what kind of investigations allow for the control of variables?

Question 1

1) The formula of iron(II) iodide is [tex]\text{FeI}_{2}[/tex] and has a formula mass of 309.654 g/mol. This means that in 12.2 grams, there are

So, the molarity is (0.039398812868557)/(0.5) = 0.0788 M (to 3 sf)

2) In 0.039398812868557 mol of iron(II) iodide, there are 0.039398812868557 moles of iron(II) iodide cations, and thus the molarity is still 0.0788 M (to 3 sf)

3) In 0.039398812868557 mol of iron(II) iodide, there are

Thus, the molarity is (0.078797625737114)/(0.5) = 0.158 M (to 3 sf)

Question 2

1) The formula of iron(III) sulfate is [tex]\text{Fe}_{2}\text{(SO}_{4})_{3}[/tex] and has a formula mass of 399.9 g/mol. This means that in 16.8 grams, there are

So, the molarity is (0.042010502625656)/(0.25) = 0.168 M (to 3 sf)

2) In 0.042010502625656 moles of iron(III) sulfate, there are 2(0.042010502625656)=0.084021005251312 moles of iron(III) cations, so the molarity is:

3) In 0.042010502625656 moles of iron(III) sulfate, there are 3(0.042010502625656)=0.12603150787697 moles of sulfate anions, so the molarity is:

Question 3

Since we need 50.0 mL of solution at 0.271 M,

So, we need this from 12.0 M HBr so, meaning that:

The following is an insoluble compound that is likely to be produced by the reaction below CaSO4 + PbI- CaI + PbSO4. The PbSO4 will be insoluble as The sulfates are insoluble in water besides for the sulfates of calcium, barium, mercury, and lead.

Lead sulphate ($PbS$) is insoluble in water due to the fact water's dipole electricity is simply too vulnerable to shy away the ions (each anion and cations) from the sturdy crystals of lead sulphate.Lead sulfate seems as a white crystalline solid. Insoluble in water and sinks in water. Contact might also additionally aggravate skin, eyes, and mucous membrane.

Thus, PbSO4 is insoluble. In PbSO4 , the electricity of the dipole is vulnerable to interrupting the anionic and cationic bond. So, PbSO4 stays insoluble in solution.

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The pH of a 0.64 M solution of pyridine (C₅H₅N) is 9.52.  

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.

The equation for the protonation of the base pyridine is the following:

C₅H₅N + H₂O ⇄ C₅H₅NH⁺ + OH⁻   (1)

Kb = 1.7 × 10⁻⁹ (Given)

To calculate the pH of the solution we need to use the following equation:

pH + pOH = 14

pH = 14 - pOH

     =14 - [-log[OH⁻]]

    = 14 + log[OH⁻]

Now, we need to find the concentration of the OH⁻ ions. Since pyridine is a weak base, at the equilibrium we have (eq 1):

C₅H₅N  +  H₂O  ⇄  C₅H₅NH⁺  +  OH⁻

0.64 - x                          x              x

After entering the values of [C₅H₅N] = 0.64-x, [C₅H₅NH⁺] = x, and [OH⁻] = x, into equation (2) we can find the concentration of OH⁻:

1.7 × 10⁻⁹  =[C₅H₅NH⁺]  [OH⁻]  /  [C₅H₅N]

                = x . x / 0.64-x

1.7 × 10⁻⁹ (0.64-x) - x² = 0

Solving the above quadratic equation for x, we have :

Now, We can calculate the pH, after taking the positive value, x₂, (concentrations cannot be negative) and entering into above equation :

pH = 14 + log[OH⁻]

     = 14 + log (3.32 x 10⁻⁵)

     = 9.52

Therefore, the pH of the solution of pyridine is 9.52.

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Explanation:

it applies to pressure laws

Answer:31,631.04

Explanation: multiply final temp with initial temp = 42 then multiplied by grams = 7,560 then multiplied by J = 31,631.04

If the balloon had a volume of 3 L at a depth of 50 m, the original volume of the balloon will be

Significant figures are the number of digits in a value, often a measurement, that contribute to the degree of accuracy of the value.

