Classify each of the following as either a physical change or a chemical change.
(a) Dissolving sugar in water
(b) Crushing rock salt
(c) Burning sulfur
(d) Digesting a chili dog

Answer:

Na2SO4

Explanation:

Chemistry operates on the principle of 'like dissolved like'. This implies that polar solvents dissolve polar substances while nonpolar solvents dissolve nonpolar substances.

This is because, dissolution of a substance in a solvent is as a result of intermolecular interaction between solute and solvent.

Since Na2SO4 is purely an ionic substance and CCl4 is purely a nonpolar solvent, Na2SO4 is least soluble in CCl4.

Answer:

Cis configuration is more stable

Explanation:

Generally the is configuration of cycloalkenes is more thermo-chemically stable than the trans-configuration  double bonds, because the latter causes twists in the ring, resulting in higher strain.

This also mean that there is a greater force of repulsion between cis molecules (little r no twists).

I hope you find this explanation was clear and helpful.

Answer:

75416 ft/min

(857 mi/h) x (5280 ft/h ÷ 1 mi / 1h ) x (1h x 1 ft ÷ 60 min x 1 ft)

Explanation:

Conversion of 857 mi/h to feet /second.

We'll begin by converting 857 mi/h to ft/h.

This is illustrated below:

Recall:

1 mi/h = 5280 ft/h

Therefore,

857 mi/h = 857 x 5280 = 4524960 ft/h

857 mi/h = 4524960 ft/h

Finally, we shall convert 4524960 ft/h to ft/min.

This can be obtained as follow:

Recall:

1 ft/h = 1/60 ft/min

Therefore,

4524960 ft/h = 4524960 x 1/60 = 75416 ft/min

4524960 ft/h = 75416 ft/min

Therefore, 857 mi/h is equivalent to 75416 ft/min.

To solve the above question in a shorter for we simply do the following:

(857 mi/h) x (5280 ft/h ÷ 1 mi/1h ) x (1h x 1 ft ÷ 60 min x 1 ft)

Answer:

5.22 atm

Explanation:

The following data were obtained from the question:

Number of mole (n) = 2 moles

Volume (V) = 10 L

Temperature (T) = 45 °C

Pressure (P) =?

Next, we shall convert 45 °C to Kelvin temperature. This can be obtained as follow:

Temperature (K) = Temperature (°C) + 273

T (K) = T (°C) + 273

T (°C) = 45 °C

T(K) = 45 °C + 273

T (K) = 318 K

Finally, we shall determine the pressure of the gas by using the ideal gas equation as shown below:

Number of mole (n) = 2 moles

Volume (V) = 10 L

Temperature (T) = 318 K

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

Pressure (P) =.?

PV = nRT

P x 10 = 2 x 0.0821 x 318

Divide both side by 10

P = (2 x 0.0821 x 318) /10

P = 5.22 atm

Therefore, the pressure of the gas is 5.22 atm

Answer:

41.2 lb/gal

Explanation:

Step 1: Given data

Density of iodine: 4.94 g/mL

Step 2: Convert the mass to grams

We will use the conversion factor 1 lb = 454 g.

4.94 g/mL × (1 lb / 454 g) = 0.0109 lb/mL

Step 3: Convert the volume to gal

We will use the conversion factors 1 gal= 3.785 L and 1 L = 1,000 mL.

0.0109 lb/mL × (1,000 mL/1 L) × (3.785 L/1 gal) = 41.2 lb/gal

Explanation:

Initial temp = 28 °C

Final Temp = ?

Heat = 184 J

mass = 5 g

c = 4.184 joule/gram °C

The relationship between these parameters is given by the equation;

H = mCΔT

ΔT = H / mC

ΔT = 184 / 5(4.184)

ΔT = 184 / 20.92

ΔT = 8.8 °C

ΔT = Final Temp - Initial Temp

Final Temp = Initial Temp + ΔT

Final Temp = 28°C  + 8.8 °C

Final Temp = 36.8°C

Answer:

1.51 × 10⁻⁵

Explanation:

Step 1: Given data

pKa value: 4.82

Step 2: Write the reaction for the acid ionization of butanoic acid, HC₄H₇O₂

Butanoic acid is a weak acid that ionizes according to the following equation.

