Structure and applications of poly(vinyl alcohol) hydrogels produced by conventional crosslinking or by freezing/thawing methods

Answer:

D.) K, Mn, As, Ar

Explanation:

The metalloids are located in the p-block on the periodic table and have a ladder-like arrangement.

The most commonly recognized metalloids are:

boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te)

Answer:

0.086

Explanation:

A 5.2 molal aqueous solution of methyl alcohol indicates that 5.2 moles of methyl alcohol are present in 1 kilogram (or 1000 g) of water. Water has a molecular weight of 18 g/mol.

(100g)/18g/mol=55.56 mol

5.2 mol/(5.2mol+55.56 mol)=0.086

The new temperature (in °C) of the gas, given the data is –148.20 °C

The new temperature of the gas can be obtained by using the combined gas equation as illustrated below:

P₁V₁ / T₁ = P₂V₂ / T₂

Since the volume is constant, we have:

P₁ / T₁ = P₂ / T₂

349.84 / 422.05 = 103.45 / T₂

Cross multiply

349.84 × T₂ = 103.45 × 422.05

Divide both side by 349.84

T₂ = (103.45 × 422.05) / 349.84

T₂ = 124.80 K

Subtract 273 from 124.80 K to express in degree celsius

T₂ = 124.80 – 273

T₂ = –148.20 °C

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The enthalpy of fusion for Al is 10.7 kJ/mol. -12.2 kJ is the energy change when 30.8 g of Al solidifies at 660°C.

The amount of energy needed to change 1 mole of substance under state change at constant temperature and pressure is called enthalpy of fusion. It is also known as Latent heat of fusion. Unit of enthalpy of fusion is kJ/mol.

To find the change in energy use this expression:

q = n ΔH

where

q = Energy change

n = number of moles

ΔH = Molar enthalpy

Number of moles (n) = [tex]\frac{\text{Given mass}}{\text{Molar mass}}[/tex]

                                  = [tex]\frac{30.8\ g}{26.98\ \text{g/mol}}[/tex]

                                  = 1.141 mol

Now put the values in above formula we get

q = - n ΔH                    [Negative sign is used because Al solidifies here]

  =  - (1.141 mol × 10.7 kJ/mol)

  = -12.2 kJ

Thus from the above conclusion we can say that The enthalpy of fusion for Al is 10.7 kJ/mol. -12.2 kJ is the energy change when 30.8 g of Al solidifies at 660°C.

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1.98 moles of Magnesium oxide were formed.

The balanced chemical equation is the equation in which the number of atoms on the reactant side is equal to the number of atoms on the product side in an equation.

Now write the balanced chemical equation

2Mg + O₂ → 2MgO

(2 × 24)          2 × (24 + 16)

48 g of Mg gives 80 g of MgO

To find the number of moles use the expression

Number of moles = [tex]\frac{\text{Given mass}}{\text{Molar mass}}[/tex]

                              = [tex]\frac{80}{40.3}[/tex]

                              = 1.98 mole

Thus from the above conclusion we can say that 1.98 moles of Magnesium oxide were formed.

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A first-order reaction is 81omplete in 264s.The half-life for this reaction (i) t 1/2 = =3.465×10 −3 s.to reach 95% Completion = 285 s.

To measure reaction rates, chemists initiate the reaction, measure the concentration of the reactant or product at different times as the reaction progresses,

For a 0-order response, the mathematical expression that may be employed to determine the half of life is: t1/2 = [R]0/2k. For a first-order reaction, the half of-existence is given by: t1/2 = zero.693/ok. For a 2d-order response, the method for the half-life of the response is: 1/okay[R]0

The 1/2-life of a response (t1/2), is the quantity of time needed for a reactant concentration to lower via half of compared to its initial awareness. Its software is used in chemistry and medicine to are expecting the awareness of a substance over time

Half of the lifestyles is the time required for exactly 1/2 of the entities to decay   50%.

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Suppose 110.0 mL of hydrogen gas at STP combines with a stoichiometric amount of fluorine gas and the resulting hydrogen fluoride dissolves in water to form 150.0 mL of an aqueous solution. 0.032 M is the concentration of the resulting hydrofluoric acid.

The balanced chemical equation is the equation in which the number of atoms on the reactant side is equal to the number of atoms on the product side in an equation.

Now write the balanced chemical equation

H₂ + F₂ → 2HF

An ideal gas is a gas that obey gas laws at all temperature and pressure conditions. It have velocity and mass but do not have volume. Ideal gas is also called perfect gas. Ideal gas is a hypothetical gas.

