What is a hypothesis?

A. analysis based on an observation.

B. a proposed answer to a question.

C. a conclusion based on analysis.

D. data gathering during an experiment.​

Answer:

Water

Explanation:

one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. Water is a tasteless, odorless liquid at ambient temperature and pressure. Which is known to be crystal blue.

Answer:

well I t could be in liquid form or in air form

Explanation:

Answer:

There are several ways to know if a chemical change has occurred. The following is an indication that a chemical change has occurred

1. Change of composition - wood turning to ash when burned.

2. Change of color - For example, during titration, we know that the reaction has occurred by a change in colour from orange to pink when we used methyl orange as indicator., rusting of iron.

3. Change in temperature or energy, such as the production (exothermic or loss endothermic) of heat.

4. The decomposition of organic matter for example, the decay of dead plant or animal

5. Light and/or heat given off: For example, potassium react explosively with water releasing a large amount of heat

6. When the change is difficult to reverse. For example, after burning wood to produce ash, we can not get back the wood again.

The theory of Plate Tectonics describes the forces and motion of Earth's plates. This theory explains the movement of the Earth's crust on a semi-fluid layer beneath, resulting in geographical phenomenon like earthquakes and mountain formations.

The theory which describes the motion of and the forces driving the Earth's plates is D. Plate Tectonics. The Plate Tectonics theory encompasses the concept of the Earth's crust being made up of large pieces, known as plates, that float on a semi-fluid layer underneath. Over time, these plates shift, bump into each other, or even slip beneath one another, causing many of the Earth's major geographical features such as mountains, valleys, earthquakes and volcanoes. This theory has greatly contributed in our understanding of the Earth's geology, and it complements A. First Law of Motion and B. Third Law of Motion, which are principles from Physics that describe general motion and forces, not specifically Earth's plates.

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Answer: 1.15x10²³ molecules C

Explanation: solution attached:

Convert mass of C to moles using its molar mass then multiply to the Avogadro's number.

Explanation:

This given reaction is a chemical reaction that is : Double decomposition reaction .

In this reaction , there is a reaction between two compounds in which they mutually interchange their ions .

That is :

AB +CD ---> AC +BD

Similarly in this we have :

Na3PO4+KOH—->NaOH + K3PO4

The double decomposition reaction is either :

Precipitation reaction : resulst in the formation of ppt .

Neutralization reaction : results in the formation of neutral substance

Answer:

                     The chemical formula of Formaldehyde is H₂CO and the structural formula is attached below,

                     The chemical formula of Ammonia is NH₃ and the structural formula is attached below,

FORMALDEHYDE:

                              As shown in structure, there are two different types of bonds in formaldehyde,

        (i) C-H Bond

        (ii) C-O Bond

So the electronegativity difference of these bonds are,

(i) C-H Bond

           Electronegativity of Carbon      =  2.5

           Electronegativity of Hydrogen  =  2.1

                                                               _______

           Electronegativity Difference  =       0.4 (non-polar bond)

(ii) C-O Bond

           Electronegativity of Oxygen      =  3.5

           Electronegativity of Carbon       =  2.5

                                                               _______

           Electronegativity Difference  =       1.0   (polar bond)

AMMONIA:

                              As shown in structure, there is one type of bond in ammonia, and that is N-H bond

So the electronegativity difference in this bond is,

N-H Bond

           Electronegativity of Nitrogen      =  3.0

           Electronegativity of Hydrogen    =  2.1

                                                               _______

           Electronegativity Difference  =        0.9   (polar bond)

The answer can be solved using Gay-Lussac's law. Relevant values are plugged into the formula where P1/T1=P2/T2 and solving for P2 yields 0.890 atm.

This is a chemistry problem related to the Gas Law, specifically, Gay-Lussac's law, which states that the pressure of a gas is directly proportional to its temperature, provided its volume remains constant.

Since the problem does not mention a change in volume, we can assume it's constant. The formula for Gay-Lussac's law is P1/T1=P2/T2, where P is the pressure, T is the temperature, and subscripts 1 and 2 refer to the initial and final conditions.

We are given: P1 = 0.750 atm, T1 = 45 C = 318.15 K (converted to Kelvin using the formula K = C + 273.15), and T2 = 105 C = 378.15 K. We are asked to solve for P2.