HC₄H₇O₂(aq) ⇄ C₄H₇O₂⁻(aq) + H⁺(aq)

The acid ionization constant for this reaction is Ka

Step 3: Calculate the value of the ionization constant for butanoic acid

We will use the following expression.

pKa = -log Ka

Ka = antilog -pKa = antilog -4.82 = 1.51 × 10⁻⁵

Answer:

A polysaccharide (n) can be formed by linking several monosaccharides through glycosidic linkages.

Explanation:

Polysaccharides are carbohydrates or complex carbohydrates, where monosaccharides join with glucosidic bonds to form a more complex structure that would be the polysaccharide.

An example of a polysaccharide is starch, or glycogen.

Starch is found in many foods such as potatoes or rice, and glycogen is a form of energy reserve of our organism housed in muscles and liver to fulfill locomotion, physical activity, and other activities that consist of glycolysis.

Polysaccharides are degraded in our body by different stages, and several enzymes unlike monosoccharides or disaccharides, since they have more unions and a more complex structure to disarm in our body and thus assimilate it.

Polysaccharides are also part of animal structures, such as insect shells or nutritional sources, among others.

Answer:

XY₃

Explanation:

We have cations of the X³⁺ type and anions of the Y⁻ type. For a compound to be formed, it has to be electrically neutral, that is, it must have the same number of positive charges and negative charges so that the final charge of the compound is zero. In this case, the compound would be neutral if it had 1 atom of X³⁺ and 3 atoms of Y⁻. The resulting chemical formula would be XY₃.

Answer:

Vicinal dihalide

Explanation:

Dihalide in which the halogens are attached on adjacent carbons are called  Vicinal  dihalides.

They are prepared by reaction between halogen and alkyne and alkene. For example,  1,2-dichloroethane which is given by the reaction between ethylene and chlorine.

Answer:

stupidddd guhhhhhuiijui

Answer:

b. Predicting your horoscope

Explanation:

Pseudoscience refers to claims that are scientifically misleading and do not follow the scientific method. For example, imagine someone claims a certain drug will make you live forever. This is an example of pseudoscience. It has not been tested using the scientific method and it is misleading.

The scientific method follows this general structure.

1. Ask a question

2. Do background research

3. Construct a hypothesis

4. Test your hypothesis

5. Analyze data and draw a conclusion

6. Communicate your results. (Was your hypothesis correct?)

Finding a new star, dating the age of a fossil, and finding new uses for a drug all are processes that use the scientific method. Predicting your horoscope is not a science and it has not been proven using the scientific method.

An example of pseudoscience is " predicting your horoscope".

The term "pseudoscience" refers to claims that something is both true and scientific but are somehow incompatible well with the scientific process.

A horoscope would be a representation of the Sun, Moon, planets, astrological aspects, and various critical angles at the time of the occurrence, such as that of the period of a person's birth, using an astrological chart as well as a diagram.

Therefore, An example of pseudoscience is " predicting your horoscope".

Hence, the correct answer will be option (b).

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Answer:

The additional concentration of nitrogen in the river water due to the farmer's fertilizer is 0.0629 milligrams per liter

Explanation:

The mass of the fertilizer the farmer applies = 1705 kg

The percentage of nitrogen contained in the fertilizer = 10%

Therefore;

The mass of nitrogen contained in the fertilizer = 10% of 1705 kg = 10/100 × 1705 kg

The mass of nitrogen contained in the fertilizer = 10/100 × 1705 kg = 170.5 kg

The percentage of the fertilizer that washes into the river that runs through the farm = 15.0%

The mass of the fertilizer that washes into the river = 15/100 × 170.5 = 25.575 kg = 25575 g = 25575000 mg

The volume of water that flows through the farm = 0.455 cubic feet per second

The volume of water that flows through the farm in a year = 0.455 ft³ × 60 × 60 × 24 × 365 = 14348880 ft³ = 406,315.03 m³ = 406,315,034 l

The number of moles of nitrogen = Mass of nitrogen/(Molar mass of nitrogen)

Molar mass of nitrogen =14.0067 g/mol

Therefore;

The number of moles of nitrogen = 25575 kg/(14.0067 g/mol) = 1.825.912 moles

The additional concentration of the nitrogen in moles = 1.825.912 moles/(406,315,034 l) = 4.49 ×   10⁻⁶ mol/liter

The additional concentration of the nitrogen in milligrams of nitrogen per liter of water = 25575000/406,315,034 = 0.0629 milligrams of nitrogen per liter.

