Which of the following examples is a sign
that a chemical change is occurring?
A. the substance seems to have disappeared
B. the state of the matter has changed
C. the production of heat, light, and smoke

Answer:

             The monomers of polyesters are,

                                  (i) A Dicarboxylic Acid

                                  (ii) A Dialcohol

Explanation:

                     As depicted from name polyester is a macromolecule which contains numerous ester functional groups. Ester is formed by the condensation of Carboxylic acid and alcohol as shown,

                            R-COOH  +  R'OH  →  RCOOR'  +  H₂O

Therefore, in order to utilize this reaction for the formation of long chain of polyesters then one can use a dicarboxylic compounds and dialcohol compounds. This will allow to propagate the chain length depending upon the requirement. Hence, the general reaction for the formation of polyester is shown below. The circle and rectangle specifies different moieties which imparts different characters to the polyester.

Final answer:

The monomer unit of Polyester is made from a reaction between a dicarboxylic acid and a dihydric alcohol, forming ester bonds and water. Polyethylene terephthalate (PET) is a common type of polyester formed from terephthalic acid and ethylene glycol. Polymers have diverse properties and uses based on their composition.

Explanation:

The monomer unit of Polyester typically consists of a dicarboxylic acid combined with a dihydric alcohol, which during a condensation polymerization process, reacts to form an ester bond and water as a byproduct. The chemical formula of this reaction involves two major functional groups: -COOH (carboxylic acid) and -OH (alcohol). In the case of Polyethylene terephthalate (PET), which is the most common polyester, terephthalic acid and ethylene glycol are the monomers that condense to form the repeating units of the polymer.

Polyester is synthesized through a condensation reaction, also known as dehydration synthesis, where each ester linkage formed results in the production of a molecule of water. This is different from hydrolysis reactions, which break down polymers into monomers using water.

Properties and Uses of Polymers:

Explanation:

I think for changing Co 2. to liquid is cooling and high pressure condition .

I hope it's useful.

Under specific conditions of high pressure and low temperature, carbon dioxide gas can turn into a liquid. This requires exceeding the carbon dioxide's triple point, which is 5.1 atmospheres of pressure and -56.6 degrees Celsius.

To turn carbon dioxide gas into liquid form, you would need to create specific conditions of high pressure and low temperature.

Under normal atmospheric pressure, carbon dioxide will sublimate (change directly from a solid to a gas), skipping the liquid phase as it is cooled. However, if the carbon dioxide is subjected to a pressure greater than 5.1 atmospheres at a temperature below -56.6 degrees Celsius, it will turn into a liquid rather than a solid. This is known as the triple point of a substance, the specific set of conditions where a substance can exist in all three states - solids, liquids and gases.

So, basically to make carbon dioxide form a liquid, you would need to increase the pressure and decrease the temperature to a point above its triple point.

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Explanation:

This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary. The other process proposed to contribute to the formation of new oceanic crust at mid-ocean ridges is the "mantle conveyor".

Mid-ocean ridges and ocean trenches has been result in the cycling of matter with the movement of tectonic plates.

Cycling of matter has been defined as the transfer of matter from one place to another. The transfer of matter has been achieved within the ecosystem.

The mid-ocean ridges have been present in the part of the divergent plate boundaries. The ocean trenches have been the convergence of the tectonic plates.

The convergence and divergence of the tectonic plates results in the transfer of matter from one place to another. Thus, mid-ocean ridges and ocean trenches has been result in the cycling of matter with the movement of tectonic plates.

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Answer:

C a chemical reaction formed

Explanation:

if something changes smell and nothing else it is a chemical reaction, every other answer does not make sense

Answer:

chemical reaction

Explanation:

nothing changed with the appearance of how it looks

Answer:

Percent yield = 63.3%

Explanation:

Given data:

Mass of copper = 32.89 g

Mass of oxygen = 32.89 g

Mass of copper(II) oxide formed = 26.20 g

Mass of calcium chloride produced = ?

Solution:

The actual yield of reaction is the amount that you have recovered such as 26.20 g.