The pressure at a depth of 40 m is the hydrostatic pressure of the water plus the atmospheric pressure.

The hydrostatic pressure P of a liquid is given by the formula ;

P = ρgh

where,

P =  1000 kg m⁻³ x 9.81 ms⁻² x 50 m

   = 1000 kg m⁻¹ x 9.81 s⁻² x 50

   = 4.9 x 10⁵ Pa

Lets's Convert Pa in to atm

    =   4.9 x 10⁵ Pa x 1 / 103. 325 x 10³ Pa

    = 4.7 atm

Mow, lets calculate P(atm) ;

P(atm) = 14.7 psi x 1 atm / 14.7 psi

          = 1 atm

Total Pressure at 50 m is ;

P(total) = 4.7 atm + 1 atm

            = 5.7 atm

Now we can apply Boyle's Law to calculate the volume of the balloon at the surface.

P₁V₁ = P₂V₂

V₂ = P₁V₁ / P₂

According to the question ;

V₂ = 3 L x 5.7 atm  / 1 atm

     = 17.1 L

     = 20 L ( 1 significant figure)

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Answer:

6.022 x 10²³

Explanation:

The number of atoms =  the number of moles x with the Avogadro's number.

(The Avogadro's number is 6.022 x 10²³ atoms / moles)

number of atoms = 1.00 moles x 6.022 x 10²³ atoms / mole

number of atoms =  6.022 x 10²³ atoms

(There is no need to simplify?) = 6.022 x 10²³

(ps. This is my first time doing this question so im sorry if i got it wrong

(つ﹏⊂)

1.199 M is the concentration of KCI in the resulting solution.

A mole is defined as 6.02214076 × [tex]10^{23}[/tex] 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.

No.of moles of KCI

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

[tex]Moles = \frac{44.7 g}{74.5513 g/mol}[/tex]

= 0.599 moles

Vol.of the solution,V= 500 ml

= 0.5 liter

Molarity

[tex]Molality = \frac{Moles \;solute}{Volume \;of \;solution \;in \;litre}[/tex]

[tex]Molality = \frac{0.599 moles}{0.5 liter}[/tex]

= 1.199 M

Hence, 1.199 M is the concentration of KCI in the resulting solution.

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The molar mass of the unknown gas is determined as 17.75 g.

The rate of gas diffusion is given by Graham's law.

R₁√M₁ = R₂√M₂

where;

[tex]\frac{R_1}{R_2} = \sqrt{\frac{M_2}{M_1} } \\\\\frac{2R_2}{R_2} = \sqrt{\frac{71}{M_1} }\\\\2 = \sqrt{\frac{71}{M_1} }\\\\2^2 = \frac{71}{M_1} \\\\M_1 = \frac{71}{4} \\\\M_1 = 17.75 \ g[/tex]

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The average wavelength of the fluorine molecule will be 2.36 × 10⁻¹¹ metres.

Fluorine Molecule's Speed = 442.4 m/s

The Molar Mass of the F₂ = 38 g/mol

Now as we know that any molecule's

1 mole contain  = 6.022 × 10²³ Molecule

So, 1 Fluorine molecule mass =

Fluorine's Molar mass / Number of Fluorine molecule in 1 mole

So, 1 Fluorine molecule mass = 38 / ( 6.022 × 10²³ )

1 Fluorine molecule mass = 6.31 × 10⁻²³ g

1 Fluorine molecule mass = 6.31 × 10⁻²⁶  Kg

So molecule's momentum = Molecule's mass × Molecule's Velocity

So molecule's momentum = ( 6.31 × 10⁻²⁶ ) × 442.4

So molecule's momentum = 2.8 × 10⁻²³  Kg.m/s

Now wavelength of Fluorine molecule = λ = planks constant / momentum

wavelength of Fluorine molecule = λ = ( 6.626 × 10⁻³⁴ ) / ( 2.8 × 10⁻²³ )

wavelength of Fluorine molecule = λ = 2.36 × 10⁻¹¹ metre

So the wavelength of the diatomic fluorine molecule came out to be 2.36 × 10⁻¹¹ metres after applying all the concepts and formulas.

