?
DONE

Answer:

M = 16.8 M

Explanation:

Data: HNO3

moles = 12.6 moles

solution volume = 0.75 L

Molarity is represented by the letter M and is defined as the amount of solute expressed in moles per liter of solution.

[tex]M=\frac{moles}{solution volume}[/tex]

The data is replaced in the given equation:

[tex]M=\frac{12.6 mol}{0.75L}=16.8\frac{mol}{L}[/tex]

Answer:

The correct answer is 16.8 M

Explanation:

The molarity (M) of a solution is the number of moles of solute in 1 liter of solution. The HNO₃ solution contains 12.6 moles of solute (in this case the solute is HNO₃) in 0.75 liters. In order to find the molarity, we have to divide the number of moles into the volume in liters as follows:

M = 12.6 moles/0.75 L = 16.8 moles/L = 16.8 M

Answer:

There are 0.100 moles chlorine ions (Cl-) involved

Explanation:

Step 1: Data given

Volume of CaCl2 = 25.0 mL = 0.025 L

Molarity of CaCl2 = 2.00 M

Step 2: The balanced equation

CaCl2 (aq) + 2AgNO3 (aq) ⇆ Ca(NO3)2 (aq) + 2AgCI (s)

CaCl2 → Ca^2+ + 2Cl-

Step 3: Calculate moles CaCl2

Moles CaCl2 = molarity CaCl* volume

Moles CaCl2 = 2.00 M * 0.025 L

Moles CaCl2 = 0.050 moles

Step 4: Calculate moles chloride ions

CaCl2 → Ca^2+ + 2Cl-

For 1 mol CaCl2 we have 1 mol Ca^2+ and 2 moles Cl-

Moles Cl- ions = 2*0.050 moles

Moles Cl- ions = 0.100 moles

There are 0.100 moles chlorine ions (Cl-) involved

The reaction of 25.0 mL of a 2.00 M CaCl2 solution provides 0.100 moles of chloride ions for the reaction, based on the stoichiometry that shows each mole of CaCl2 gives two moles of chloride ions.

To calculate how many moles of chloride ions were involved in the reaction where 25.0 mL of a 2.00 M CaCl2 solution is used, we must first understand the stoichiometry of the reaction:

CaCl2(aq) + 2AgNO3(aq) → Ca(NO3)2(aq) + 2AgCl(s)

From the balanced equation, we see that each mole of CaCl2 provides two moles of Cl− ions. To find the moles of CaCl2, we use the concentration and volume of the solution:

(2.00 moles/L) × (0.025 L) = 0.050 moles of CaCl2

Since there are two moles of Cl− for every mole of CaCl2, we multiply the moles of CaCl2 by 2:

0.050 moles × 2 = 0.100 moles of chloride ions

Answer:

0.178 moles of oxygen gas molecules were collected.

Explanation:

Pressure at which oxygen gas collected = p= 1.00 atm

Vapor pressure of the water [tex]p'=34.5 Torr=\frac{34.5}{760} atm=0.0454 atm[/tex]

Pressure of the oxygen gas = P

p = p' + P

[tex]1.00 atm =0.0454 atm+P[/tex]

P = 1.00 atm -  0.0454 atm = 0.9546 atm

Volume of the oxygen gas = V = 4.56 L

Moles of oxygen gas = n

Temperature at which gas collected = T = [tex]25^oC=273+25=298 K[/tex]

[tex]PV=nRT[/tex] (ideal gas)

[tex]n=\frac{PV}{RT}=\frac{0.9546 atm\times 4.56 L}{0.0821 atm L/mol K\times 298 K}=0.178 mol[/tex]

0.178 moles of oxygen gas molecules were collected.

Answer:

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Explanation:

Answer:

1,3,6

Explanation:

Answer:

1,3,6

Explanation:

Answer : The correct option is, (C) C to Fe

Explanation :

The given chemical reaction is:

[tex]2Fe_2O_3+3C\rightarrow 4Fe+3CO_2[/tex]

By the stiochiometry we can say that, 2 moles of [tex]Fe_2O_3[/tex] react with 3 moles of C to gives 4 moles of Fe and 3 moles of [tex]CO_2[/tex].