Theoretical yield will be calculated in the following way,

Chemical equation:

2Cu + O₂  →  2CuO

Number of moles of Cu:

Number of moles  = Mass /molar mass

Number of moles = 32.89 g / 63.55 g/mol

Number of moles = 0.52 mol

Number of moles of  O₂:

Number of moles = Mass /molar mass

Number of moles  = 32.89 g / 32 g/mol

Number of moles = 1.03 mol

Now we will compare the moles of CuO with Cu and O₂.

                  O₂           :               CuO

                  1               :               2

                 1.03           :            2.06

                Cu              :                CuO  

                 2                :                 2

                  0.52           :             0.52

The number of moles of CuO produced by Cu are less so it will limiting reactant.

Mass of CuO: (THEORETICAL YIELD)

Mass = number of moles × molar mass

Mass = 0.52 mol × 79.55 g/mol

Mass = 41.4 g

Percent yield:

Percent yield = actual yield /  theoretical yield  × 100

Percent yield = 26.20 g/ 41.4 g × 100

Percent yield = 63.3%

When a liquid is cooled, the kinetic energy of the particles decrease and the space between the particles also decrease, and the matter changes its state to solid.

Liquid is the state of matter which is one of the fluid, and its denser than gases but rarer than solids. The particles of liquid have a particular amount of kinetic energy which depends on the temperature of the liquid. As the temperature is decreased, the energy content of the matter as a whole decreases. This in turn, decrease the energy levels of individual molecules, and the kinetic energy of the molecule also decrease.

As the kinetic energy of the molecules decrease, the collision between the molecules decrease. This brings the molecules closer, binding them into the van der Waal's force. Thus they condense into solids.

Answer: option B. Poles

Explanation:

Answer:

B. Poles

Explanation:

The two observation made them came to the conclusion that earth's outer core is liquid is, 'Shear waves' one of energy waves do not travel through the outer layer and the magnetic field found in earth's surface

Explanation:

Answer:

The seed of the blackberry will be released in the faeces of the organisms. The seed of the blackberries will be distributed to different locations. When the seed will be dropped to a favourable location, the seed will germinate and a plant will grow from it. In this way, seeds are able to be dispersed at more favourable locations via animal sources. Hence, they will have better chances of growing in different areas.

Answer: The seeds will be deposited in the animal's waste so that they can grow into a new blackberry plant

Explanation:

Explanation:

Sodium has lower electronegativity value and a largest atom as compared to given element whereas beryllium has least metallic character.

The element Sodium (Na) has a low electronegativity as compared to other given elements. The electronegativity values of sodium is 0.93, beryllium has 1.57, magnesium has 1.31 and lithium has 0.98 so we can say that sodium has lower electronegativity value.

The element Beryllium (Be) has the least metallic character because beryllium is present at the top of the periodic table. When we go from top to bottom metallic character increases and decreases from left to right in the periodic table.

The element Sodium (Na) has the largest atom among these elements because of more number of shells added when we go from top to bottom which make higher the radius of sodium as well as size so we can conclude that sodium has lower electronegativity value and a largest atom as compared to given element whereas beryllium has least metallic character.

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Answer: a. 2K + I2 => 2 KI

Explanation: Potassium or K is in group 1 so its oxidation is 1+ while Iodine is in group 7 so its oxidation is -1. Iodine is expressed as I2 when written individually. So the reaction is K reacts with I2 to produce KI. Then balance the equation by adding 2 to K and 2 to KI to balance the equation.

Answer: tans - 2-pantene

Explanation:

Answer:

Components of air, like carbon dioxide, can be considered pollutants when human activity causes their concentration to be larger than normal. At higher concentrations, naturally occurring gases can have undesirable consequences on the environment. High levels of carbon dioxide can cause an increase in Earth’s temperature.

The naturally occurring components of the air become when the level of any component rises above the normal level. Therefore, carbon dioxide can be a pollutant if its concentration rises too much.

Air pollutants can be described as substances in the air that could present at high concentrations, and harm human beings, vegetation, animals, or material.

