Please I’m timed!!!!

If sec 0 = -7.3 find sin (0 - pi/2)

7.3
-7.3
-0.14
0.14

Accidental cosmic background radiation, remarkably uniform, billions of years ago.

what is radiation ?

Radiation is a form of energy that is emitted in the form of waves or particles. It is an invisible form of energy that travels through space. Radiation is present everywhere in the environment and is emitted from many sources, both natural and man-made.

Natural sources of radiation include the sun, rocks, soil, and the air. Man-made sources include nuclear power plants, medical devices, and X-ray machines. There are several forms of radiation including alpha, beta, and gamma radiation. Alpha radiation is made up of particles, while beta and gamma radiation consists of electromagnetic waves. Different types of radiation have different properties that make them useful in various applications. For example, gamma radiation is used in medical imaging.

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Answer:

Explanation:

An anion is a negatively charged ion, meaning it has gained one or more electrons. A cation is a positively charged ion, meaning it has lost one or more electrons. The charge of an ion can be determined by its atomic number, the number of protons it contains, and the number of electrons it contains. An anion will have more electrons than protons and a cation will have more protons than electrons. An anion will be attracted to positive charges, while a cation will be attracted to negative charges. Anions and cations can also be compared based on their size and shape. Anions are typically larger than cations, and they often have a spherical shape. Cations, on the other hand, are typically smaller and have a more angular shape.

The two mentioned gases have the same number of atoms as they are present at STP.

An atom is defined as the smallest unit of matter which forms an element. Every form of matter whether solid,liquid , gas consists of atoms . Each atom has a nucleus which is composed of protons and neutrons and shells in which the electrons revolve.

The protons are positively charged and neutrons are neutral and hence the nucleus is positively charged. The electrons which revolve around the nucleus are negatively charged and hence the atom as a whole is neutral and stable due to presence of oppositely charged particles.

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Answer:

Explanation:

1. Identify the elements present in the compound. The compound N2O3 contains two elements: nitrogen (N) and oxygen (O).

2. Determine the type of compound. N2O3 is an ionic compound, as it contains two different elements.

3. Write out the full name of the compound. The full name of the compound is dinitrogen trioxide.

4. Identify the subscripts. The subscripts indicate the number of atoms of each element in the compound. In this case, there are two nitrogen atoms (N2) and three oxygen atoms (O3).

5. Assign the proper name. The proper name for N2O3 is dinitrogen trioxide.

Answer:

the density of 10.002 g of water at 20°C in the units of g/mL is 0.998 g/mL

Explanation:

Density of 10.002g of water at 20°C in g/mL = 0.998 g/mL

Given that:

density of water at 20°C = 0.9982 g/mL

Density = mass / volume ---- ( 1 )

Where :  mass = 10.002 g

              Volume = ?

              Density = 0.9982 g/mL

∴ Volume = 10.002 / 0.9982   = 10.02 mL

back to equation ( 1 )

Density = 10.002 / 10.02 = 0.9982 g/mL ≈ 0.998 g/mL

The vapor pressure at 85.0°C of a solution prepared by dissolving 0.300 mol of liquid dibromoethane the vapor pressure at 85.0°C of a solution prepared by dissolving 0.300 mol of liquid dibromoethane is 164.83 torr.

The term vapor pressure is defined as the tendency of a material to change into the vapour state, and it increases with temperature.

For calculating mole fraction of C₂H₄Br₂ as follows

X C₂H₄Br₂ = moles of C₂H₄Br₂ / moles of C₂H₄Br₂ + moles of C₃H₆Br₂

= 0.3 / 0.3 + 1.80

= 0.14

For calculating mole fraction of C₃H₆Br₂ as follows:

XC₃H₆Br₂ =  moles of C₃H₆Br₂ / moles of C₂H₄Br₂ + moles of C₃H₆Br₂

= 1.80 / 2.1

= 0.85

For calculating total vapor pressure as follows:

P total = [ ( 0.14 × 127) + (0.85 × 173) ]

= 17.78 + 147.05

= 164.83 torr

Thus, The vapor pressure at 85.0°C of a solution prepared by dissolving 0.300 mol of liquid dibromoethane the vapor pressure at 85.0°C of a solution prepared by dissolving 0.300 mol of liquid dibromoethane is 164.83 torr.

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The mass in grams of water that are produced when 80. g of NaOH react with 73 g of HCl to form 117 g of NaCl and water is 36.0 g.