It is expressed as:

PV = nRT

where,

P = Pressure

V = Volume

n = number of moles

R = Ideal gas constant

T = temperature

Here,

P = 1 atm   [At STP]

V = 110 ml = 0.11 L

T = 273 K   [At STP]

R = 0.0821   [Ideal gas constant]

Now put the values in above expression

PV = nRT

1 atm × 0.11 L = n × 0.0821 L.atm/ K. mol × 273 K

[tex]n = \frac{1\ \text{atm} \times 0.11\ L}{0.0821\ \text{L. atm/ K. mol} \times 273\ K}[/tex]

n = 0.0049 mol

To calculate the concentration of resulting solution use the expression

[tex]C = \frac{n}{V}[/tex]

   [tex]= \frac{0.0049}{0.15}[/tex]  

   = 0.032 M

Thus from the above conclusion we can say that Suppose 110.0 mL of hydrogen gas at STP combines with a stoichiometric amount of fluorine gas and the resulting hydrogen fluoride dissolves in water to form 150.0 mL of an aqueous solution. 0.032 M is the concentration of the resulting hydrofluoric acid.

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The composition of a given pure compound is always the same no matter what the source of the compound.

A compound seems to be a substance that is entirely made of one kind of molecule.

Every component of compounds shares the same traits and features because of their homogenous makeup. However, because mixtures are composed of several sorts of chemicals, they frequently differ in terms of content, qualities, and samples.

Therefore, the composition of a given pure compound is always the same no matter what the source of the compound.

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Answer:

carbon atoms tend to make four bonds, each carbon atom will have the number of hydrogen atoms that are required for four bonds. This compound contains 16 hydrogen atoms for a molecular formula of C 8 H 16.

Explanation:

The product that is used on the natural nail prior to application to assist in adhesion and serves to chemically bond the enhancement product to the natural nail is known as nail primer.

A nail primer is a chemical agent used in esthetic centers before applying a colored polish to the nails and serves as an adhesive product.

The nail primers are also very useful for improving the cleaning efficiency of the product before its application.

Nail care products include different types of chemical formulations such as, for example, creams that reinvigorate the cuticle.

In conclusion, the chemical formulation employed on the natural nail that is capable of enhancing and also assisting adhesion is called the nail primer.

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The missing part of the equation is found to be 4/2He. Option A

The term nuclear equations have to do with the type of equation in which one type of nucleus is transformed into another sometimes by the bombardment or loss of a particle.

Now the full equation ought to be written as 7/3Li + 1/1H -----> 4/2He + 4/2He. This is because the total mass on the left is 8 and the total charge on the left is 4.

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Based on the data below, the elements that the star contains is a combination of Hydrogen and Helium. (Option A)

It is to be noted that Hydrogen is a simple atom with a straightforward spectrum. Aside from the three lines seen above, another in blue at 410 nm may be visible.

However, Helium, on the other hand, is a little more complicated than hydrogen, with one yellow line and a number in blue.

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Answer:

Radium Nitride

A radioactive element is radium. See what "radioactive" actually means.

Atoms make up the elements. Since most atoms are stable, they do not change over time. However, some of the heaviest atoms disintegrate and transform into different types. "Radioactivity" is the term for this breakdown or disintegration.

Each radioactive element releases rays that decay or disintegrate at a specific pace. There is no known way to speed up or slow this rate. Some changes happen quickly, some take longer, but no matter what, man cannot control the action.

In the case of radium, this decay would continue indefinitely until the radioactive material was ultimately converted to lead. For instance, in 1,590 years, half a gram of radium would transform into atoms with a lower atomic weight. Half of the remaining radium would transform after an additional 1,590 years, and so on until all of it turned into lead.

Attachment #1:

This is a revigator. It is a pot that was created specifically with radium, uranium, and other radioactive materials to contain water. When radioactivity was first discovered in 1912, people thought it was beneficial and "magical," similar to how homeopathic treatments are now. They would store water in it to allow it to absorb radiation, then they would drink the water. In the 1930s, several gadgets were subsequently recalled.

The enigmatic new radioactive elements captivated people's curiosity during the early 1900s. Although this starch didn't actually contain radium, it was given that name because of the rarity and beauty of radium. It was once thought of similarly to how titanium is now.

Madame Curie and her husband, Pierre Curie, made the discovery of radium. They were processing a ton of pitchblende, an ore that contains uranium. Although they were aware that the uranium was emitting invisible rays, they had the impression that there was another another, far more potent chemical present. They initially discovered polonium, another radioactive element, before successfully isolating a minute particle of radium.

The three types of rays that radium emits are alpha, beta, and gamma rays. Helium gas contains swiftly moving particles called alpha rays. In beta rays, the electrons move quickly. Gamma rays are similar to X-rays but typically more invasive. Every time one of these rays is emitted, its parent atom transforms into a different element. "Atomic transmutation" is the term for this transformation.