Plug these values into the formula: (0.750 atm / 318.15 K) = P2 / 378.15 K.  By cross-multiplying and dividing, we solve for P2: P2 = (0.750 atm x 378.15 K) / 318.l5 K = 0.890 atm.

None of the given choices match the calculated answer, suggesting there may be a typo or error in the question.

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Answer:

Pangaea

Alfred Wegner

plate tectonics

Explanation:

What did Earth look like 250 million years ago? The continents of Earth were clustered together in formation that a scientist named Pangaea.The scientist that named "Pangaea" was a German scientist by the name of Alfred Wegner. He theorized that "Pangaea" split apart and the different landmasses, or continents, drifted to their current locations on the globe. Wegener's theories of plate movement became the basis for the development of the theory of plate tectonics.

Final answer:

To react completely with 4.5 moles of FeO, 81.0 grams of aluminum are required, based on the stoichiometry of the chemical equation and the molar mass of aluminum.

Explanation:

To find out how many grams of aluminum are needed to react completely with 4.5 mol of FeO, we need to first examine the specific reaction between aluminum (Al) and iron(III) oxide (Fe₂O₃). The balanced chemical equation is:

2 Al(s) + 3 FeO(s) → 3 Fe(s) + Al₂O₃(s).

From this equation, we can deduce that 2 moles of Al are needed to completely react with 3 moles of FeO. Therefore, for 4.5 moles of FeO, the molar ratio of Al to FeO (2:3) indicates that (4.5 mol FeO) × (2 mol Al / 3 mol FeO) = 3 mol Al are required.

The molar mass of Al is 27.0 g/mol. To convert moles of Al to grams, we multiply the moles of Al needed by the molar mass of Al:

3 mol Al × 27.0 g/mol = 81.0 g Al.

Thus, 81.0 grams of aluminum are needed to react completely with 4.5 mol of FeO.

Answer: 12.3 g H2O

Explanation: solution attached:

The maximum mass of NaCl is 0.54 g.

Explanation:

The reaction can be represented with the following equation:

                    HCl + NaOH ---->  NaCl + H2O

According  to  the  equation,  equal  amounts  of  chemical  agents  and  resultant  products  (in moles) participate in this reaction.

The amount of hydrochloric acid is as follows:

                            [tex]v_{HCl} = \frac{m_{HCl} }{M_{HCl} }[/tex] [tex]= \frac{m_{HCl} }{A_{H} + A_{Cl} }[/tex]

                                     = 1.1 / (1 + 35.46)

                            [tex]v_{HCl}[/tex]  = 0.030 moles.

where m is the mass,

           A is the atomic mass of an element.

The amount of sodium hydroxide is as follows:

                           [tex]v_{NaOH} = \frac{m_{NaOH} }{M_{NaOH} } = \frac{m_{NaOH} }{A_{Na} + A_{O} + A_{H} }[/tex]

                                        = 0.420 / (23 + 16 + 1)

                                        = 0.0105 moles.

Since  the  amount  of  sodium  hydroxide  exceeds  the  amount  of  hydrochloric  acid,  the maximum amount of each substance participating in the reaction is v = [tex]v_{HCl}[/tex] = 0.030 moles.

Therefore, the maximum amount of water that can be produced is as follows:

                             [tex]m_{H2O} = M_{H2O} \times v_{H2O} = (2A_{H} + A_{O} ) \times v[/tex]

                                        = (2 [tex]\times[/tex] 1 + 16) [tex]\times[/tex] 0.030 = 0.54 g.

          The maximum mass of NaCl is 0.54 g.

The number of protons in an isotope of an element is determined by its atomic number. The element Chromium (Cr) has an atomic number of 24, so all its isotopes, including Cr-50, Cr-52, Cr-53, and Cr-54, contain 24 protons.

The element symbol Cr represents the element Chromium. The number of protons in any isotope of an element is determined by the atomic number, not the isotope number. Chromium has an atomic number of 24, so all isotopes of Chromium, including Cr-50, Cr-52, Cr-53, and Cr-54, contain 24 protons.

