Which activity is an example of chemical change?

same number of each kind of atom appears in the reactants and in the products

Answer:

pH = 4.164

Explanation:

The first process is to find the initial moles for the base (B) & the acid (HA)

i.e.

[tex]= \dfrac{27 mL \times 0.0758 \ moles \ \ of \ B}{1000 \ mL}[/tex]

[tex]=0.0020466[/tex]

[tex]\simeq 2.047\times 10^{-3} \ moles \ of \ B[/tex]

[tex]= \dfrac{27 mL \times 0.0553 \ moles \ \ of \ HA}{1000 \ mL}[/tex]

[tex]=0.0014931[/tex]

[tex]\simeq 1.493\times 10^{-3} \ moles \ of \ HA[/tex]

The acid with base reaction is expressed as;

          HA              +      B         →             A⁻            +         HB⁺

to    1.493 × 10⁻³       2.047 × 10⁻³             -                         -

    -  1.493 × 10⁻³       1.493 × 10⁻³         1.493 × 10⁻³         1.493 × 10⁻³

            0                    5.54 × 10⁻⁴         1.493 × 10⁻³         1.493 × 10⁻³

From observation; both the acid & base weak

Given that:

The pKa for base = 4.594

The pKa for acid = 3.235

Recall that;

pKa = -log Ka

So; Ka = [tex]\mathbf{10^{-Ka}}[/tex]

By applying this:

For Base; Ka = [tex]10^{-4.594}[/tex] = 2.5468 × 10⁻⁵

For Acid:  Ka = [tex]10^{ -3.235}[/tex] = 5.821 × 10⁻⁴

After the reaction; we have the base with its conjugate acid & conjugate base of acid; Thus, since the conjugate acid of the base possesses a higher value of K, it is likely it would be the one to define the pH of the solution.

By analyzing the system, we have:

              HB⁺         + H₂O           ↔           B          +            H₃O⁺

     [tex]\dfrac{1.493\times 10^{-3}}{0.1 \ L}[/tex]                                 [tex]\dfrac{5.54\times 10^{-4}}{0.1 \ L}[/tex]

to   0.01493 M                                 0.00554   M

  -      x                                                   x                                x

    0.01493 - x                                 0.00554 - x                     x

Thus;

[tex]2.5468 \times 10^{-5} = \dfrac{(0.00554 -x)\times x}{(0.01493-x)}[/tex]

Using the common ion effect;

0.00554 - x   [tex]\simeq[/tex]  0.00554   &

0.01493 -  x   [tex]\simeq[/tex]   0.01493

∴

[tex]x = \dfrac{2.5468 \times 10^{-5} \times 0.01493}{0.00554}[/tex]

x =  [H₃O⁺] = 6.8635  × 10⁻⁵

∴

pH = -log(6.8635  × 10⁻⁵)

pH = 4.164

Answer:

A

Explanation:

Took at test on this and my teacher said it was right, hopefully I remembered right, also I answered ur other question like this I think lol

Answer:

760 uM

Explanation:

A biochemist carefully measures the molarity of magnesium ion in 47, mL of cell growth medium to be 97 uM. Unfortunately, a careless graduate student forgets to cover the container of growth medium and a substantial amount of the solvent evaporates. The volume of the cell growth medium falls to 6.0 mL. Calculate the new molarity of magnesium ion in the cell growth medium Be sure your answer has the correct number of significant digits.

The problem here is that the amount of magnesium ion remains the same irrespective of the volume.

Amount of magnesium in the growth medium = molarity x volume

    = 97 x [tex]10^{-6}[/tex] x 47 x [tex]10^{-3}[/tex] = 4.559 x [tex]10^{-6}[/tex]

Then, the volume reduced to 6.0 mL, the new molarity becomes;

molarity = mole/volume

       = 4.559 x [tex]10^{-6}[/tex]/6 x [tex]10^{-3}[/tex] = 7.598333 x [tex]10^{-4}[/tex] M = 759.83333 uM

To the correct number of significant digits = 760 uM

Answer:

b

Explanation:

google lol ur welcome

B: Oceanic crust is thinner and more likely to sink.

Answer:

[tex]U_2=48.3kJ[/tex]

Explanation:

Hello!

In this case, since the fist law of thermodynamics helps us to understand how the change in internal energy is defined in terms of the head added to the system and the work done by the system:

[tex]Q+W=\Delta U[/tex]

In such a way, since 8.3 kJ of heat are absorbed by the system, 3.5 kJ are done by the system and the initial internal energy is 43.5 kJ, the final internal energy turns out:

[tex]U_2=U_1+Q-W\\\\U_2=43.5kJ+8.3kJ+3.5kJ\\\\U_2=48.3kJ[/tex]

Best regards!

Answer:

87.50g(1cm^3/1.1738g)=50.345 cm^3

Explanation:

volume units id in cubic centimeters

Answer:

The correct answer is D. Swan received a formal education, while Edison did not.

Explanation:

I did the Unit Test :)

"Thomas Edison: The Master of Improvement,” is about Thomas Edison. Joseph Swan received a formal education, while Thomas Edison did not. Thus, option D is correct.

Thomas Edison was a known American inventor that invented the incandescent light bulb, the camera, phonograph, etc. He used electricity and worked very hard to invent the lightbulb. He received no formal education and believed in self-improvement.

He was a great inventor and fantastic improver that performed various experiments to invent the greatest inventions. Joseph Swan, on the other hand, was a physicist that developed the incandescent light bulb even before Edison.

