Why is the atomic theory a theory and not a law?
10 Points)
A theory is the best possible explanation based on all existing evidence.
A theory is a pattern in nature.
O A theory does not change.
O A theory is more important than a law.

Answer:

The half-life varies depending on the isotope.

Half-lives range from fractions of a second to billions of years.

The half-life of a particular isotope is constant.

Explanation:

Make sure you add the options

Answer:c

Explanation: more expensive so people use nonrenewed energy more.

Answer:

The desert should be divided into different types based on its properties. The organisms living in specific type of desert should be named accordingly.

Explanation:

There are usually five major types of desert in the world. Tropical, rainy, semi arid desert, coastal desert and dry desert. There are many different types of organisms living in these deserts. The biodiversity has made it difficult for the humans to analyse and identify the millions of different types. The best way is to organize and name the organisms that live in specific types of deserts.

Answer:

K₂ = 1.12s⁻¹

Explanation:

Based on Arrhenius equation:

ln K₂/K₁ = -Ea/R (1/T₂ - 1/T₁)

Where K is rate constant,

R is gas constant (8.314J/molK),

T is absolute temperature (In K) Of 1, initial state and 2, final state.

ln K₂/K₁ = -Ea/R (1/T₂ - 1/T₁)

ln K₂/2.10x10⁻²s⁻¹ = -82000J/mol/8.314J/molK (1/(273.15 + 58) - 1/(273.15 + 19))

ln K₂ / 2.10x10⁻²s⁻¹ = 3.976

K₂ / 2.10x10⁻²s⁻¹ = 53.3

Answer:

O2

Explanation:

Diatomic molecules are molecules that have 2 of either H,N,F,O,I,Cl, or Br. In this case, 2H is not correct because the 2 is in front of the element name. Diatomic molecules will have the two after which means that the molecule has these two elements together.

Answer: the type of cup

Explanation: the independent variable is what you change in your experiment, to find out the different results, in this experiment the factor that they are changing in order to see which outcome is best, is the type of cup.

The question is incomplete, the complete question is:

This is the chemical formula for cassiterite (tin ore): SnO2 A geochemist has determined by measurements that there are 13. moles of tin in a sample of cassiterite. How many moles of oxygen are in the sample? Round your answer to 2 significant digits.

Answer:

Explanation:

In SnO2, there are two moles of oxygen for each mole of tin.

Hence, if there are 13 moles of tin, then we should have 13 * 2 moles of oxygen. This gives us 26 moles of oxygen.

Hence there are 26 moles of oxygen.

Answer:

ethyl acetate layer

Explanation:

This question tests your knowledge of the principle of solvent extraction.

In solvent extraction, there is always an organic layer and an aqueous layer. The ethyl acetate is the organic layer while the sodium bicarbonate is the aqueous layer.

A brominated aromatic compound will be extracted into the organic layer (ethyl acetate layer).

Answer:

Cell wall, chloroplast, and vacuoles

Explanation:

Answer:

NH₂O

Explanation:

Given compound:

       N₄H₈O₄

Unknown:

The empirical formula of the compound  = ?

Solution:

The empirical formula of a compound is its simplest formula. It expresses the composition of a the compound in the simplest whole ratio of atoms of the different elements present in the compound.

 For the given compound:

                                  N₄H₈O₄

  Number of moles of N = 4

                                      H = 8

                                      O = 4

 the highest common factor is 4 and we simply divide through by this number;

                                      N = 1

                                      H = 2

                                      O = 1

So, the empirical formula of compound is NH₂O

Answer:

See explanation

Explanation:

A drying tube prevents moisture from contaminating the reactants. The drying tube contains CaCl2 a hygroscopic material whose function is to absorb the moisture so that it does not react with the Grignard reagent. Without the desiccating action of CaCl2, moisture will enter the reaction chamber,contaminating the reactants.

If water reacts with the Grignard reagent, an alkane is formed. The mechanism of this reaction is shown in the image attached. R here represents the alkyl moiety of the Grignard reagent.

Answer:

C₃H₆

Explanation:

We'll begin by calculating the empirical formula for cyclopropane. This is illustrated below:

Carbon (C) = 85.7%

Hydrogen (H) = 14.3%

Divide by their molar mass

C = 85.7/12 = 7.14

H = 14.3/1 = 14.3

Divide by the smallest:

C = 7.14/7.14 = 1

H = 14.3/7.14 = 2

Therefore, the empirical formula for the cyclopropane is CH₂

Next, we shall determine the number of mole of cyclopropane.