The number of protons in an isotope of an element is determined by its atomic number. The element Chromium (Cr) has an atomic number of 24, so all its isotopes, including Cr-50, Cr-52, Cr-53, and Cr-54, contain 24 protons.

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Answer: Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus. 

so C would seems to be right.

Explanation: The energy of an electron depends on the size of the orbit and is lower for smaller orbits. Radiation can occur only when the electron jumps from one orbit to another. The atom will be completely stable in the state with the smallest orbit, since there is no orbit of lower energy into which the electron can jump.

Answer:

d

Explanation:

Just did it on edge

Answer: 51g

Explanation:

n = m/M (where 'n' is the number of moles, 'm' is the mass and 'M' is the molar mass)

n = 3 moles (Given in the question)

M = 17

(This is because nitrogen has a relative mass of 4u and hydrogen has a relative mass of 1u)

We can rearrange the equation and get that

n * M = m

Therefore, 3 * 17 gives you the mass of 3 moles of ammonia

Which is 51g.

Answer: 51g

Explanation:

To solve for the mass of 3 moles of ammonia(NH3), let's get the mass of 1 mole of ammonia(NH3)

1mole of ammonia (NH3) = 14 +(3x1) = 17g.

Therefore,

3 moles of NH3 = 3 x 17 = 51g

Answer:

                     D) There are fewer grams of HCl than Mg(OH)₂

Explanation:

                    The balance chemical equation for given reaction is as;

                        Mg(OH)₂ + 2 HCl → MgCl₂ + 2 H₂O

Step 1: Calculate Moles of Mg(OH)₂ and HCl as;

Mg(OH)₂:

              Moles  =  Mass / M.Mass

              Moles  =  25.3 g / 58.319 g/mol

              Moles  =  0.433 moles of Mg(OH)₂

HCl:

              Moles  =  Mass / M.Mass

              Moles  =  22.5 g / 36.460 g/mol

              Moles  =  0.617 moles of HCl

Step 2: Find out Limiting reagent as;

According to equation,

                   1 mole of Mg(OH)₂ reacted with  =  2 moles of HCl

So,

             0.433 moles of Mg(OH)₂ will react with  =  X moles of HCl

Solving for X,

                     X  =  0.433 mol × 2 mol / 1 mol

                    X =  0.866 moles of HCl

This means for given amount of Mg(OH)₂ we require 0.866 moles of Hcl while, we are only provided with 0.617 moles of HCl hence, HCl is the limiting reagent and will control the final yields of products.

Step 3: Find out Moles of MgCl₂ produced;

According to equation,

                   2 moles of HCl produced  =  1 mole of MgCl₂

So,

             0.617 moles of HCl will produce  =  X moles of MgCl₂

Solving for X,

                     X  =  0.617 mol × 1 mol / 2 mol

                    X =  0.3085 moles of MgCl₂

Step 4: Calculate Mass of MgCl₂ as;

                   Mass  =  Moles × M.Mass

                   Mass  =  0.3085 mol × 36.46 g/mol

                   Mass =  11.24 g of MgCl₂

Answer:

A) The amounts of both reactants are given.

Explanation:

The amounts of both reactants are given. You cannot tell which reactant will be used up first. Calculate the mass of product that can be produced from the amount of the first reactant; calculate the mass of product that can be produced from the second reactant. Compare the two. The limiting reactant produces the least product.

The mass of 187 liters of CO2 gas is 0.36 g.

Explanation:

The molecular weight of CO2 is 44 g / mol.

1 kg of CO2 = 1000 g [tex]\times[/tex] ( 1 mole / 44 g) = 22.7 mole of CO2.

By using the ideal gas equation,

                                    PV = nRT

                                      V = nRT / P

where P represents the pressure,

          V represents the volume,

          T represents the temperature,

          R represents the ideal gas constant,

          n represents the amount of substance.

                                   V = (22.7)[tex]\times[/tex](0.0821)[tex]\times[/tex](273.15) / 1

                                   V = 509.6 L of CO2 at STP

            Mass = (187 L of CO2 gas) / (509.6 L of CO2 at STP)

                       = 187 / 509.6

            mass = 0.36 g

To find the mass of 187 liters of CO2 gas at STP, we calculate the number of moles using the molar volume of 22.4 L/mol and then multiply by the molar mass of CO2 (44.01 g/mol) to get a mass of approximately 367.34 grams.