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The chemical formula of aluminum chloride is AlCl₃ and the  chemical formula of aluminum oxide is Al₂O₃.

The chemical formula of aluminum chloride is written as;

Al³⁺  + Cl⁻   → AlCl₃

The chemical formula of aluminum oxide is written as;

Al³⁺  + O²⁻   → Al₂O₃

Thus, the chemical formula of aluminum chloride is AlCl₃ and the  chemical formula of aluminum oxide is Al₂O₃.

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Answer:

pH = 7.01

Explanation:

The pH can be calculated using the formula:

pH = -log[H⁺]

In this formula, [H⁺] represents the concentration of H⁺. Since you have been given this value, you can easily find the pH.

pH = -log[H⁺]

pH = -log[9.71 x 10⁻⁸]

pH = 7.01

Answer:

212 000 yrs

Explanation:

15/16 decay means 1/16 is left

 how many halflives is this?

                    (1/2)^n = 1/16

                       n = 4   half lives

4 half lives * 53 000 yr/ half life = 212 000 yrs

Answer:

c. 212,000 years

Explanation:

got it right on edge:3

Dissolving sugar in water results in an increase in the entropy.

Hence, Option (D) is correct answer.

Measurement of randomness of a system is called entropy. It is an extensive property. It is a state function. Unit of entropy is JK⁻¹ mol⁻¹.

Now lets check all options one by one

Option (A): Freezing water

Freezing water decreases the entropy because here second law of thermodynamics does not violate.

So it is incorrect option

Option (B): Cooling water

Cooling water does not increases entropy because entropy increases when solid melts to give liquid.

So it is incorrect option

Option (C): Condensing water vapour

In Condensing water vapour the temperature of liquid phase decreases and thus kinetic energy decreases. The randomness will decrease and hence entropy will also decrease.

So it is incorrect option.

Option (D): Dissolving sugar in solute

In dissolving sugar in solute the solid dissociates to ions and  the randomness will increase and hence entropy will also increase.

So it is correct option

Thus from the above conclusion we can say that Dissolving sugar in water results in an increase in the entropy.

Hence, Option (D) is correct answer.

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As per Ideal gas equation, molar mass of the gas is 5.032 g/mo

We’ll begin by calculating the number of mole of the gas. This can be obtained as follow:

Volume (V) = 1.6 L

Temperature (T) = 287 K

Pressure (P) = 0.92 atm

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

Number of mole (n) =?

According to Ideal gas equation , PV = nRT

0.92 × 1.6 = n × 0.0821 × 287

1.472 = n × 23.5627

Divide by 23.5627

n = 1.176 / 23.5627

n = 0.0624 mole

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

Mass of gas = 0.314 g

Number of mole = 0.0624 mole

Mole = [tex]\frac{mass}{molar mass}[/tex]

0.0624 = [tex]\frac{0.314}{molar mass}[/tex]

Cross multiply

0.0624 × molar mass of gas = 0.314

Divide by 0.0624

Molar mass of gas =  [tex]\frac{0.314}{0.0624}[/tex]

Molar mass of gas = 5.032 g/mo

Therefore the Molar mass of gas is 5.032 g/mo

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At 55 mph, it takes about  228  feet to react to something you see and to bring the car to a complete stop.

It has taken as long as afootball field to stop your car at 55 mph ( 265 and 303 feet) and is assuming you were alert. If you drive at 55 mph on a dry , level pavement , your average stopping distance will be 265 feet . The stopping distance increases in the adverse conditions.

The car stops when both tire and the car have comes to a completely on rest point.

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Answer:

it would do wonders for the health of those using them and, by extracting energy from the fuel more efficiently, would be more environmentally sustainable too.

Answer:

R = 8.314 pKa*L/mol*K

The value for the ideal gas constant (R) is approximately 8.314 kPa·L/(mol·K).

To determine the value for the ideal gas constant (R) when pressure (P) is in kilopascals (kPa), temperature (T) is in kelvins (K), volume (V) is in liters (L), and amount of gas (n) is in moles, we need to use the appropriate units for R based on these measurements.

The ideal gas constant, R, can be expressed in various units. The most common units for R are:

R = 0.0821 L·atm/(mol·K) (atmospheres, liters, moles, and kelvins)

However, since you provided the measurements in kilopascals, liters, moles, and kelvins, we need to use a different value for R that is consistent with these units:

R = 8.314 kPa·L/(mol·K)

Therefore, when pressure is in kilopascals, volume is in liters, amount of gas is in moles, and temperature is in kelvins, the value for the ideal gas constant (R) is approximately 8.314 kPa·L/(mol·K).