Air pollutants include types of matter of any natural or artificial components capable of being airborne. Air pollution can be any physical, chemical, or biological change in the air. Air pollution can be described as the contamination of air by harmful gases, smoke, and dust.

In the atmosphere of the earth, there is a certain percentage or range of gases. Any increase or decrease in the concentration of these gases can be harmful to survival. This imbalance in the gases can result in an increase in the earth’s temperature known as global warming.

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Answer:D physical chemistry

Explanation:when a matter undergo changes i.e transit from one form to another is a study that falls under physical chemistry,basically those changes can be seen,for example water at temperature below 0^°c is seen as ice,a solid structure completely different in structure, characteristics from water while at 100^°c ,it forms vapor a gas .this process involves latent heat and heat capacity and can be actually calculated to understand the mechanism involved.

The liquids will arrange themselves in the order; purple, green, red, blue.

Density is defined as the mass per unit volume of a substance. Usually, in a mixture of liquids, the liquid with lower density is found at the top while liquids with higher densities are found below.

In this problem, we know the following;

Density of red liquid -  1.2 grams per centimeter cubed

Density of blue liquid -  1.6 grams per centimeter cubed

Density of green liquid - 0.8 grams per centimeter cubed

Density of purple liquid- 0.1 grams per centimeter cubed

The liquids will therefore arrange themselves in the order; purple, green, red, blue.

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Answer:

C.

Explanation:

Color

Colour is a physical property that requires no tools, scales, or other equipment to determine. So the correct option is C.

It is the aspect of any object that is described by hue, lightness, and saturation. In physical terms, colour is specifically associated with electromagnetic radiation that is of a certain range of wavelengths. This range of wavelengths is visible to the human eye. The radiation of such wavelengths makes up that part of the electromagnetic spectrum that is known as the visible spectrum or light.

In the perception of colour, vision is involved. A person can see even in dim light, however, in that case, a person is not able to differentiate between colours. When more light is present, colours start to appear clearly. Sometimes, the light of a particular critical intensity is also necessary for the perception of colour.

Lastly, the way the response of the brain to the present visual stimuli is also considered. The same object may appear pink to one and green to another. Thus,  the perception of colour is dependent on vision, light, and individual interpretation. It also depends on the understanding of colour which involves physics, physiology, and psychology.

Therefore, the correct option is C.

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Answer:

218.02 mL

Explanation:

Data Given:

weight of the empty beaker = 49.03 g

weight of water and beaker = 267.05 g

density of water = 1 g/mL

Solution:

As we know that the volume that beaker hold is the volume of water that occupied by it.

For this first we have to find mass of the water in the beaker

This can be calculated by the subtraction of beaker's weight from the weight of beaker and water.

      weight of water (m) = total weight - weight of beaker

put values in the above formula

      weight of water (m) = 267.05 g - 49.03 g

      weight of water (m) = 218.02 g

To find volume we will use density formula

              d = m/v

rearrange the above equation to calculate volume

               v = m/d . . . . . . . (1)

put values in equation 1

            v = 218.02 g / 1 (g/mL)

            v = 218.02 mL

The volume that beaker hold = 218.02 mL

Explanation:

Chemical reaction

When two or more substances react and form some new substance it is called as chemical reaction .

There are so many reactions , out of which decomposition is also one type .

It is explained below :

Decomposition reaction

it is the type in which a reactant breaks up into its constituents  either by heating or passing current or in presence of light .

That is :  

(a) Photo decomposition (breaking in presence of light )  

Examples AgCl-----Ag+Cl₂

                (white )  (grey )

(B)Electrolytic decomposition : breaking by passing current  

Example : NaCl------Na+Cl₂

©Thermal decomposition : breaking by heating )

Example : Pb(No₃)₂-----PbO+NO₂+O₂

                                                                          (reddish brown gas )

ACTIVITY TO DEMONSTRATE : heating of ferrous sulphate  

FeSO₄.7H2O------FeSO₄+7H₂O

(GREEN )

FeSO₄-----------------heat -------Fe₂O₃+SO₂+SO₃

This question is done considering : Identify the type of reaction

2 Pb(NO3)2 – 2 PbO + 4 NO2 + O2

Answer:

Liquid thermometers can be limited by the type of liquid used. Mercury, for instance, becomes a solid at -38.83 degrees Celsius (-37.89 degrees Fahrenheit). Mercury thermometers cannot measure temperatures below this point.:

Mercury freezes at -38.9°C, which is equivalent to -37.22°F, making it the coldest temperature that can be measured using a mercury thermometer.