From the balanced chemical reaction we conclude that,

As, 3 moles of C produces 4 moles of Fe

So, 1 mole of C produces [tex]\frac{4}{3}[/tex] moles of Fe

That means, the moles of ratio of C to Fe is 4 : 3

Therefore, the correct option is (C) C to Fe

To calculate the pH of a 0.107 M NaHA solution, where HA is part of a diprotic acid with given Ka values, HA^-− dissociates in water according to its first ionization step. The pH is determined using the Ka1 value and is calculated to be approximately 1.80.

To calculate the pH for a 0.107 M solution of NaHA, where HA is a diprotic acid (H2A), given Ka1 = 2.3× 10–4 and Ka2 = 3.0× 10–12, we first need to consider what happens when NaHA dissolves in water.

NaHA will dissociate to form NA+ and HA−. Since the concentration of NaHA is relatively high and Ka1 is significantly greater than Ka2, we can assume that the HA− will primarily dissociate according to the first ionization step, while the second ionization can be neglected in this approximation.

The ionization can be represented as:
HA−(aq) + H2O(l) → A2−(aq) + H3O+(aq).

Writing the expression for Ka1 we have:
Ka1 = [H3O+][A2−]/[HA−].
Assuming that [H3O+] = [A2−], we can simplify this to:
Ka1 = [H3O+]^2/[HA−].

Rearranging and solving for [H3O+], we get:
[H3O+] = √(Ka1 × [HA−]). Substituting the given values in:
[H3O+] = √(2.3× 10–4 × 0.107) = √(2.461× 10–4) ≈ 1.57× 10–2.

Using the formula for pH, pH = -log[H3O+], we find:
pH = -log(1.57× 10–2) ≈ 1.80.

Thus, the pH of the 0.107 M NaHA solution is approximately 1.80.

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The pH of a 0.107 M solution of NaHA, derived from the diprotic acid H₂A, is calculated to be approximately 6.24.

To calculate the pH of a 0.107 M solution of NaHA, a salt derived from the diprotic acid H₂A, we will consider that NaHA will primarily exist as HA⁻ in the solution. This involves both the first and second ionization constants of the diprotic acid.

Given:

Step-by-step calculation:

Ka₂ = [H⁺][A²⁻] / [HA⁻]

Assume the initial concentration of HA⁻ is approximately equal to the initial concentration of NaHA (0.107 M) as the dissociation is minimal. Let the change in concentration be 'x.'

Hence:

Ka₂ = 3.0 × 10⁻¹² = (x)(x) / (0.107 - x) ≈ x² / 0.107

Solving for 'x':

x = [H⁺] = √(Ka₂ × 0.107) = √(3.0 × 10⁻¹² × 0.107) ≈ 5.7 × 10⁻⁷ M

pH = -log[H⁺] = -log(5.7 × 10⁻⁷) ≈ 6.24

Therefore, the pH of a 0.107 M solution of NaHA is approximately 6.24

Answer:

The air pressure is significantly less than 1 atm, so the boiling point of water is much lower than at sea level.

Explanation:

This has to do with Gay Lussac's Law (a.k.a pressure law) which in essence means that when pressure goes up, temperature goes up and when pressure decreases, temperature decreases. This is why when the air pressure is signifcantly less than 1 atm (the pressure at sea level), the boiling point of water is much lower than at sea level.

The best explanation for the scenerio is :  High in the mountains , the air pressure is significantly less than 1 atm, so the boiling point if water is much lower than at sea level.

The higher you go above sea level the lower the air pressure and this will significantly affect the temperature at which certain liquids ( water ) will boil. therefore the boiling point of water will be  much lower than at sea level.

In this scenerio the application of Gay Lussac's law comes in

Gay Lussac's law states that the pressure of gas is directly proportional to its temperature at constant volume

Hence we can conclude that The best explanation for the scenerio is :  High in the mountains , the air pressure is significantly less than 1 atm, so the boiling point if water is much lower than at sea level.

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Answer:

For the first one it is x=π/3+2πn and 2π/3+2πn and for the second one it is π/2

Explanation:

If the water molecule was linear instead of bent the water would no longer produce hydrogen bonds.