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The empirical formula would be  [tex]C_2H_3O_2[/tex] and the molecular formula would be  [tex]C_4 H_6 O_4[/tex]

From the illustration:

C = 40.6 g                   H = 5.1 g                      O = 54.2 g

Divide each element by its molar weight:

C = 40.6/12 = 3.4                    H = 5.1/1 = 5.1                  O = 54.2/16 = 3.4

Divide by the smallest:

C = 3.4/3.4 = 1                        H = 5.1/3.4 = 1.5                 O = 3.4/3.4 = 1

Thus, the empirical formula is [tex]C_2H_3O_2[/tex]

To find the molecular formula:

[ [tex]C_2H_3O_2[/tex]]n = molecular formula

where n = molar mass/empirical formula mass

Empirical formula mass = 24 + 3 + 32 = 59

n = 118.084/59 = 2

Thus, the molecular formula is [tex]C_4 H_6 O_4[/tex] which is more or less the same as the empirical formula.

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The Empirical formula will be C₂H₃O₂  and the Molecular formula would be  C₄H₆O₄

Empirical formula is a formula giving the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms.

Molecular formula is a chemical formula that gives the total number of atoms of each element in each molecule of a substance.

Given ;

Divide each element by its molar weight:

Divide by the smallest Value:

Thus, the Empirical formula is C₂H₃O₂

Now, to find the molecular formula ;

[C₂H₃O₂ ]n = molecular formula

where n = molar mass / empirical formula mass

Empirical formula mass = 24 + 3 + 32 = 59

n = 118.084 / 59 = 2

[C₂H₃O₂ ]n = molecular formula

[C₂H₃O₂ ]2 = C₄H₆O₄

Thus, the Molecular formula is C₂H₃O₂

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A voltaic cell is used to produce electrical energy with the help of chemical reactions.

Relating to, or producing direct electric current by chemical action.

A Voltaic Cell (also known as a Galvanic Cell) is an electrochemical cell that uses spontaneous redox reactions to generate electricity. It consists of two separate half-cells.

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Answer:

i believe its called A. periods

In an endothermic reaction, Keq increases as the temperature increases and vice versa.

In an exothermic reaction, Keq decreases as the temperature increases and vice versa.

Therefore, the temperature is the only factor that affects the equilibrium constant of a reaction.

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Answer:

0.004136 moles

Explanation:

From our question we have been asked to determine the quantity in moles of silver atoms having 2.49 × 10²¹ atoms of silver.

We know that from Avogadro's constant, one mole of silver contains 6.02 x 10²³ atoms.

Thus,

1 mole of silver contains 6.02 x 10²³ atoms.

x moles of silver contains 2.49 × 10²¹ atoms

Cross multiply to obtain the number of moles of silver,

x moles = (2.49 × 10²¹ x 1)/(6.02 x 10²³)

= 0.004136 moles

Therefore the quantity of silver in moles is 0.004136 moles

The Sun is presently at a low level of sunspot activity. Hence, option C is correct.

Solar radiation is often called the solar resource for the electromagnetic radiation emitted by the sun.

The Sun is presently at a low level of sunspot activity is the correct answer.

Hence, option C is correct.

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Answer:245.088

Explanation: you subtract final temperature with initial temperature = 46 then multiply by grams = 552 then multiplied by J = 245.088

0.3 L is the final volume when M₁ = 3 M, V₁ = 0.125L, M₂ = 1.25M.

The amount of space occupied by a three-dimensional figure as measured in cubic units.

Given data:

M₁ = 3 M

V₁ = 0.125L

M₂ = 1.25M

V₂ = ?

Solution:

M₁V₁ = M₂V₂

3 M × 0.125L = 1.25M × V₂

V₂ = 0.3 L

Hence, 0.3 L is the final volume.