This can be obtained as follow:

Temperature (T) = 50 °C = 50 °C + 273 = 323 K

Pressure (P) = 0.984 atm

Volume (V) = 1 L

Gas constant (R) = 0.0821 atm.L/Kmol

Number of mole (n) of cyclopropane =.?

PV = nRT

0.984 × 1 = n × 0.0821 × 323

Divide both side by 0.0821 × 323

n = 0.984 / (0.0821 × 323)

n = 0.0371 mole

Next, we shall determine the molar mass of cyclopropane. This can be obtained as follow:

Number of mole of cyclopropane = 0.0371 mole

Mass of cyclopropane = 1.56 g

Molar mass of cyclopropane =.?

Mole = mass /Molar mass

0.0371 = 1.56/Molar mass

Cross multiply

0.0371 × Molar mass = 1.56

Divide both side by 0.0371

Molar mass = 1.56 /0.0371

Molar mass of cyclopropane = 42.05 g/mol.

Finally, we shall determine the molecular formula for cyclopropane. This can be obtained as follow:

[CH₂]ₙ = 42.05

[12 + (2×1)]ₙ = 42.05

[12 + 2]ₙ = 42.05

14n = 42.05

Divide both side by 14

n = 42.05/ 14

n = 3

Thus,

[CH₂]ₙ => [CH₂]₃ => C₃H₆

Therefore, the molecular formula for cyclopropane is C₃H₆

The molecular formula of cyclopropane ([tex]CH_2[/tex]) is equal to [tex]C_3H_6[/tex]

Given the following data:

Scientific data:

To determine the molecular formula of cyclopropane:

First of all, we would determine the molar mass and number of moles of cyclopropane by using the ideal gas law equation;

[tex]PV=\frac{M}{MM} RT[/tex]

Where;

Making MM the subject of formula, we have:

[tex]MM = \frac{MRT}{PV} \\\\MM = \frac{1.56\;\times \;0.0821\times \;323}{0.984\;\times \;1}\\\\MM = \frac{41.3686}{0.984}[/tex]

Molar mass, MM = 42.04 g/mol.

For number of moles:

[tex]Number\;of\;moles = \frac{mass}{molar\;mass}\\\\Number\;of\;moles = \frac{1.56}{42.04}[/tex]

Number of moles = 0.0371 moles

Next, we would determine the empirical formula of cyclopropane:

For carbon (C):

[tex]C = \frac{85.7}{12}[/tex]

Carbon (C) = 7.1417

For hydrogen (H):

[tex]H = \frac{14.3}{1}[/tex]

Hydrogen (H) = 14.3

Simplest whole number ratio:

[tex]C = \frac{7.1417 }{7.1417 } =1[/tex]

[tex]H= \frac{14.3 }{7.1417 } =2[/tex]

Empirical formula of cyclopropane = [tex]CH_2[/tex]

Now, we can determine the molecular formula of cyclopropane:

[tex](CH_2)n = 42.04\\\\(12 + 1\times2)n=42.04\\\\14n=42.04\\\\n=\frac{42.04}{14}[/tex]

n = 3

Molecular formula of cyclopropane ([tex]CH_2[/tex]) = [tex](CH_2)_3 =C_3H_6[/tex]

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Answer:

I want to say option C: four atoms of oxygen. Sorry if I'm wrong

Answer:

Will be more acidic

Explanation:

The equilibrium of NH3 in water is:

NH3(aq) + H2O(l) ⇄ NH4⁺(aq) + OH⁻(aq).

Where equilibrium constant, Kb, is:

Kb = 1.85x10⁻⁵ = [NH4⁺] [OH⁻] / [NH3]

From 0.10M NH3, the reaction will produce X of NH4⁺ and X of OH⁻ and Kb will be:

1.85x10⁻⁵ = [X] [X] / [0.10M]

1.8x10⁻⁶ = X²

X = 1.34x10⁻³ = [OH⁻]

As pOH = -log[OH⁻] = 2.87

And as pH = 14 - pOH

pH of the 0.10M NH3 is 11.13

Now, to find the pH of the NH4Cl and NH3 we need to use H-H equation for bases:

pOH = pKb + log [NH4⁺] / [NH3]

Where pKb is -log Kb = 4.74 and [] are moles of both compounds.

Moles of [NH4⁺] = [NH3] = 60mL, 0.060L*0.22M = 0.0132moles:

pOH = 4.74 + log [0.0132] / [0.0132]

pOH = 4.74

pH = 14 - 4.74 = 9.26

That means the pH of the resulting solution will be more acidic

Answer: B

Explanation: a calcium ion has a charge of +2 because it has 2 more protons than electrons giving it a positive charge instead of neutral or negative.