Therefore, the additional concentration of nitrogen in the river water due to the farmer's fertilizer = 0.0629 milligrams per liter

Answer:

324.46 amu

3.33 × 10⁻³ mol

Explanation:

(a) Calculate the molecular mass of quinine, C₂₀H₂₄N₂O₂

We will add the mass of each atom times the number of each atom in a molecule.

20 × C + 24 × H + 2 × N + 2 × O

20 × 12.01 amu + 24 × 1.01 amu + 2 × 14.01 amu + 2 × 16.00 amu

324.46 amu

(b) Calculate the number of moles of quinine in 1.08 g of quinine

The molar mass of quinine is 324.46 g/mol.

1.08 g × (1 mol/324.46 g) = 3.33 × 10⁻³ mol

Answer:

157 mL

Explanation:

Step 1: Given data for 2-chloro-2,3-dimethylbutane

Density (ρ): 0.878 g/mL

Mass (m): 138 g

Volume (V): ?

Step 2: Calculate the volume of the liquid required

The density of a compound is equal to its mass divided by its volume. We will use the following expression.

ρ = m / V

V = m / ρ

V = 138 g / (0.878 g/mL)

V = 157 mL

Answer:

Use a commercially produced charcoalfilter

Explanation:

Water found in streams, depressions and ground water must be contaminated with pathogenic microorganisms. The methods of disinfection using iodine or bleach or boiling the water for about two minutes and then filtering it with a clean cloth will effectively remove the microorganisms.

However, charcoal filters do not eliminate microorganisms from water hence this method is not acceptable in this case.

Answer:0.3348%

Explanation:

Answer:

A- Perform an experiment

Explanation:

Answer:

Electron pair geometry- tetrahedral

Molecular geometry- Trigonal Pyramidal

Explanation:

PCl3 has four electron domains on the outermost shell of the central atom in the molecule. This implies that it has a tetrahedral electron pair geometry according to Valence Shell Electron Pair Repulsion theory.

These four electron pairs are composed of three bond pairs and one lone pair. The presence of a lone pair of electrons leads to a trigonal pyramidal molecular geometry due to electron pair repulsions.

Answer:

If the pressure in the tire is low, then the tire lost air pressure because air is escaping through a hole in the tire.

Explanation:

The tire will lose air from a puncture in the tire, rather than the the second hypothesis saying tires do not lose air naturally.

Answer:

1) If the pressure in the tire is low, then the tire lost air pressure because air is escaping through a hole in the tire

Explanation:

I JUST DID IT

Answer:

The solutions are classified according to their ability to scatter light rays.

We can't just use this property because some true solutions also contain undissolved solute.

Explanation:

Tyndall effect refers to the ability of a solution to scatter light rays. True solutions do not scatter light rays while false solutions scatter light rays.

Colloid particles are not large enough to be seen with naked eyes unlike suspensions. We should not confuse a colloid with a suspension because in a suspension, the dispersed solutes are seen with naked eye.

Answer:

a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.

Explanation:

a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.

Answer:

d

Explanation:

you just cant

The law of conservation of matter defines the preservation of the mass of the reactant and the product. All the matter in the universe is bound to follow the law. Thus, option D is correct.

The law of conservation of matter or mass is the principle that states how the mass of the reaction system remains constant no matter what the reaction is. For any closed system, the mass can't change when undergoing changes.

When wood is burned for fire, water is frozen for ice, and magnesium chloride decomposes to produce chloride and magnesium then, the masses of the reactant and the product remain constant. There may be a chance that the mass seems to decrease in a reaction but it is due to changes in the phase of matter and no actual mass is lost.

Therefore, option D. none of these fails the law of conservation of matter.

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Answer: • Phe can undergo oxidation to form Tyr.

• The Ala side chain does not form hydrogen bonds with other amino acids.

• Thr and Ser are polar amino acids.

• Lysine has one stereocenter (chiral center).