The equation of the reactions of sodium hydroxide and hydrochloric acid is given below:

NaOH + HCl ---> NaCl + H₂O

The mole ratio is 1 : 1 : 1 : 1

Moles of NaOH that reacted = 80/40

Moles of NaOH that reacted = 2 moles

Moles of HCl that reacted = 73/36.5

Moles of HCl that reacted = 2 moles

Moles of water produced will be 2 moles

Mass of water = 2 * 18 g/mol

Mass of water produced = 36.0 grams.

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IUPAC named for the compound shown here is 1- hydroxyl, 3- ethyl, hexane.

The International Union of Pure and Applied Chemistry is full form of IUPAC. It is important because it creates a standardized way to name chemical compounds in organic chemistry.

The International Union of Pure and Applied Chemistry recommends using the IUPAC nomenclature of organic chemistry to name organic chemical substances.

The rule of the first point of difference states that the series that includes the lowest number when the first difference occurs is the "lowest."

Thus, IUPAC named for the compound shown here is 1- hydroxyl, 3- ethyl, hexane.

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Two moles or 78 g of potassium metal reacts with water to give one mole or 2 grams of hydrogen gas. Then 20 g of K will give 0.51 g of hydrogen gas.

Metals especially alkali metals and alkaline earth metals are highly reactive towards air and water. By reacting with water these metals produces their corresponding hydroxides.

Potassium reacts with water forms KOH as written below:

[tex]\rm 2K + 2H_{2}O \rightarrow 2 KOH + H_{2}[/tex]

As per this reaction, 2 moles of K produces 1 mole of hydrogen

atomic mass of K = 39 g/mol

mass of 2 K = 78 g

mass of H₂ = 2g

Then mass of H₂ produced from 20 g of K is:

mass of H₂ = (20 × 2) /78 = 0.51 g

Therefore, 0.51 g of hydrogen gas is produced by 20 grams of potassium metal.

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An example of a biotic factor of an aquarium ecosystem is an  algae growing on the glass. Option B is the correct answer.

This refers to a living organism that shapes its environment. The examples of biotic factor that make up fresh water ecosystem are: aquatic plants, fish, amphibians,fungi, bacteria, and protists. and algae.

The biotic factors are gropped into : producers, consumers, and decomposers.

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Answer:

The molar mass of an unknown gas can be determined using the concept of effusion. Effusion is the process of a gas passing through a small hole or porous partition. The rate of effusion of a gas is inversely proportional to the square root of its molar mass. This relationship is described by the Graham's law of effusion.

Explanation:

Graham's law of effusion states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass.

R = k √M

Where R is the rate of effusion, k is a constant, and M is the molar mass of the gas.

If we know the rate of effusion of COCl2 and the rate of effusion of an unknown gas and we know that the unknown gas effuses at a rate 1.5 times the rate of COCl2.

R unknown = 1.5 * R COCl2

We can use this information to find the molar mass of the unknown gas.

M = (R COCl2 / (1.5 * R unknown) )²

If we know the molar mass of COCl2, we can substitute it in the equation and solve for the molar mass of the unknown gas.

It's worth noting that this problem requires you to know the molar mass of COCl2 which is not provided in the question. And also it's important to know that the values of the constant k in the equation for the different gases are not the same, so you need to use the same gas as reference.

The bond length for NH3, NF3, and PF3 can be compared based on their molecular geometry and the strength of the chemical bonds between the atoms.

NH3 has a bond angle of 107 degrees and a bond length of 1.01 Angstroms. This is due to the presence of a lone pair of electrons on the Nitrogen atom which causes the bond angles to deviate from the ideal tetrahedral angles of 109.5 degrees.

NF3 has a bond angle of 107 degrees and a bond length of 1.1 Angstroms. This is due to the presence of a lone pair of electrons on the Nitrogen atom which causes the bond angles to deviate from the ideal tetrahedral angles of 109.5 degrees.

PF3 has a bond angle of about 101 degrees and a bond length of 1.48 Angstroms. This is due to the fact that the Fluorine atoms are larger than the Nitrogen atoms of NH3 and NF3, and the bond between Phosphorus and Fluorine is stronger and shorter than the bond between Nitrogen and Hydrogen or Nitrogen and Fluorine.

In summary, the bond length of NH3 and NF3 is shorter than that of PF3 due to the smaller size of Nitrogen atoms compared to Phosphorus and the presence of lone pairs on Nitrogen atoms. The bond between Nitrogen and Hydrogen or Nitrogen and Fluorine is weaker than the bond between Phosphorus and Fluorine.