Answer:

Explanation:

a) O₂(g) + 2H₂(g) = 2H₂O

b) H₂O(l) = H₂O(s)

c) NH₃(g) + HCl(g) =  NH₄Cl(g)

d) 2NH₄NO₃(s) =  2N₂(g) + O₂(g) + 4H₂O(g)

e) N₂O₄(g) =  2NO₂(g)

ΔS is positive when there is increase in disorderliness. It happens when there is increase in volume .

Increase is volume is maximus in the following reaction.

d) 2NH₄NO₃(s) =  2N₂(g) + O₂(g) + 4H₂O(g)

in this reaction solid NH₄NO₃ is changed to 7 x 22.4 L of gases so there is maximum increase in volume . Hence maximum increase in entropy . Hence ΔS is most positive .

Answer:

5 g

Explanation:

From the question, we have,

Molarity of FeIII solution= 0.245 M

Volume of solution = 125 ml

From

number of moles= concentration × volume

We have;

Number of moles= 0.245 M × 125/1000

Number of moles = 0.031 moles

Molar mass of Fe III = 162.5g/moles

Mass of iron III = number of moles× molar mass = 0.031 × 162.5= 5 g

n

Answer:

1) easy compressed

2) fills its container

3) far more space

Explanation:

Answer:

The energy of each transition is approximately [tex]1.98\times 10^{-19}\; \rm J[/tex].

The frequency of photons released in such transitions is approximately [tex]3.00\times 10^{14}\; \rm Hz[/tex].

Explanation:

The Rydberg Equation gives the wavelength (in vacuum) of photons released when the electron of a hydrogen atom transitions from one main energy level to a lower one.

The Rydberg Equation gives the following relation:

[tex]\displaystyle \frac{1}{\lambda_\text{vac}} = R_\text{H} \cdot \left(\frac{1}{{n_2}^2}} -\frac{1}{{n_1}^2}\right)[/tex].

Rearrange to obtain and expression for [tex]\lambda_\text{vac}[/tex]:

[tex]\displaystyle \lambda_\text{vac} = \frac{1}{\displaystyle R_\text{H}\cdot \left(\frac{1}{{n_2}^2} - \frac{1}{{n_1}^2}\right)}[/tex].

In this question, [tex]n_1 = 7[/tex] while [tex]n_2 = 3[/tex]. Therefore:

[tex]\begin{aligned} \lambda_\text{vac} &= \frac{1}{\displaystyle R_\text{H}\cdot \left(\frac{1}{{n_2}^2} - \frac{1}{{n_1}^2}\right)} \\ &\approx \frac{1}{\displaystyle 1.09678 \times 10^{7}\; \rm m^{-1} \cdot \left(\frac{1}{3^2} - \frac{1}{7^2}\right)} \approx 1.0 \times 10^{-6}\; \rm m \end{aligned}[/tex].

Note, that [tex]1.0\times 10^{-6}\; \rm m[/tex] is equivalent to [tex]1000\; \rm nm[/tex]. That is: [tex]1.0\times 10^{-6}\; \rm m = 1000\; \rm nm[/tex].

Look up the speed of light in vacuum: [tex]c \approx 3.00\times 10^{8}\; \rm m \cdot s^{-1}[/tex]. Calculate the frequency of this photon:

[tex]\begin{aligned} f &= \frac{c}{\lambda_\text{vac}} \\ &\approx \frac{3.00\times 10^{8}\; \rm m\cdot s^{-1}}{1.0\times 10^{-6}\; \rm m} \approx 3.00 \times 10^{14}\; \rm Hz\end{aligned}[/tex].

Let [tex]h[/tex] represent Planck constant. The energy of a photon of wavelength [tex]f[/tex] would be [tex]E = h \cdot f[/tex].

Look up the Planck constant: [tex]h \approx 6.62607 \times 10^{-34}\; \rm J \cdot s[/tex]. With a frequency of [tex]3.00\times 10^{14}\; \rm Hz[/tex] ([tex]1\; \rm Hz = 1\; \rm s^{-1}[/tex],) the energy of each photon released in this transition would be:

[tex]\begin{aligned}E &= h \cdot f \\ &\approx 6.62607 \times 10^{-34}\; \rm J\cdot s^{-1} \times 3.00 \times 10^{14}\; \rm s^{-1} \\ &\approx 1.98 \times 10^{-19}\; \rm J\end{aligned}[/tex].

The energy of the transition between n = 7 and n = 3  is 1.96 × 10^-19 J while the frequency is 3 × 10^14 Hz.

