Select two that are true

When One mole of hydrogen is burned in oxygen to produce water in the gas phase, 285.8 kJ of heat is released.Hence, option (D) is correct

An enthalpy change is approximately equal to the difference between the energy used to break bonds in a chemical reaction and the energy gained by the formation of new chemical bonds in the reaction.

It describes the energy change of a system at constant pressure. Enthalpy change is denoted by ΔH.

The energy change that occurs when one mole of a compound is burnt in excess oxygen under standard bis called the standard enthalpy change of combustion.

Hence, When One mole of hydrogen is burned in oxygen to produce water in the gas phase, 285.8 kJ of heat is released.Thus, option (D) is correct

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The work function is 4.74eV if light frequency [tex]1.40 X 10^{15}[/tex] Hz strike a surface causing photoelectrons to leave with a KE of 1.05 eV.

When light whose frequency is more than the threshold frequency incident on the metal, electrons are emitted. Such electrons are called photoelectrons.

The photoelectric effect is a phenomenon in which a beam of light is projected towards a metal plate and this leads to the ejection of electrons from the metal. The minimum amount of energy required for this ejection of electrons is known as the work function. When the energy of the light beam is less than the work function, then the electrons are not emitted.

The photoelectric effect is represented by the equation:

E = φ + KE  where

E = energy of the incident photons

KE = kinetic energy of photoelectrons

φ = Work function of the metal

This can also be written in terms of frequency as:

h = h₀ +  [tex]\frac{1}{2}[/tex]mv²

h₀= frequency of the incident light beam

m = mass of the electron

v = velocity of the electron

h = Plank's constant 6.623 x 10⁻³⁴Js

Conversion factor: 1eV = 1.602 x 10⁻¹⁹ J

So, 1.05eV = 1.682 10⁻¹⁹ J

Using the formulas,

(6.623 x 10⁻³⁴Js)(1.40x10¹⁵ s⁻¹) = φ + 1.682 x 10⁻¹⁹ J

(9.272 x 10⁻¹⁹) - (1.682 x 10⁻¹⁹) = φ

φ = 7.590 x 10⁻¹⁹ J = 4.74 eV

Hence, the work function is 4.74eV if light frequency 1.40x10^15 Hz strike a surface causing photoelectrons to leave with a KE of 1.05 eV.

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There are three sigma bonds, so hybridization of the molecule will be sp²

Answer: A

Explanation:

Oxidation is the process through which electrons are gained. This indicates that only organisms on the electron side have the potential to be oxidizing agents. c, d, and e are, by definition, eliminated.

We also know that H+ is in the +1 oxidation state. The same is true for 'H' in H2O... it doesn't change oxidation states

Therefore, the answer must be a) nitrate

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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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

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

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: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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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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The FORMULA for the limiting reagent is [tex]ZnOH_2[/tex].

4.27 grams of reactant remains after the reaction is complete.

The limiting reagent is the reactant that is completely used up in a reaction and thus determines when the reaction stops.

Given data:

Mass of sulfuric acid = 41.0 grams

Molar mass of sulfuric acid = 98.08 g/mol

Mass of zinc hydroxide = 36.5 grams

Molar mass of zinc hydroxide = 99.424 g/mol

Step 1:moles sulfuric acid = mass sulfuric acid / molar mass sulfuric acid

moles sulfuric acid = 41.0 grams / 98.08 g/mol

moles sulfuric acid = 0.41 moles

Step 2: moles of zinc hydroxide

moles zinc hydroxide = 36.5 grams / 99.424 g/mol

moles zinc hydroxide =0.367 moles

Step 3: Calculate limiting reactant

zinc hydroxide is the limiting reactant. It will completely be consumed.

There will remain 0.41 moles - 0.367 moles = 0.043 moles

This is 0.043 moles x 99.424 g/mol

= 4.27 grams

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Answer:

1. Thermometer– It is used to measure air temperature.

2. From time to time– In 2–4hrs after sunrise, the air temperature rises the fastest. Around 1hr before sun set, the air temperature drops the fastest. The solar radiation reaches its highest value at noon.

3. Anemometer– it is used to measure wind speed and direction.

4. Direction– The wind vane originally measures the direction of the wind, but, some modern ones have wind cups attached to them, to measure the wind speed.

5. Anemometer– It is a device that measures wind speed and direction. These, days, some modern wind vanes also measure wind speed.

Explanation:

I hope this helps.

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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Answer:

i believe its called A. periods

V=n/M

V=(6.34:125.55 g/mol)/0.72

V=0.07 L = 70 ml

Rice would not show any negative test with Benedicts solution but will show  blue black color with iodine.

The Benedicts solution is used to test for the presence of reducing sugars in a solution. The brick red color is a positive test for reducing sugars such as glucose.

Owing to the fact that grape does not have starch, it shows a negative test for starch. Rice would not show any negative test with Benedicts solution but will show  blue black color with iodine.

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Explanation:

it applies to pressure laws

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:

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 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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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:

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﹏⊂)

16 cells are produced from a single parent cell after the fourth division of the cell.

In biology, the smallest unit can live on its own and that makes up all living organisms and the tissues of the body.

In mitosis type of cell division, one parent cell is divided into two same or different daughter cells. In this way, in the first division, two cells are produced from single parent cells and in the second division, four daughter cells are produced. In the third division, 8 cells are produced from 4 parent cells and in the fourth division, 16 cells are formed from 8 cells.

So we can conclude that 16 cells are produced from a single parent cell after the fourth division of the cell.

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Answer:

C

Explanation:

Marble is the correct answer

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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Answer: .75 M

Explanation:

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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