Explanation:

Answer:

2 and 3 are correct

Explanation:

Answer: The change in entropy that occurs in the system is 36.3 J/Kmol

Explanation:

Given : 1 mole of isopropyl alcohol gives heat = 5.37 kJ

Thus 1.24 moles of isopropyl alcohol gives heat = [tex]\frac{5.37}{1}\times 1.24=6.66 kJ[/tex]

To calculate the temperature , we use the equation:

[tex]\Delta S_f=\frac{\Delta H_{f}}{T}[/tex]  

where,  

[tex]\Delta S_f[/tex] = Entropy of fusion = ?

[tex]\Delta H_{f}[/tex] = enthalpy of fusion  = 6.66 kJ/mol = 6660 J/mol     (1kJ=1000J)

T = melting point = [tex]-89.5^0C=(273-89.5)K=183.5K[/tex]

[tex]\Delta S_f=\frac{6660J/mol}{183.5K}=36.3J/Kmol[/tex]

Thus the change in entropy that occurs in the system is 36.3 J/Kmol

Answer:

Explanation:

Chlorite anion, ClO₂⁻ has one atom of chlorine and two atoms of oxygen.

Chlorine atom has 7 valence electrons (group 17 of the periodic table) and oxygen has 6 valence electrons (group 16 of the periodic table).

Thus, in total the anion has 7 + 6×2 electrons, plus an additional electron indicated by the negative charge of the anion: 7 + 12 + 1 = 20 valence electrons, that must be distributed among the three atoms.

Being chlorine the most electronegative atom, you place it in the center. surrounded by the two oxygen atoms.

Thus, so far:

             O Cl  O (pending to place the valence electrons.

You can put two electrons between each chlorine and oxygen atoms to form the bonds:

     O : Cl : O

Also, complete the octets:

 . .      . .    . .

: O  :  Cl :  O :

 . .     . .     . .

That structure works because:

But you need to calculate the formal charges on each atom:

For chlorine:

For each oxygen:

The total charge of the anion is +1 -1 - 1 = -1.

And the complete structure with the charge is:

   . .      . .    . .

[ : O  :  Cl :  O : ] ⁻

   . .      . .     . .

The square bracketts comprise the entire anion and the negative charge is for the entire structure.

In this structure, the central atom (Cl) is surrounded by two bonding and two unshared pairs of electrons. (this is the answer to the question).

There is another structure which minimizes the formal charge, which will be preferred. It is by making a double bond between chlorine and one of the oxygen atoms, by moving two of the atoms beside one chlorine.

That structure is:

 . .      . .    . .

: O  :  Cl ::  O

 . .     . .     . .

There you have 20 valence electrons and complete octets too, but the formal charges are:

Chlorine:

The oxygen on the left is equal to the previous structure, thus - 1 forma charge.

The oxygen on the right:

Hence, this las structure minimizes the formal charges and is preferred.

This is:

 . .      . .    . .

: O  :  Cl ::  O

 . .     . .     . .  

But you must add the negative charge which belongs to the complete anion:

      . .      . .     . .

[     : O  :  Cl ::  O  ] ⁻

      . .     . .      . .

The square brackets comprise the entire anion and the negative charge is for it.

Hence, in this other structue the central atom, chlorine, is surrounded by six bonding electrons and four nonbonding electrons.

Explanation:

the answer and explanation is in the picture

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A student finds that 4700 J of heat are required to raise the temperature of 250.0 g of metal X from 22°C to 63°C. 0. 459J/g/C  is the identity of metal X.

The amount of heat required to raise the temperature of one gram of a substance by one Celsius degree is defined as specific heat.

Heat capacity, also known as specific heat, is the amount of heat required per unit mass to raise the temperature by one degree Celsius.

Specific heat is useful in determining processing temperatures and the amount of heat required for processing, as well as in distinguishing between two polymeric composites.

The specific heat capacity of a substance is typically determined by measuring the heat capacity of a sample of the substance, usually with a calorimeter, and dividing by the sample's mass.