Explanation:

Amino acids are simply organic compounds which are known to contain carboxyl and amine functional groups and the main elements that are found in an amino acid are oxygen, carbon, hydrogen, and nitrogen.

The true statements about amino acids are:

• Phe can undergo oxidation to form Tyr.

• The Ala side chain does not form hydrogen bonds with other amino acids.

• Thr and Ser are polar amino acids.

• Lysine has one stereocenter (chiral center).

It should be noted that Methionine is not a thiol but rather a thio ether. Also, proline is simply a neutral amino acid and the statement that proline has an overall charge at physiological

pH(7.4) is false.

Answer:

In the mid-19th century Claude Bernard was also influential, especially in bringing the scientific method to medicine. In his discourse on scientific method, An Introduction to the Study of Experimental Medicine (1865), he described what makes a scientific theory good and what makes a scientist a true discoverer.

Explanation:

Answer:

[tex]3.427 \times {10}^{3} [/tex]

Answer:

Chemistry will help us solve many future problems, including sustainable energy and food production, managing our environment, providing safe drinking water and promoting human and environmental health.

Explanation:

Answer:

It basically does nothing

Explanation:

But I guess it teaches yout o not mix things or do things that harm people or the earth

Answer:

pH = 4.58

Explanation:

The reaction of NaOH with acetic acid, CH₃COOH occurs as follows:

NaOH + CH₃COOH → CH₃COO⁻Na⁺ + H₂O

Moles that react:

NaOH = 10mL = 0.010L * (0,240mol / L) = 0.0024 moles NaOH

CH₃COOH = 50.0mL = 0.050L * (0.120mol / L) = 0.0060 moles CH₃COOH

That means after the reaction you will have:

CH₃COOH: 0.0060 mol - 0.0024 mol = 0.0036 moles

CH₃COO⁻Na⁺: 0.0024 moles

in solution, you will have the mixture of a weak acid (Acetic acid), with its conjugate base (sodium acetate, CH₃COO⁻Na⁺). And pH of this buffer can be determined using H-H equation:

pH = pKa + log [A⁻] / [HA]

For Acetic buffer pKa = 4.76:

pH = 4.76 + log [CH₃COO⁻Na⁺] / [CH₃COOH]

Where [] is molarity of each species or moles

Replacing:

pH = 4.76 + log [0.0024 moles] / [0.0036 moles]

Answer:

ΔH = 125.94kJ

Explanation:

It is possible to make algebraic sum of reactions to obtain ΔH of reactions (Hess's law). In the problem:

1. 2W(s) + 3O2(g) → 2WO3(s) ΔH = -1685.4 kJ

2. 2H2(g) + O2(g) → 2H2O(g) ΔH = -477.84 kJ

-1/2 (1):

WO3(s) → W(s) + 3/2O2(g) ΔH = 842.7kJ

3/2 (2):

3H2(g) + 3/2O2(g) → 3H2O(g) ΔH = -716.76kJ

The sum of  last both reactions:

WO3(s) + 3H2(g) → W(s) + 3H2O(g)

ΔH = 842.7kJ -716.76kJ

The enthalpy change (ΔH) for the reaction is 125.94kJ.

Hess's Law:

The Hess's law states that the total enthalpy change during a complete chemical reaction is the same regardless of the path taken by the chemical reaction.

It is possible to make algebraic sum of reactions to obtain ΔH of reactions (Hess's law).

It is given that:

1. 2W(s) + 3O₂(g) → 2WO₃(s) ΔH = -1685.4 kJ

2. 2H₂(g) + O₂(g) → 2H₂O(g) ΔH = -477.84 kJ

On dividing equation 1. by - 1/2 for simplification we get:

W(s) + 3/2 O₂(g) → WO₃(s)  ΔH = 842.7kJ....................(a)

On dividing equation 2. by  3/2 for simplification we get:

3H₂(g) + 3/2O₂(g) → 3H₂O(g) ΔH = -716.76kJ...................(b)

On adding equations (a) and (b)

WO₃(s) + 3H₂(g) → W(s) + 3H₂O(g)

ΔH = 842.7kJ -716.76kJ

ΔH = 125.94kJ

The enthalpy change for the reaction is 125.94 kJ.

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