Using the Rydberg Equation for energy;

ΔE = -RH(1/n^2final - 1/n^2initial)

Given that;

nfinal = 3

ninitial = 7

RH = 2.18 × 10^-18 J

ΔE = - 2.18 × 10^-18(1/3^2 - 1/7^2)

ΔE = - 2.18 × 10^-18(0.11 - 0.02)

ΔE = - 1.96 × 10^-19 J

For the second part;

Since the wavelength is 1000nm, we have;

λ = 1000nm

c = 3 × 10^8 m/s

f = ?

c = λf

f = c/λ

f = 3 × 10^8 m/s/1000 × 10^-9 m

f = 3 × 10^8 m/s/ 1 × 10^-6 m

f = 3 × 10^14 Hz

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Answer:

Ka = 3.50x10⁻⁴

Explanation:

First, we need to convert the unit of 3.60 g/L to mol/L:

[tex] C_{C_{9}H_{8}O_{4}} = 3.60 \frac{g}{L}*\frac{1 mol}{180.16 g} = 0.0200 mol/L [/tex]

The reaction dissociation of aspirin in water is:

C₉H₈O₄  +  H₂O  ⇄  C₉H₇O₄⁻ + H₃O⁺    

0.02 - x                        x             x

The constant of the above reaction is:

[tex] Ka = \frac{[C_{9}H_{7}O_{4}^{-}][H_{3}O^{+}]}{[C_{9}H_{8}O_{4}]} [/tex]

[tex] Ka = \frac{x^{2}}{0.02 - x} [/tex]

To find Ka we need to find the value of x. We know that pH = 2.6 so:

[tex] pH = -log[H_{3}O^{+}] [/tex]

[tex] 2.6 = -log(x) [/tex]

[tex] x = 2.51 \cdot 10^{-3} M = [H_{3}O^{+}] = [C_{9}H_{7}O_{4}^{-}] [/tex]

Now, the concentration of C₉H₈O₄ is:

[tex] C_{C_{9}H_{8}O_{4}} = 0.02 - 2.51 \cdot 10^{-3} = 0.018 M [/tex]

Finally, Ka is:

[tex] Ka = \frac{[C_{9}H_{7}O_{4}^{-}][H_{3}O^{+}]}{[C_{9}H_{8}O_{4}]} = \frac{(2.51 \cdot 10^{-3})^{2}}{0.018} = 3.50 \cdot 10^{-4} [/tex]

Therefore, the Ka of aspirin is 3.50x10⁻⁴.

I hope it helps you!

Answer:

Explanation:

Al(s) + 3/2 Br₂(l) = AlBr₃(s)

K = [  AlBr₃] / [ Al] [  Br₂]³/²

K² =  [  AlBr₃]² / [  Al ] ² [ Br₂]³

2 AlBr₃ = 2 Al(s) + 3 Br₂(l) =

K₁ =  [  Al ] ² [ Br₂]³ /  [  AlBr₃]²

K₁ =  ( 1 / K² ) = K⁻²

2 ) 2 Al(s) + 3 Br₂(l) = 2 AlBr₃(s)

K₂ = [ AlBr₃ ]² / [  Al ]² [  Br₂ ]³

K₂ = K²

3 )

AlBr₃(s) =   Al(s) + 3/2 Br₂(l)

K₃  = [ Al ] [ Br₂ ] ³/² / [ AlBr₃ ]

=  ( 1 / K ) = K⁻¹

Answer:

The ΔH for the reaction is -456.5 KJ

Explanation:

Here we want to determine ΔH for the reaction;

Mathematically;

ΔH = ΔH(product) - ΔH(reactant)

In the case of the first reaction;

ΔH = ΔH(CaO) + ΔH(CO2) - ΔH(CaCO3)  ...........................(*)

From the other reactions, we can get the respective ΔH for the individual molecule in the reaction

In second reaction;

Kindly note that for elements, molecule of gases, ΔH = 0

What this means is that throughout the solution;

ΔH(Ca)  = 0 KJ

ΔH(O2) = 0 KJ

ΔH(C) = 0 KJ

Thus, in writing the equation for the subsequent chemical reactions, we shall need to write and equate the overall ΔH for the reaction to that of the product alone

So in the second reaction

ΔH = 2ΔH(CaCO3)

Thus;

-2414/2 = ΔH(CaCO3)

ΔH(CaCO3) = -1,207  KJ

Moving to the third reaction, we have;

ΔH = ΔH(CO2)

Hence ΔH(CO2) = -393.5 KJ

For the last reaction;

ΔH = ΔH(CaO)

Hence ΔH(CaO) = -1270 KJ

Going back to equation *

ΔH = ΔH(CaO) + ΔH(CO2) - ΔH(CaCO3)

Using the values of the ΔH  of the respective molecules given above,

ΔH  = -1270 + (-393.5) - (-1207)

ΔH  = -456.5 KJ

Answer:

Explanation:

Significant figure implies number of digits that are to be considered. Some rules are required to be considered when writing a given expression to an expected significant figures.