He invented dry photographic plates and electric lightbulbs. He received proper formal education and sued Edison for the lightbulb patent infringement. He used carbon paper filaments, unlike Edison's metallic filaments in the bulb.

Therefore, in option D. both the scientists, Joseph Swan and Thomas Edison differed in receiving formal education.

Learn more about Thomas Edison, here:

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Answer:

mass

Explanation:

hope this helps you!!

Explanation:

Fnet = ma

Therefore a = Fnet/m = 2.4N/0.94kg = 2.45m/s².

Answer:

2.6  m/s2

Explanation:

Answer:

How does adding a lone pair affect the position of existing atoms and lone pairs? It decreases the angles between the atoms - the atoms are moving closer because they are being repelled further away from the lone pairs then they are from the other atoms

Explanation:

hope it helps!

Answer:

I'm not going to give you notes but I'm going to give you a tip for notes take what you think is the most important thing about the text and basically paraphrase it into your own words if that helps

Answer:

a. pentane = C5H12

b. Heptane = C7H16

c. Hexyne = C6H10

d. Octene = C8H16

e. Nonane = C9H20

Hope it helps.

1-pentene

Molecular Formula C5H10

Condensed Structural FormulaCH2=CH(CH2)2CH3

Melting Point (°C)–138

Boiling Point (°C)30

2- heptane is the straight-chain alkane with the chemical formula H3C(CH2)5CH3 or C7H16, and is one of the main components of gasoline (petrol).

Answer:

The correct answer is D

Explanation:

Wetlands are environments that are either submerged under water or are frequently wet. Marshes, swamps, bogs, and fens are examples of freshwater wetlands. Here small streams flow into larger streams and wetlands. The correct option is D.

Ecosystems in freshwater wetlands are impacted by transient or ongoing flooding. They are essential habitats for fauna (including migratory species), play a significant role in the regulation of water flow and water quality to entire catchments, and offer shelter for fauna during droughts.

In tropical and subtropical areas, mangrove swamps are coastal wetlands. In brackish to saline tidal waters, they are distinguished by halophytic (salt-loving) trees, shrubs, and other plants.

Thus the correct option is D.

To know more about wetlands, visit;

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Answer:

fluorine

Explanation:

has the highest electronegativity?

Explanation:

Objects with a lower density will float while objects with a higher density will sink.

Since 0.8g/cm³ < 1.0g/cm³,

The log will float in freshwater.

Answer:

75%

Explanation:

on edg :)

Answer:

I will give them advice, that do the power of flame low....

Explanation:

thanks.

Answer:

102.807 kPa

Explanation:

There are some assumptions to be made in the answer. The air inside the balloon acts as an ideal gas at a given temperature conditions.

Using the combined ideal gas equation.

P= absolute pressure of the air inside the balloon.

V= volume of air inside the balloon (6.23 L= 6.23 * 10⁻³ m³)

n= moles of gas(air). (0.250 mol)

R= Universal gas constant ( 8.314 J / mol·K)

T= Temperature in Kelvin

T= 35 + 273.15 = 308.15 K

P= 102.807 * 10³ Pa

P= 102.807 kPa

width=10cm

length=2xwidth=2x10=20cm

height=width/2=10/2=5

V=w*l*h=10*20*5=1000cm^3

Answer:

1000cm^3

Explanation:

first collect what is known

width 10cm

length 2×width (2×10cm) =20cm

height width/2 (10cm/2) =5cm

now if we use the formula for finding volume of a cuboid that has length, width and height known;

V = l×w×h

= 20cm × 10cm × 5cm

= 1000cm^3

Answer:

[tex] \huge 3.986 \times { 10}^{ - 5} \: \: mol \\ [/tex]

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

[tex]n = \frac{N}{L} \\[/tex]

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

[tex]n = \frac{24 \times {10}^{18} }{6.02 \times {10}^{23} } \\ \\ = 3.986 \times { 10}^{ - 5} \: \: mol[/tex]

Hope this helps you

Answer:

75%

Explanation:

3/4 is 75% if you multiply by 25

Answer:

I saw B, he vented SUS

Explanation:

Iodoethane Is the answer.

Answer:

Krypton (Kr)

Explanation:

Nonmetals are the elements that have opposing features and characteristics of metals. Nonmetals do not shine and are dull in appearance. They are bad conductors of heat and electricity. They are brittle and cannot be beaten into sheets. The density, melting and boiling points of the nonmetals are low. Krypton (Kr) is a non metal whose atomic number is 36.

Answer:

Because while our lakes are Great, they're comparatively much smaller than oceans. And the gravitational pull isn't strong.

Answer:

The sign is negative (-)

Explanation:

it shows that heat was give off to the surrounding

Answer:D

Explanation:

Your skin makes vitamin D

Your skin prevents dehydration

And your skin maintains body temperature. So you are left with D

Answer:

The correct option is D.

works with bones to help you move

Explanation:

Skin is the outer layer of the body and it is the body's largest organ.

It protect the body from heat and other harmful substances.

It is comprises of three layers;

The Epidermis which is the outer layer.

The dermis which is a fibrous later that protect the Epidermis.

The subcutis is the subcutaneous layer that is beneath the dermis.

Function of the skin.

1. It's regulate body temperature

2. It's protect the body from heat and pathogenic entry.

3. It produces vitamin D

4. The skin allow sensations or feelings of touch, heat, and cold.

Therefore;

works with bones to help you move is wrong because it is the muscle that work with the bone.

Answer:

Water vapor retains the same heat energy.

Answer:

water vapor gives up heat energy.

Explanation:

Took a quiz and got it right