Given:

Heat = 4700 J

M = 250.0 g

T = 63 - 22 = 41°C

4700 = 250 ×C× 41

4700 = 10250 × C

C = 459J/g/C

Thus, A student finds that 4700 J of heat are required to raise the temperature of 250.0 g of metal X from 22°C to 63°C. 0. 459J/g/C  is the identity of metal X.

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Answer: The moles of nickel (II) chloride were present in the solution are 0.925

Explanation:

Molarity is defined as the number of moles of solute dissolved per liter of the solution.

[tex]Molarity=\frac{n}{V_s}[/tex]

where,

Molarity = 0.925

n= moles of solute  = 0.2

[tex]V_s[/tex] = volume of solution in L = 1.0 L

Now put all the given values in the formula of molarity, we get

[tex]0.925=\frac{moles}{1.0L}[/tex]

[tex]moles=0.925\times 1.0=0.925[/tex]

Therefore, the moles of nickel (II) chloride were present in the solution are 0.925

Answer:

Option D. 1.40x10^5g

Explanation:

From Avogadro's hypothesis, we understood that 1 mole of any substance contains 6.02x10^23 particles. This equally means that 1mole of Cl2 contains 6.02x10^23 particles.

1 mole of Cl2 =2 x 35.5 = 71g.

Now, If 71g of Cl2 contains 6.02x10^23 particles,

Then Xg of Cl2 will contain 1.19x10^27 particles i.e

Xg of Cl2 = (71x1.19x10^27)/(6.02x10^23)

Xg of Cl2 = 1.40x10^5g

Therefore, 1.40x10^5g of Cl2 contain 1.19x10^27 particles

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Answer:A

Explanation:Henry’s Law

Final answer:

Pressure has very little effect on the solubility of solids or liquids, but has a significant effect on the solubility of gases.

Explanation:

Pressure has very little effect on the solubility of solids or liquids, but has a significant effect on the solubility of gases. Gas solubility increases as the partial pressure of a gas above the liquid increases. For example, when carbonated beverages are packaged, they are done so under high CO₂ pressure so that a large amount of carbon dioxide dissolves in the liquid. When the bottle is open, the equilibrium is disrupted because the CO₂ pressure above the liquid decreases, causing bubbles of CO₂ to rapidly exit the solution and escape out of the top of the open bottle.

Answer:

The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance

Explanation:

To determine the average atomic mass, we require abundance of every isotope in the nature.

Average atomic mass is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Final answer:

The balanced chemical equation for the reaction between fluorine gas and aqueous iron (II) iodide is F₂ + 2 FeI₂ → 2 FeF₂ + I₂, indicating the direct combination of these substances to form new products.

Explanation:

The reaction between fluorine gas and aqueous iron (II) iodide to produce aqueous iron (II) fluoride and iodine liquid can be represented as a balanced chemical equation. When writing a balanced chemical equation, it is vital to ensure that the number of atoms of each element on the reactants side is equal to the number of atoms of that element on the products side, adhering to the law of conservation of mass.

The correct balanced chemical equation for this reaction is:

F₂ + 2 FeI₂ → 2 FeF₂ + I₂

Here, one mole of fluorine gas reacts with two moles of iron (II) iodide to produce two moles of iron (II) fluoride and one mole of iodine.

Answer : The partial pressure of [tex]H_2[/tex] at equilibrium is, 1.0 × 10⁻⁶

Explanation :

The partial pressure of [tex]HBr[/tex] = [tex]1.0\times 10^{-2}atm[/tex]

The partial pressure of [tex]H_2[/tex] = [tex]2.0\times 10^{-4}atm[/tex]

The partial pressure of [tex]Br_2[/tex] = [tex]2.0\times 10^{-4}atm[/tex]

[tex]K_p=4.2\times 10^{-9}[/tex]

The balanced equilibrium reaction is,

                                [tex]2HBr(g)\rightleftharpoons H_2(g)+Br_2(g)[/tex]

Initial pressure    1.0×10⁻²       2.0×10⁻⁴      2.0×10⁻⁴

At eqm.            (1.0×10⁻²-2p)   (2.0×10⁻⁴+p)  (2.0×10⁻⁴+p)

The expression of equilibrium constant [tex]K_p[/tex] for the reaction will be:

