The light intensity of a source is 100 candelas. The illuminance on a surface is 4 lux. How far is the surface from the source?

A. 7 meters
B. 6 meters
C. 4 meters
D. 5 meters

Answers

Answer 1
The correct answer is D. 5 meters.
Answer 2
Answer : Option D) 5 metersExplanation :

To find the luminous intensity this formula is used;

Luminous intensity = illuminance ×  [tex]radius ^{2}[/tex]

∴ Lv = Ev × [tex] r^{2}[/tex]

We know the luminous intensity is 100 candelas and the illuminance is 4 lux.

∴ 100 = 4 x  [tex] r^{2}[/tex]

∴ 100/4 =  [tex] r^{2}[/tex]

∴ 25 =  [tex] r^{2}[/tex]

∴ r =√25 = 5 meters

Therefore, the surface will be at a distance of 5 meters from the source.


Related Questions

How many electrons are transferred in the ionic bond between sodium and chlorine in nacl?

Answers

From the periodic table, we can find that:
Sodium has 11 electrons with a configuration of (2,8,1)
Chlorine has 17 electrons with a configuration of (2,8,7)

Based on this, we can see that sodium needs to lose one electron to become stable with valence shell having 8 electrons.
On the other hand, chlorine needs to gain one electron to become stable with valence shell having 8 electrons.

In sodium chloride, the sodium donates this one electron to chlorine forming an ionic bond so they both become stable.

Answer:

1

Explanation:

Just got it right on the quiz.

That is the exchange to fill.

Hope this helps.

1.64 mol of nickel at 150.13ºC is placed in 1.00 L of water at 25.09ºC. The final temperature of the nickel-water mixture is 26.34ºC. What is the specific heat of nickel?

a. 0.439 J K-1 mol-1
b. 0.554 J K-1 mol-1
c. 2.28 J K-1 mol-1
d. 25.7 J K-1 mol-1
e. 31.6 J K-1 mol-1

Answers

Heat gained or released by a system can be calculated by multiplying the given mass to the specific heat capacity of the substance and the temperature difference. It is expressed as follows:

Heat = mC(T2-T1) 

When two objects are in contact, it should be that the heat lost is equal to what is gained by the other. From this, we can calculate the what is being asked in the problem. We do as follows:

Heat gained = Heat lost
m C (Tf-Ti) = - m C (Tf-Ti) 
Since what is aksed is the specific heat capacity in units of J/mol-K, we change m into n which is the number of moles of a substance.
1.64 C (150.13 - 26.34) = (1000 /18.02) (4.18 x 18.02 )(26.34 - 25.09)
C = 25.7 J / mol-K <----------OPTION D

What volume is needed to make a 4.0 molar solution holding 12 moles of solute? 3.0 liters 48 liters 12 liters 4.0 liters

Answers

Hey there ! :

Number of moles ( solute ) = 12 moles

Molarity of solution = 4.0 M

Therefore:

M = n / V

4.0 = 12 / V

V = 12 / 4.0

V = 3.0 liters

Answer A

Answer: Option (a) is the correct answer.

Explanation:

Molarity is defined as the number of moles present in a liter of solution.

Mathematically,       Molarity = [tex]\frac{\text{no. of moles}}{volume}[/tex]

Since, it is given that molarity is 4.0 molar or 4.0 m/L and no. of moles is 12 moles.

Therefore, calculate volume as follows.

                      Molarity = [tex]\frac{\text{no. of moles}}{volume}[/tex]

                         4.0 m/L = [tex]\frac{12 moles}{volume}[/tex]

                      volume = 3 L

Hence, we can conclude that volume of the given solution is 3 liters.

A mixture of pure agcl and pure agbr is found to contain 60.94% ag by mass. what are the mass percents of cl and br in the mixture?

Answers

Final answer:

To calculate the mass percentages of Cl and Br in a mixture of AgCl and AgBr with 60.94% Ag by mass, we need additional data to determine the individual masses of Cl and Br. Without it, we cannot provide precise percentages.

Explanation:

The question is about calculating the mass percents of chlorine (Cl) and bromine (Br) in a mixture of silver chloride (AgCl) and silver bromide (AgBr) that contains 60.94% silver (Ag) by mass. The molar mass of silver (Ag) is 107.87 g/mol, for AgCl it is 143.32 g/mol (107.87 g/mol + 35.45 g/mol for Cl), and for AgBr it is 187.77 g/mol (107.87 g/mol + 79.90 g/mol for Br).