The mass of 187 liters of CO2 gas at STP (standard temperature and pressure) can be calculated by first determining the number of moles of CO2. The molar volume of an ideal gas at STP is 22.4 liters, so by dividing the volume of the gas by the molar volume, we can get the numbers of moles.

Here's the calculation:

Number of moles of CO2 = Volume of CO2 / Molar Volume at STP = 187 L / 22.4 L mol-1

Number of moles = 8.348 moles (rounded to three decimal places)

The molar mass of CO2 is 44.01 g/mol, so now we can calculate the mass:

Mass of CO2 = Number of moles×  Molar Mass = 8.348 moles ×44.01 g/mol

Mass = 367.34 g (rounded to two decimal places)

The mass of 187 liters of CO2 gas at STP is approximately 367.34 grams.

Answer:

density

Explanation:

There are, mainly, three states of matter (solid, liquid and gas). These can be defined differently from the other according to their physical properties. In order to do this, scientists use the word "density" to compare their properties.

Solid has a higher density compared to liquid and gas. This is because its particles are tightly packed. Liquid has a lower density when compared to solid because its particles are loosely arranged. Gas has the lowest density among the three. This means that the gas particles have a very big space, thus rising to a higher kinetic energy.

Thus, this explains the answer.

The same volume, pressure, and temperature. Option C

Equal volumes of gases at equal temperatures and pressures contain an equal number of molecules, according to Avogadro's principle. Thus, it can be presumed that two gas samples have the same volume, pressure, and temperature if they contain the same number of molecules and no information about changes in circumstances is given.

The relationship between pressure (P), volume (V), and temperature (T) for a given amount of gas (n) is described by the ideal gas law, which is compatible with this.

Answer:

Square root { 2g * Delta-y * /m}

Explanation:

it is as shown in the attached file.

Note that the expression "2gΔy" with the square root can be represented as: [tex]\[2g\sqrt{\Delta y}\][/tex]

The expression [tex]\[2g\sqrt{\Delta y}\][/tex] represents a mathematical formula involving the square root of the change [tex](\Delta)[/tex] in the variable y. Here:

- 2 is a constant multiplier,

- g is a constant (possibly representing the acceleration due to gravity),

-  [tex]\sqrt{\Delta y}[/tex] denotes the square root of the change in y.

It is a concise way to express a quantity that involves a constant, the square root, and a change in a variable. The specific interpretation would depend on the context of the problem or equation in which it appears.

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Ethyne is prepared by using water and calcium carbide in the laboratory.

Explanation:

Acetylene is conveniently prepared in the laboratory by the action of water(H₂O) on calcium carbide (CaC₂). Calcium carbide in turn is obtained by heating the mixture of coke and lime stone in an electric furnace.

CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂

Ethyne gas prepared in the lab using the above method may contain impurities like H₂S, PH₃, AsH₃, NH₃etc. The gas is purified by bubbling it through acidified copper sulfate solution.

Answer:

0.9911 mol

Explanation:

Answer:

MgCl2

Explanation:

Lattice energy will be higher on ion with higher charge, or smaller size. A higher charge means it will have a stronger force. Smaller size ion will have less distance.  

Magnesium has +2 charge and located in the third row, make it strongest of these three. Natrium will be the second strongest even though its charge is +1, the same as Kalium. Natrium has smaller size as it is on the third row, compared to Kalium that was in the fourth row.

MgCl2 would have the most negative lattice energy due to the higher charge of Mg²⁺ and its smaller ionic radius.

Lattice energy refers to the energy required to separate one mole of an ionic compound into its gaseous ions. It is determined by the charges and sizes of the ions involved. The more negative the lattice energy, the stronger the ionic bond.

The most negative lattice energy among NaCl, KCl, and MgCl2 is found in MgCl2. This is due to the higher charge of Mg²⁺ compared to Na⁺ and K⁺, as well as its smaller ionic radius. These factors result in stronger electrostatic attractions between the ions, leading to a more negative lattice energy.