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In the following redox reaction, the reducing agent is MnO2 (option D). Details about reducing agent can be found below.

A reducing agent in a redox reaction is any substance that reduces, or donates electrons to another, hence, it becomes oxidized.

According to this question, a redox reaction is given as follows: MnO2(s) + 4H+(aq) + 2Cl–(aq) = Mn2+(aq) + 2H2O(l) + Cl2(g)

As shown in the equation, MnO2 is oxidized into Mn2+, therefore, it is the reducing agent.

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9.17 milliliters (mL) of the acid are needed to completely neutralize the base in this reaction.

A neutralization reaction is a reaction between an acid and a base to produce a salt and water only.

The process of reacting given volume of acids or bases to determine the concentration or volume of either the acid or base required for neutralization is known as titration in volumetric analysis.

The formula to determine the volume of the acid required is given below:

[tex]\frac{C_{a}V_{a}}{C_{b}V_{b}} = \frac {N_{a}}{N_{b}}[/tex]

where [tex]V_{a[/tex] is the volume of acid required

[tex]V_{a} = \frac {C_{b}V_{b}N_{a}}{C_{a}N_{b}}[/tex]

Concentration of base, Cb = (3.51/74)/0.75 = 0.063 M

Vb = 50. 0 mL

Ca = 0.229 M

Na = 2

Nb = 3

Va = (0.063 * 50 * 2)/(0.229 * 3)

Va = 9.17 mL

In conclusion, the volume of the acid is determined from the concentration, volume and mole ratio of the reaction.

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Nitrogen gas reacts with oxygen gas to form dinitrogen tetroxide. When the equation is written and balanced, the sum of the coefficients is 3.

By catalytically oxidizing ammonia, nitrogen tetroxide is produced; steam is employed as a diluent to lower the combustion temperature. The ammonia is converted into nitric oxide in the initial step:

 4 NH3 + 5O2   →    6 H2O  + 4 NO

The gases are further cooled and the majority of the water is condensed; the created nitric oxide is then converted to nitrogen dioxide, which is dimerized into nitrogen tetroxide:

2 NO + O2 →2 NO2

2 NO2 ⇌ N2O4

Dinitrogen tetroxide is the chemical molecule N2O4, also known as nitrogen tetroxide (NTO) and occasionally amyl (typically among ex-USSR/Russian rocket engineers). It is a helpful reagent in the synthesis of chemicals. It and nitrogen dioxide combine to form an equilibrium combination. It has a 92.011 g/mol molar mass.

Dinitrogen tetroxide is a potent oxidizer that spontaneously reacts when it comes into touch with different types of hydrazine, making it the two popular bipropellants for rockets.

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Answer:

solvent

Explanation:

Water dissolves the substances, which become the solutes in the solution.

According to the 2010 U.S. Census, 37 percent of women had college degrees compared to approximately 35 percent of men.

In 1970 and early 1980, women have surpassed men in number of bachelor's degree or master's degree in united state.

The women gets more degree to gain financial benefits. The gap in earning is greater in female graduate and non- graduate as compare to male graduate and non-graduate. To give education to girls saves lives and builds stronger families, communication and economic too.

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1.001

120.0

Significant figures are used in science to determine the precision of a number. Depending on the decimal point, sig figs are counted in different ways.

Decimal Points

When counting sig figs, you always start at the first non-zero number. However, sometimes you start from the left, other times the right.

Remember to start counting at the first non-zero number.

For people in the Americas, there is a trick to remembering this.

This works because the Pacific ocean is to the left of the Americas, and the Atlantic is to the right.

4 Significant Figures

The number 1.001, has 4 significant figures. Since there is a decimal point, we start counting from the left. The first digit is not zero, so we count all four places as significant.

The number 120.0 also has 4 sig figs. Like the number above, we start counting from the left because of the decimal. The first digit on the left is not zero, so we once again count all 4 digits as significant.

Answer:

66 grams of carbon dioxide

C3H8+5O2=3CO2+4H2O

Their fossilized shells formed these limestone rocks, which, like Gubbio's mountains, were once at the bottom of the ocean. Now exposed, they represent over a million years of a geological time period known as the Cretaceous.

Walter Alvarez found that forming a distinct boundary between the limestone of the two periods was a thin layer of red clay. Immediately below this clay boundary, the Cretaceous limestone was heavily populated with a wide mix of the fossils of tiny marine creatures called foraminifera, or “foram” for short.

On the Atlantic Coast, outside the town of Zumaia, Dutch geologist Jan Smit was studying the forams from a different ancient sea. Their fossilized shells formed these limestone rocks, which, like Gubbio's mountains, were once at the bottom of the ocean.

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