To find the mass percentages of Cl and Br in the mixture, we will first assume we have 100 grams of the mixture. Given the percent of silver, we can calculate the mass of silver in the mixture, which should be 60.94 grams. The remaining mass will be the combined mass of Cl and Br. However, without additional information such as the mass or molar ratios of AgCl to AgBr, we cannot precisely divide the remaining mass between Cl and Br. If such data were available, the mass percentages of Cl and Br could be found by calculating their individual masses and dividing by the total mass of the mixture, then multiplying by 100.

If you have a solid like ice (solid water), which of the following substances below would most closely resemble the structure of ice? indium cadmium quartz topaz

Answers

The correct option is QUARTZ. Quartz and ice belong to the hexagonal crystal group. They both have four axes, three of these axes are equal in length at an angle of 120 degree from one another and the last axis is either longer or shorter at a right angle to the other axes.

substance which allows energy to pass through it

Answers

A substance which allows energy (heat or electricity) to pass through it is known as a conductor.

These substances usually have free electrons which allows the charges to flow easily in the substance, thus, transferring energy.

Other substances which do not have free electrons and do not allow energy to pass through them are known as insulators.

He approximate molar concentration of several chemicals are given. find the ph of each. use the calculator and round to the nearest tenth, if necessary. oven cleaner: [h+] = 10−13 ph = water: [h+] = 0.0000007 ph = blood: [h+] = 0.00000004 ph = vinegar: [h+] = 0.0063 ph =

Answers

Answer:

oven cleaner: ph=13

water: ph=6.2

blood: ph=7.4

vinegar ph=2.2

Explanation:

got it right on ed

Final answer:

The pH values for the given solutions are calculated using the formula pH = -log[H+], where [H+] is the concentration of hydrogen ions. The pH values for an oven cleaner, water, blood, and vinegar are found to be 13.0, 7.2, 7.4, and 2.2 respectively.

Explanation:

To calculate the pH of a solution, we use the formula pH = -log[H+]. Here [H+] represents the molar concentration of hydrogen ions in moles per liter (M).

Oven cleaner: With [H+] = 10-13 M, we find pH as follows:

pH = -log(10-13) = 13.0

Water: For [H+] = 0.0000007 M or 7×10-7M:

pH = -log(7×10-7) = 7.2

Blood: Given [H+] = 0.00000004 M or 4×10-8M:

pH = -log(4×10-8) = 7.4

Vinegar: With [H+] = 0.0063 M:

pH = -log(0.0063) = 2.2

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The atomic number of this element is 9 and its mass is 20. how many neutrons does this element have?

Answers

Hey there!

n = A - Z

n = 20 - 9

n = 11

Answer:

11 neutrons

Explanation:

Mass no. = 20

atomic no. = 9

no. of neutrons = mass number - atomic number

                          =   20 - 9

                          =     11 neutrons

4 NH3 + 6 NO → 5 N2 + 6 H2O. How many moles of NO are required to completely react with 2.45 mol NH3? Show all of your work as well as the answer with the proper units.

Answers

6 mol NO - 4 mol NH₃
x mol NO - 2.45 mol NH₃

x=2.45*6/4=3.675≈3.68 mol

Mole is equal to the Avogadro's constant. The 3.675 moles of NO is required to completely react with 2.45 mole of Ammonia.    

Mole:

One mole is the unit of measurement of small particles like ions, atoms , and molecules. It is equal to the Avogadro's constant.

Given reaction,

[tex]\bold{4 NH_3 + 6 NO \rightarrow5 N_2 + 6 H_2O}[/tex]

Means 4 moles of Ammonia react with 6 moles of NO in reaction. the molar ratio of ammonia and NO is 4:6.

Hence,

Moles of NO required

[tex]\Rightarrow\bold{\frac{6}{4} \times 2.45 = 3.675 mole}[/tex]          

Hence, we can conclude that the 3.675 moles of NO is required to completely react with 2.45 mole of Ammonia.    

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What reactions are responsible for the glow and heat from the sun? nuclear fission nuclear fusion chemical reactions atomic disintegration?

Answers

Nuclear Fusion is the answer to the question who posted.

Nuclear Fusion is the answer to your question 

True or False no two elements have the same atomic number.

Answers

the answer to your question is true :)

According to the collision theory what two factors must be true to successfully result in a reaction

Answers

Explanation:

According to collision theory, more is the number of collisions between the particles of reactants more will be the rate of a reaction.