Mercury freezes at -38.9°C. To convert this temperature to Fahrenheit, we can use the formula: F = (C * 9/5) + 32. Plugging in the value of -38.9°C, we get: F = (-38.9 * 9/5) + 32 = -37.22°F. Therefore, the coldest temperature that can be measured using a mercury thermometer is -37.22°F.

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Answer:

4 moles of Nitrogen gas is produced.

Explanation:

Is in the picture. I used mole ratio.

Hope this helps!

Answer:

d = 283.68 g/mL

Explanation:

Density:

Density is equal to the mass of substance divided by its volume.

Units:

SI unit of density is Kg/m3.

Other units are given below,

g/cm3, g/mL , kg/L

Formula:

D=m/v

D= density

m=mass

V=volume

Symbol:

The symbol used for density is called rho. It is represented by ρ. However letter D can also be used to represent the density.

Here the unit given are gram/ milliliter. The given data shows that its density, because,

density = mass/ volume

d = m/v

d = 30.07 g/ 0.106 mL

d = 283.68 g/mL

The mass of water required to fill the flask is 33.17 g

Why?

To find the mass of water required to fill the flask we have to apply the weight by difference method.

It consists in determining the difference between the filled flask and the dry one. The difference is going to be the mass of water that was inside the flask, knowing that the total weight is the sum of the mass of the water and the dry flask.

Knowing that we can use the following equation:

[tex]massH_2O=Total Mass-MassDryBeaker=78.648g-45.48g=33.17g[/tex]

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Answer:

The manager sold the book shelf at $235.2

Explanation:

Since we have given that

Wholesale price of the book shelf = $147.00

But Gabriela's Furniture Store marks up all furniture by 60%.

So, Mark up value is given by

                                        = [tex]\frac{60}{100} \times 147[/tex]

                                        = [tex]\frac{8820}{100}[/tex]

                                        = $88.2

So, the new price that the manager sold the book shelf is given by

                                         = 147 + 88.2

                                       = $235.2

Therefore, the manager sold the book shelf at $235.2

Answer:

                     15.99 dm³

Explanation:

The molecular formula of Linoleic acid is C₁₈H₃₂O₂. As shown in attached figure, the Linoleic acid contains two double bonds hence we can say that in the Hydrogenation reaction of Linoleic acid 2 mole of H₂ are added across the two double bonds to make it saturated (Stearic acid).

The balance chemical equation for the hydrogenation of Linoleic acid is as follow:

                            C₁₈H₃₂O₂ + 2 H₂  →  C₁₈H₃₆O₂

Calculating moles of Linoleic acid:

                    Moles = Mass / M/Mass

                    Moles = 100 g / 280 g/mol

                    Moles = 0.357 moles Linoleic acid

Calculating moles of Hydrogen:

According to equation:

1 mole C₁₈H₃₂O₂ required  =  2 moles of H₂

So,

0.357 moles Linoleic acid will require  =  X moles of H₂

Solving for X,

                        X  =  2 moles × 0.357 moles / 1 mole

                        X  =  0.714 moles of H₂

Calculating volume of Hydrogen Gas:

Let us assume that the volume is calculated at standart temperature (273.15 K) and pressure (1 atm). We know that STP,

                         1 mole of gas occupies  =  22.4 dm³ of volume

So,

              0.714 moles of gas will occupy  = X dm³ of volume

Solving for X,

                     X =  22.4 dm³ × 0.714 moles / 1 mole

                     X =  15.99 dm³

Note: As the answer is not 17.28 dm³ so it means that the conditions for gas like temperature and pressure are different and are not mentioned in statement. Hence, if the conditions are known then one can use ideal gas equation i.e. PV=nRT to solve for volume.