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Answer:

Lead (/ˈlɛd/) is a chemical element with the symbol Pb

Answer: 2 NH3 => 2 N + 3 H2

Explanation: The equation is now balanced.

2 atoms of N in both the reactant and product side and 6 atoms for H on both sides.

The wavelength of the light emitted is 5 x [tex]10^{-3}[/tex] nm

Explanation:

The wavelength of light from an LED with a frequency of 60 Hz is not in the visible spectrum and would be extremely long, measuring 5 x 10^15 nm, which falls within the range of radio waves.

To determine the wavelength of light emitted by an LED lightbulb with a frequency of 60 Hz, we must use the relationship between the speed of light, frequency, and wavelength. The equation we use is c = λν, where c is the speed of light in vacuum (approximately 3 × 108 m/s), λ is the wavelength, and ν is the frequency. However, a frequency of 60 Hz would result in a wave that is not within the visible light spectrum but rather in the range of radio waves, and its wavelength would be extremely long compared to visible light wavelengths measured in nanometers.

To calculate the wavelength in meters, we divide the speed of light by the frequency:

λ = c / ν

λ = (3 × 108 m/s) / (60 Hz)

λ = 5 × 106 m

To convert this to nanometers (nm), knowing that 1 m = 109 nm, we multiply by 109:

λ = 5 × 106 m × 109 nm/m

λ = 5 × 1015 nm

This wavelength is much larger than the wavelengths for light in the visible spectrum, which are typically between 380 nm and 750 nm. Consequently, the wavelength of 60 Hz frequency light cannot be represented in nanometers as it falls outside the visible range.

The correct answer is (B) This represents a chemical change only.

The fact that a gas is produced in a new and different substance indicates a chemical change. Chemical changes denote the formation of new substances having their own set of chemical qualities. When heat is applied to the substance, it undergoes a chemical reaction giving birth to a given gas.

This transformation entails the rearrangement of atoms and the breaking or formation of chemical bonds. Physical changes, on the other hand, do not alter the chemical composition of a substance. They have changes in physical properties like shape, size, or state of matter without actually forming new substances.

Since the production of another gas indicates a chemical change, the correct statement amidst these options is that the scenario reflects such (option B).

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Answer:

B. (Linear graph with positive slope)

Explanation:

The picture above showing that  

1. T2 is higher than T1

2. V2 is higher than V2

From this, we can conclude that the relationship for temperature (T) and volume(V) is positive. That means a higher temperature will result in a higher volume.  

Since the relationship positive, the graph will have a positive slope. We can't prove if the graph should be linear or exponential since we don't have the exact number of the experiment.

Answer:

B.

Explanation:

Final answer:

DNA is packaged into a structure called a chromosome inside cells. In prokaryotes, supercoiling helps in this process, while in eukaryotes, DNA wraps around histone proteins to form nucleosomes and further condenses into chromatin fibers, ultimately forming chromosomes.

Explanation:

When the DNA molecule folds, coils, and supercoils to fit inside a cell, it forms a structure known as a chromosome. In prokaryotic cells, like E. coli, DNA supercoiling helps to fit the large DNA molecule into a very small space. In eukaryotic cells, the process is more complex, involving the winding of DNA around histone proteins to form nucleosomes, which look like 'beads on a string.' These nucleosomes further coil into a 30-nm chromatin fiber. During cell division, the chromatin fibers condense even further to form the tightly-packed chromosomes visible under a microscope.

The degree of DNA supercoiling can vary, resulting in DNA that is either under-wound or over-wound. Proteins like topoisomerases are involved in maintaining the supercoiled structure of chromosomes, which is crucial for efficient DNA replication and transcription. This intricate packaging allows DNA, which can be up to 2 meters long in humans, to fit within the tiny nucleus of a cell.

Explanation:

Combination reaction

It is a reaction in which some substances or reactants combine to form a single substance or we can all it as single product .

Like : A + B --> C+D

This combination can be between a element and a element like :

H₂ +O₂--> H₂O

It can be between element and a compound like :

SO₂ + O₂---> SO₃

It can be between a compound and a compound like :

H₂O + CO₂---> H₂CO₃

In the above asked question , the combination is between Cu and a sulphur that is element and a element that is :

Cu + S ---> CuS

                 (copper sulphide )