[tex]K_p=\frac{(p_{H_2})(p_{Br_2})}{(p_{HBr})^2}[/tex]

Now put all the values in this expression, we get :

[tex]4.2\times 10^{-9}=\frac{(2.0\times 10^{-4}+p)(2.0\times 10^{-4}+p)}{(1.0\times 10^{-2}-2p)^2}[/tex]

[tex]p=-1.99\times 10^{-4}[/tex]

The partial pressure of [tex]H_2[/tex] at equilibrium = (2.0×10⁻⁴+(-1.99×10⁻⁴) )= 1.0 × 10⁻⁶

Therefore, the partial pressure of [tex]H_2[/tex] at equilibrium is, 1.0 × 10⁻⁶

Answer: 4M

Explanation:

Explanation:

A non-renewable energy source (also called a finite source) is a natural resource that cannot be readily replaced by natural means at a quick pace enough to keep up with consumption.

An example is a carbon-based fossil fuel.

Answer:

C. An energy source that cannot be reused or replaced

Explanation:

non-renewable = cannot be renewed

Answer: nuclear

Explanation:

Nuclear energy resource causes the most safety concerns. Therefore, option C is correct.

Nuclear energy is the energy contained within an atom's nucleus, or core. Nuclear energy can be used to generate electricity, but it must be liberated from the atom first.

Nuclear power is a zero-emission source of clean energy. Fission, the process of splitting uranium atoms to produce energy, is used to generate power. The heat produced by fission is used to generate steam, which spins a turbine to generate electricity without emitting the harmful byproducts that fossil fuels do.

Coal, oil, and gas are by far the most significant contributors to global climate change, accounting for more than 75% of global greenhouse gas emissions and nearly 90% of total carbon dioxide emissions.

Thus, option C is correct.

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Answer:

The goal is to remove both heavy solids and floating oils

Explanation:

Primary treatment consists of temporarily holding the sewage in a quiescent basin where heavy solids can settle to the bottom while oil, grease and lighter solids float to the surface. The settled and floating materials are removed and the remaining liquid may be discharged.

Answer:

178.98 sq. feet

Explanation:

The path and the garden has been shown in the figure below. The green area is the garden and the area in brown is the path.

It has been given that,

Radius of garden = 8 feet

So, the area of garden = 3.14 × 8 × 8 = 200.96 sq. feet

The total radius of the land including garden and path = 8 + 3 = 11 feet

So, the total are of land including garden and path = 3.14 × 11 × 11 = 379.94 sq. feet

So, the area of path = Total area of the land - area of garden

Area of path = 379.94 - 200.96 = 178.98 sq. feet

Answer:

c 178.98 ft

Explanation:

Covalent network solids often have the highest melting points. These solids are characterized by a network of covalent bonds that extend throughout the material, creating a very stable and strong structure.

Materials with high melting points typically have strong intermolecular forces. In the case of covalent network solids, such as diamond (pure carbon) or silicon carbide, each atom is bonded to several others in a lattice structure, creating an incredibly strong bond throughout the entire structure. This extensive network of strong bonds requires a large amount of energy to break apart, thus resulting in very high melting points. Molecular solids, where molecules are held together by weaker forces such as van der Waals forces, generally have much lower melting points because these intermolecular forces are much easier to overcome. Ionic solids also have high melting points, but not typically as high as covalent network solids, due to the nature of ionic bonds which are strong, but localized between individual pairs of ions rather than throughout the entire structure.

The rate of effusion of gas B is 728.32 m/s

Explanation:

Given:

Mass of A, m₁ = 46 g/mol

Rate of effusion of A, R₁ = 515 m/s

Mass of B, m₂ = 92 g/mol

Rate of effusion of B, R₂ = ?

We know:

[tex]\frac{R_1}{R_2} = \sqrt{\frac{M_2}{M_1} }[/tex]

Substituting the value we get:

[tex]\frac{515}{R_2} = \sqrt{\frac{92}{46} } \\\\\frac{515}{R_2} = \sqrt{2} \\\\R_2 = \frac{515}{\sqrt{2} } \\\\R_2 = 728.32 m/s[/tex]

Therefore, the rate of effusion of gas B is 728.32 m/s