Two important factors of collision theory are as follows.

Sufficient energyOrientation

Sufficient energy: Molecules participating in a chemical reaction should have sufficient amount of energy so that they can overcome activation energy barrier and participate effectively in the reaction.

Orientation: Collision between the molecules should take place with proper orientation so that they successfully result in the formation of products.

According to the collision theory, the two factors that must be true for a reaction to occur are sufficient energy and proper orientation of reactant particles.

What is the collision theory of reactions?

The collision theory states that a reactant molecules must collide effectively with energy greater than or equals to activation energy for products to be formed.

According to the collision theory, the two factors that must be true are:

reactant molecules must be oriented properly the reactant molecules must have sufficient energy

Therefore, sufficient energy and proper orientation of particles is necessary for product formation.

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Calculate the percent ionic character of a chemical bond between beryllium and fluorine

Answers

Final answer:

The percent ionic character of a chemical bond, such as between beryllium and fluorine, can be determined using the difference in electronegativity between the two elements based on Pauling's scale. Most bonds exhibit partial ionic character, as they fall within the spectrum between purely ionic and purely covalent.

Explanation:

The percent ionic character of a chemical bond refers to the degree to which the bond exhibits ionic properties. In an ideal ionic bond, electrons are completely transferred from one atom to another. However, in reality, most bonds fall within the spectrum between purely ionic and purely covalent, exhibiting partial ionic character.

In the case of the bond between beryllium and fluorine, you can determine the percent ionic character by making use of Pauling's electronegativity values. First, you would calculate the difference in electronegativity between the two elements. Then, you use this difference to estimate the percent ionic character based on Pauling's scale.

For example, consider the hypothetical molecule HCl mentioned in the reference. Supposed that HCl was completely ionic, its molecular dipole moment was calculated to be 6.09 D. The experimentally measured bond moment, however, turned out to be 1.03 D. The percent ionic character was hence calculated as the bond moment divided by the theoretical fully ionic bond moment, multiplied by 100%. The result was 17%.

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calcium, magnesium, and phosphorus are all examples of

Answers

Calcium, magnesium, and phosphorus are all examples of minerals, or more concrete macrominerals (minerals that the human body needs in large amounts).
These three mineral compose the most of the the body’s mineral content (98%) and play important roles in various biochemical reaction at cellular level and metabolic functions.

Methanol is an important solvent. it is also an important starting material for the synthesis of other molecules. most methanol today is obtained from the

Answers

CO + 2H₂ → CH₃OH

Methanol is synthesized from carbon monoxide and hydrogen.

How many moles of electrons are required to reduce one mole of nitrogen gas (N2) to two moles of nitrogen ions (N3-)?

Answers

Start by writing the atoms balance:

[tex] N_{2} -\ \textgreater \ 2N^{3-} [/tex]

Now, determine the change of oxidation states:[tex] N_{2} [/tex] has oxidation state 0, so each N has to gain 3 electrons to become [tex] N^{3-} [/tex].

That, means that you need 6 electrons to balance the charges, resulting in:

[tex] N_{2} + 6 e^{-} -\ \textgreater \ 2 N_{3-} [/tex]

And the answer is 6 mole of electrons.

Draw a fatty acid chain that is 8 carbons long and is unsaturated

Answers

Fatty acid => hydrocarbon chain + carboxilic group => CnHm-COOH

8 carbons long => C - C - C - C - C - C - C - C - COOH

unsaturated => double bonds

=> CH3-CH=CH-CH2-CH2-CH2-CH2-CH2 - COOH: 8 carbon chain, one double bond, carboxylic group.

What net ionic equation can be derived from this complete ionic equation? 2fe3+(aq) + 6cl– (aq) + 6na+(aq) + 3co32– (aq) → fe2(co3)3(s) + 6cl– (aq) + 6na+(aq)?

Answers

So, in order to get the net ionic equation, we consider only the ions that reacted in the total ionic equation. We use these ions to get the net ionic equation.

Examining the total ionic equation provided, we will find that the only ions that reacted are the 2fe3+(aq) and the 3co32– (aq) ions which reacted together forming fe2(co3)3(s).

Based on this, the net ionic equation will be:
2Fe3+ (aq) + 3CO32- (aq) -----> Fe2(CO3)3 (s) 

Carbon monoxide poisoning is sometimes mistakenly identified as what?