So that:

1) 0.00004050 is 4 significant figures

2) 54.7000 is 6 significant figures

3) 1,000.09 is 6 significant figures

4) 0.039 is 2 significant figures

Answer:

The wavelength of light (in nm) of the spectral line of Hydrogen where an electron falls from the 6th Bohr orbit to the 3rd Bohr orbit is 1090nm

Explanation:

We know that , the wavelength of the light is calculated by Rydberg's formula-

[tex]\frac{1}{\pi} =R^2(\frac{1}{n^2_1} -\frac{1}{n^2_2})[/tex]  [tex][n_2>n_1][/tex]

Here , R = Rydberg's constant [tex](1.097\times 10^7 m^-^1)[/tex]

          Z = atomic number (for hydrogen , Z= 1)

     [tex]n_2 =6 , n_1=3[/tex]

[tex]\pi =[/tex] wavelength of light

Now , putting the values in the Rydberg's formula ,

  [tex]\frac{1}{\pi} =1.097\times10^7m^-^1(\frac{1}{3^2} -\frac{1}{6^2} )[/tex]

     =[tex]1.097\times 10^7m^-^1 (\frac{4-1}{36} )[/tex]

    =[tex]1.097\times 10^7m^-^1(\frac{3}{36} )[/tex]

      =[tex]1.097\times 10^7m^-^1(\frac{1}{12} )[/tex]

  [tex]\frac{1}{\pi}[/tex]   = [tex]0.0914167\times 10^7m^-^1[/tex]

[tex]\pi=\frac{1}{0.0914167\times10^7m^-^1}[/tex]

[tex]\pi=10.9389\times10^-^7\\\pi=1093.89\times10^-^9m[/tex]

  =1090nm

Hence , the wavelength of the light is 1090nm,, that is option D is correct.

Answer:

Endothermic reaction

Explanation:

Endothermic reactions are defined as the type of chemical reaction in which the system absorbs the energy from the surroundings and the temperature of the surrounding decreases while in Exothermic reactions, heat is released by the system to the surroundings and it makes the surrounding warm.

The given example is an "endothermic reaction" because the reaction between NH4Cl and water is making the surrounding cool (cold pack) due to the release of heat.

Hence, the correct answer is "endothermic reaction".

Answer:

30 neutrons

Explanation:

Since the mass of the iron nuclide is 56 , there must be 56−26=30 neutrons, 30 massive, neutral particles in this iron nucleus.

Answer:

The mass of N a H C O 3 present is 2.431 g

Explanation:

The sample contains 57.2 % N a H C O 3  by mass.

To find the mass of N a H C O 3  in the sample, we need to find what the equivalent of 57.2 %.

Mass of N a H C O 3  = Percentage Composition * Mass of sample

Mass of N a H C O 3  = 57.2 / 100     * 4.25

Mass of N a H C O 3   = 2.431 g

The mass of N a H C O 3 present is 2.431 g

The mass of the compound (NaHCO₃) contained in 4.25 g is 2.431 g.

The given parameters;

The mass of the compound (NaHCO₃) contained in 4.25 g is calculated by the finding its equivalent in the given percent composition as follows;

[tex]mass \ = \frac{57.2}{100} \times 4.25\\\\mass = 2.431 \ g[/tex]

Thus, the mass of the compound (NaHCO₃) contained in 4.25 g is 2.431 g.

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Answer:

[H+] = 7.576x10⁻⁴M

pH = 3.12

Explanation:

Based on the equilibrium of the nicotinic acid in water:

HC6H4NO2(aq) + H2O(l) ⇄ C6H4NO2-(aq) + H3O+(aq)

Ka = [C6H4NO2-] [H3O+] / [HC6H4NO2]

As both C6H4NO2-(aq) and H3O+(aq) comes from the same equilibrium, we can approximate their concentration as X and replace:

Ka = [C6H4NO2-] [H3O+] / [HC6H4NO2]

1.4x10⁻⁵ = [X] [X] / [0.041M]

5.47x10⁻⁷ = X²

And as pH is defined as -log [H⁺]