The power sector is targeted for the application of hydrogen fuel cells.

This type of fuel produces electricity through the combination of hydrogen and oxygen atoms. The hydrogen reacts with oxygen across an electrochemical cell and produces electricity, water, and heat in a very small quantity.

Hydrogen-powered fuel cell electric vehicles doesn't have any carbon emission or greenhouse gases such as carbon dioxide etc which depletes the ozone layer and causes global warming.

It emit none of these harmful substance and only emits water and warm air which makes it a very clean fuel thereby causing a reduction in pollution and reducing the risk of respiratory diseases.

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The statements about substances X and Y are true are Y is the solvent in this solution, The presence of Y in the solution lowers the vapor pressure of X and if Y were not present, there would be more X particles in the gas above the liquid solution. Therefore, option A, B and C are correct.

A mixture in which one substance dissolves in the other is called a solution. The solute is the substance that dissolves. The solvent is the substance that does not dissolve. Salt water is an example of a solution.

In a mixture called a solution, every component is well combined. Solutions can contain solids, liquids, and gases and are regarded as homogenous mixes. A solute and a solvent makeup a solution. Any substance that dissolves in a solvent is referred to as a solute.

Thus, option A, B and C are correct.

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Answer: 2:3

Explanation: The question is phrased annoyingly. NH3 to H2 means we need to keep our numbers correct.

2NH3 -> 2 mol of NH3.

3H2 -> 3 mol H2.

NH3/H2 = NH3 to H2.

2:3.

2 mol NH3

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

3 mol H2.

2:3, not 3:2.

Concentration of 20cm³ of sulphuric acid that neutralize 25cm³ of 0.100M of KOH, basically is NaOH. 2NaOH + H2SO4 → Na2SO4 + H2O.

What is sulphuric acid?

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Answer: 31.2 g

Explanation: Given,

2.40 x 10^23 molecules of SO3

number of moles (n) = given number of molecules / total number of molecules

n = 2.4 x10^23/ 6.023 x 10^23

n = 0.39 moles

mass  = molecular mass x number of moles(n)

mass in grams  = 80 (Molecular mass of SO3) x 0.39

mass in grams  = 31.2 g

The wavelength  you get for an angle of incidence of 30 degrees and reflection angle of 7 degrees is

2.3633166* 10^{-4}mm

Generally, To calculate the wavelength, you would need to use the equation for diffraction grating:

mλ = d(sin θi - sin θr)

Where

Plugging in the given values:

1λ = (1/1600 mm)(sin 30° - sin 7°)

Solving for λ:

λ = (1/1600 mm)(sin 30° - sin 7°)

λ = 2.3633166* 10^{-4}mm

This equation gives you the wavelength in the first-order diffraction

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The mole fraction of oxygen in the cylinder, given that the cylinder contains 8.2 moles of oxygen and 8.22 moles of lead is 0.499

Mole fraction is simply defined as:

Mole fraction of subtance = Mole of sunstance / total mole

Next, we shall determine the total mole in the cylinder. Details below:

Total mole = Mole of oxygen + mole of lead

Total mole = 8.2 + 8.22

Total mole = 16.42 moles

Finally, we shall determine the mole fraction of oxygen in the cylinder. Details below:

Mole fraction of oxygen = mole of oxygen / Total mole

Mole fraction of oxygen = 8.2 / 16.42

Mole fraction of oxygen = 0.499

Thus, we can conclude from the calcultions made above that the mole fraction of oxygen is 0.499

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Complete question:

A cylinder contains 8.2 mol of oxygen and 8.22 mol of lead. What is the mole fraction of oxygen in the cylinder?

Answer:

In X2​O3​,. Percentage of oxygen by weight = 31.58. Percentage of X by weight = 68.42. Let the atomic weight of X = x. 2x+482x​×100 = 68.42. ∴ x = 51.99.

Explanation/solution in image

The Cr-incorporated Ni catalyst shows optimized OH-binding as well as H-binding energies for facilitating water dissociation and improving HER activity in alkaline media.

Developing efficient and inexpensive electro catalysts for the hydrogen evolution reaction (HER) in alkaline water electrolysis plays a key role in renewable hydrogen energy technology.

The trends in HER activity with respect to the binding energies of Ni-based thin film catalysts by incorporating a series of oxophilic transition metal atoms. It was found that the doping of oxophilic atoms enables the modulation of binding abilities of hydrogen and hydroxyl ions on the Ni surfaces, leading to the first establishment of a volcano relation between OH-binding energies and alkaline HER activities.