Answer:

first.....lets calculate the molar mass of KClO4

39+35.5+16*4

39+35.5+64

=138.5g/mol

so that mean every mole have 138.5g...got that?

138.5g = 1mole

123g=x mole

123/138.5=x

x=0.888mol

Answer:

Number of moles = mass /molar mass

                              = 123 g/ 242.0111 g/mol

                                 = 0.508 mol

Explanation:

The [H+] in the acid rain which has a pH of 5.6 is Hydrogen ion which dissociates from the acidic Carbonic acid.

Explanation:

                              CO₂ + H₂O ----> H₂CO₃

                               H₂CO₃ ----------> [H+] + [HCO₃-]

Using the equation,

              pH = - log [H+] , we can solve for [H+] as following,

                           - pH = log [H+] ,

                             [H+] = 10-pH,

Exponentiating on both sides with base 10. The hydrogen ion concentration is,

[H+] = 10-5.6 = 0.0000025 = 2.51 × 10-6 M.

Answer:

Explanation:

[tex]\text{Let}\\\\x-\text{a volume of}\ 20\%\ \text{saline solution}\\\\y-\text{a volume of }\ 50\%\ \text{saline solution}\\\\p\%=\dfrac{p}{100}\\\\20\%=\dfrac{20}{100}=\dfrac{2}{10}=0.2\\\\50\%=\dfrac{50}{100}=\dfrac{5}{10}=0.5\\\\0.2x-\text{a volume of salt in }\ 20\%\ \text{saline solution}\\0.5y-\text{a volume of salt in }\ 50\%\ \text{saline solution}\\\\60mL-\text{a volume of}\ 28\%\ \text{saline solution}\\\\28\%=\dfrac{28}{100}=0.28[/tex]

[tex]0.28\cdot60mL=16.8mL-\text{a volume of salt in }\ 28\%\ \text{saline solution}\\\\\text{Equations}\\\\(1)\qquad x+y=60\\(2)\qquad0.2x+0.5y=16.8[/tex]

[tex]\left\{\begin{array}{ccc}x+y=60\\0.2x+0.5y=168&\text{multiply both sides by 10}\end{array}\right\\\left\{\begin{array}{ccc}x+y=60&\text{multiply both sides by (-2)}\\2x+5y=168}\end{array}\right\\\underline{+\left\{\begin{array}{ccc}-2x-2y=-120\\2x+5y=168}\end{array}\right}\qquad\text{add both sides of the equations}\\.\qquad3y=48\qquad\text{divide both sides by 3}\\.\qquad y=16[/tex]

[tex]\text{Put the value of}\ y\ \text{to the first equation:}\\\\x+16=60\qquad\text{subtract 16 from both sides}\\x=44[/tex]

B) 44 mL of the 20% solution and 16 mL of the 50% solution.

Here we used "Mixture Allegation" to determine the quantity of each solution:

Ist type of solution                           II nd type of solution

     20%                                                       50%

                                   28%

--------------------------------------------------------------------------------------

50%-28%                        :                         28%-20%

22%                               :                            8%

 11                                  :                             4

There is total quantity of 60 ml of solution.

So, Quantity of 20% solution in the mixture is provided by

[tex]\frac{11}{15} \times 60 = 11\times 4 = 44 ml[/tex]

And, Quantity of 50% solution in the mixture is provided by

[tex]\frac{4}{15} \times 60 = 11\times 4 = 16 ml[/tex]

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Explanation:

Significant figures

The significant figures (also known as the significant digits and decimal places) of a number are digits that possess certain  meaning .

It  includes all digits except: zeros

Rules to find significant figures

1.All non-zero digits are considered significant. For example, 23  has two significant figures.

2.Zeros in between two non-zero digits are significant: like in 202.1201  has seven significant figures.

3.Zeros to the left of the significant figures are not significant. For example, .000021 has two significant figures, zeros have no value .

4.Zeros to the right of the significant figures are significant.

That is the reason in number 5060 , it has 3 significant figures .

Answer:

Cells that support neurons