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Answer:

The new weight-loss supplement was less effective on females in the study. That is because only 65% of them lost weight after two weeks, whereas 74% of the males lost weight after two weeks.

Explanation:

37 out of 50 males lost weight after two weeks, so 74% of males lost weight ( (37 · 2)/(50 · 2) ). 13 out of 20 females lost weight after two weeks, so 65% of females lost weight ( (13 · 5)/(20 · 5) ). This means the supplement was less effective on females because males had a higher percentage of losing weight.

Hope this helps !! :D

Answer:

B. An astronaut in a spaceship

Isolated system :-

In an isolated system, there is no transfer of energy or matter between the system and the environment.

Hope it helps!

Answer: .75 M

Explanation:

The standard enthalpy change associated with the given reaction at 25 °C using the following enthalpies of formation will be − 902.4 kJ

The standard enthalpy change of formation of a compound is the enthalpy change which occurs when one mole of the compound is formed from its elements under standard conditions, and with everything in its standard state.

According to the balanced chemical equation ;

CH₄(g) + 2O₂(g) ⟶ CO₂(g) + 2H₂O(l)

Now,

ΔH⁰ = ΔH⁰f(products) − ΔH⁰f(reactants)

​

       = [ΔH⁰(CO₂) +ΔH⁰(H₂O)] − [ΔH⁰(CH₄) + 2ΔH⁰(O₂)]

       = [−393.5 + 2 x (−285.8)] − [−62.7 + 2 x 0]

        = − 902.4 kJ

Hence, The standard enthalpy change associated with the given reaction at 25 °C using the following enthalpies of formation will be − 902.4 kJ

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Answer:

1,135 grams P₄O₁₀

Explanation:

To find the mass, you need to (1) convert molecules to moles (via Avogadro's Number) and then (2) convert moles to grams (via molar mass from periodic table values). It is important to arrange the ratios/ conversions in a way that allows for the cancellation of units (the desired unit should be in the numerator). The final answer should have 4 sig figs to reflect the given value (2.408 x 10²⁴).

Avogadro's Number:

1 mole = 6.022 x 10²³ molecules

tetraphosphorus decaoxide = P₄O₁₀

Molar Mass (P₄O₁₀): 4(30.974 g/mol) + 10(15.998 g/mol)

Molar Mass (P₄O₁₀): 283.876 g/mol

2.408 x 10²⁴ molecules P₄O₁₀                     1 mole                         283.876 g
-------------------------------------------  x  ------------------------------------  x  -----------------
                                                         6.022 x 10²³ molecules           1 mole

=  1,135 grams P₄O₁₀

Due to the presence of three unpaired electrons, phosphorus is paramagnetic.

Electronic configuration of Phosphorus:-

[Ne] 3S2  3P3

By looking at a substance's electron configuration, one can identify whether or not it has magnetic qualities. If a substance has unpaired electrons, it is paramagnetic; if all of its electrons are paired, it is diamagnetic.

A tiny, positive susceptibility to magnetic fields exists in materials. When exposed to a magnetic field, these materials are only weakly drawn to it; once the external field is removed, they lose their magnetic qualities.

A weak, negative sensitivity to magnetic fields exists in materials. When exposed to a magnetic field, diamagnetic materials are partially repulsed and lose their magnetic properties when the external field is removed.

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The exact mass of one Na - atom is 22.98977 amu and thus, the weight of two sodium atoms in present in Na₂C₆H₆O₇ is 45.979539 g/mol.

The molar mass of a substance is the mass in grams of 1 mole of the substance.

We can obtain a substance's molar mass by summing the molar masses of its component atoms.

Mass of one Na atom = 22.98977

Mass of two Na atom = 22.98977 x 2

                                      = 45.97954

                                       = 45.9 (up to 3 Significant figures)

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Answer:

A

Explanation:

Answer:

The answer is C

To ensure data traceability and accessibility is to complete a study beginning-to-end on a closed system or platform.

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