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Answer:

11000

Explanation:

85.3 has 3 significant figures

21.489 has 5 significant figures

0.0059 has 2 significant figures ( as zeros on the left are not significant)

The answer is always rounded off to the least number of decimal places given in the question. Here the least number is two significant figures.

Therefore;

(85.3 - 21.489)/0.0059

= (63.811)/0.0059

= 10815.42

As we have to round off the answer to two significant figures:

= 11000

Answer:In (a). 1st blank will be 1

2nd blank will be 4

3rd blank will be 3

(b).1-1

2-3

3-1

4-2

(c).1-1

2-12

3-12

4-11

(d).1-2

2-3

3-2

4-4

Explanation:

Answer:

Explanation:

5.342 x 10 the power of 7

The pressure on a cold winter day would be 16.03 psi.

The pressure law state that the pressure of a gas at constant volume is directly proportional to its temperature. This law can be mathematically expressed as follows:

[tex]P_1/T_1 = P_2/T_2[/tex]

Where [tex]P_1[/tex] = initial pressure of the gas, [tex]T_1[/tex] = initial temperature, [tex]P_2[/tex] = final pressure, and [tex]T_2[/tex] = final temperature.

In this case, [tex]P_1[/tex] = 33 psi, [tex]T_1[/tex] = 35 [tex]^oC[/tex] and [tex]T_2[/tex] = -17 [tex]^oC[/tex]. What we are looking for is [tex]P_2[/tex].

[tex]P_2[/tex] = [tex]P_1.T_2/T_1[/tex]

    = 33 x -17/35

     = 16.03 psi

In other words, at constant volume and without leakage, the pressure in the tire on a cold winter day when the temperature is -17 [tex]^oC[/tex] would be 16.03 psi.

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The pressure of a gas is directly proportional to its temperature and inversely proportional to its volume.

PV/T = PV/T

(1.00atm * 3.5 L)/ 273k = (P * 0.50L)/(39.1 + 273k)
Do some simple algebra and you will get
P = 8.0 (Note that there should be 2 sigfigs)

Saturation concentration refers to the highest concentration of a substance that can exist in a solution in equilibrium with its solid or gaseous form. A saturation concentration less than 5 but greater than 2 is a relatively broad range, and many different chemicals could fall within this range depending on the conditions of the solution.

Examples of chemicals with saturation concentration less than 5 but greater than 2 include:

Calcium carbonate, which has a saturation concentration of around 3.5 g/L at room temperature and normal pressure

Iron(III) hydroxide, which has a saturation concentration of around 3.5 g/L at room temperature and normal pressure

Potassium chloride, which has a saturation concentration of around 3.5 g/L at room temperature and normal pressure

Ammonium chloride, which has a saturation concentration of around 2.5 g/L at room temperature and normal pressure

Sodium sulfate, which has a saturation concentration of around 3.5 g/L at room temperature and normal pressure

It's important to note that these are just examples, the saturation concentration of a chemical can vary depending on temperature, pressure, and other factors.

The mass percentage of C is 7.8 %

The method for expressing a concentration is known as mass percent. The solution components of a given solution can be defined by the mass percentage.

The molar mass of CCL4 is carbon 12.0107g + 4*chlorine 35.453g = 153.823g.

The number of moles of carbon in CCL4 can be found by dividing the mass of carbon (12.0107g) by the molar mass of carbon (12.0107g/mol).

The mass percentage of carbon in CCL4 can be found by multiplying the number of moles of carbon by the molar mass of CCL4 and dividing by the total mass of CCL4, then multiplying by 100.

So, mass percentage of C = (12.0107g / 153.823g) * 100 = 7.8 %

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Answer:

isolation, loneliness or psychological distress

Explanation:

In addition, older people are more likely to experience events such as bereavement, or a drop in socioeconomic status with retirement. Sadly these stressors can result in isolation, loneliness or psychological distress in older people. Mental health has an impact on physical health and vice versa.

The beaker of orthoxylene was put inside a sealed tank containing orthoxylene gas at 142. degree C and 893. torr will have the same amount of liquid inside it after ten minutes because the system is a closed system as none of the liquid's vapor escapes.

The correct option is the same amount.

A closed system allows energy to enter and exit but not matter to enter or exit. About a closed system is a covered pot on the burner. Both matter and energy cannot enter or leave an isolated system. A thermos or cooler is about as isolated a system as there is.

The beaker of orthoxylene that was put inside a sealed tank containing orthoxylene gas at 142 degrees C and 893 torr is a closed system.

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