Answers

When we breathe red blood cells bond to the oxygen but when we inhale carbon monoxide (CO), it sticks to red blood cells and block the oxygen and suffocation occurs. It is also known as “Silent Killer”.

Headaches, nausea and fatigue are some of early symptoms of carbon monoxide poisoning. It is sometimes mistakenly identified as “Flu”. Because this gas cannot be detected at home. It is produced by common household appliances, if not proper ventilated, such as water heaters, generators, cars etc.

Carbon monoxide poisoning and acute toxicity are related and often confused due to similar symptoms such as headache, weakness, and even death.

Carbon monoxide poisoning occurs due to inhaling excessive levels of carbon monoxide (CO), which can lead to symptoms like headache, dizziness, weakness, and even death. This poisoning is sometimes mistakenly identified as acute toxicity due to exposure to carbon monoxide.

Loss of consciousness, arrhythmias, seizures, and even death can result from large CO exposures.Long-term complications may include chronic fatigue, memory issues, and movement problems.

25 g of ethyl alcohol is dissolved in 100 ml of water (density = 0.99993 at 20 oc). what is the % w/w for the ethyl alcohol in the resulting solution?

Answers

Percentage by mass is the amount in mass of a component in a mixture per 100 unit of mass of the total mixture. Percentage by mass is the same as  %w/w. We can determine this by dividing the mass of the solute with the total mass of the mixture. However, from the problem statement, we are given the volume of the water so there is a need to convert this value to mass by using the density of water. We calculate as follows:

Mass of solution = 100 mL (0.99993 g/mL) water + 25 g EtOH
Mass of solution = 124.993 g solution

%w/w = 25 g / 124.993 g x100
%w/w = 20% of EtOH

Which type of storage facility is assumed to be safe for long term storage of nuclear waste products

Answers

An example would be the Yucca Mountain Nuclear Waste Repository.

Answer:

Deep geological disposal method

Explanation:

A deep geological disposal method is the most efficient method in disposing of the waste materials produced from a nuclear plant. These materials are disposed at a depth of usually about 200 to 1000 m below the surface and also from 1500 m to 5500 m below the surface. And it has to be below the groundwater level so that it does not contaminate it. So necessary precautionary measures are needed to be taken.

This method is used for the disposal of high and intermediate levels of nuclear waste often represented by HLW and ILW respectively.

identify solute and solvent in 80 solution of ethyl alcohol with water

Answers

The solute is the part of the solution that dissolves in the second component (usually a fluid). Therefore, for the mentioned solution, the solute is ehyl alcohol since it is the one dissolving in water.

As for the solvent, it is the component in which the solute dissolves. In this case, it is water.

If nickel is added to copper sulfate solution, the nickel will replace the copper. write the balanced equation

Answers

Ni(s) + CuSO₄(aq) → Cu(s) + NiSO₄(aq)

Ni + Cu²⁺ + SO₄²⁻ → Cu + Ni²⁺ + SO₄²⁻

Ni + Cu²⁺ → Cu + Ni²⁺

Answer:-

Ni + CuSO4 --> NiSO4 + Cu

Explanation:-

The symbol for Nickel is Ni.

The Symbol for copper is Cu.

Copper Sulphate has the formula CuSO4.

If Nickel replaces copper from copper sulphate then nickel sulphate is formed.

Nickel sulphate has the formula NiSO4.

So the equation becomes

Ni + CuSO4 --> NiSO4 + Cu

What is the approximate molar mass of a molecular solute if 300 g of the solute in 1000 g of water causes the solution to have a boiling point of 101°C? (Kb = 0.512°C/m; Kf = 1.86°C/m; molar mass of water = 18 g)

Answers

If i'm not mistaken, the answer would be 150 amu. 

Answer: The molar mass of solute is 156 g/mol

Explanation:

Elevation in boiling point is defined as the difference in the boiling point of solution and boiling point of pure solution.

The equation used to calculate elevation in boiling point follows:

[tex]\Delta T_b=\text{Boiling point of solution}-\text{Boiling point of pure solution}[/tex]

[tex]\Delta T_b[/tex] = ? °C

Boiling point of pure water = 100°C

Boiling point of solution = 101°C  

Putting values in above equation, we get:

[tex]\Delta T_b=(101-100)^oC=1^oC[/tex]

To calculate the elevation in boiling point, we use the equation:

[tex]\Delta T_b=iK_bm[/tex]

Or,

[tex]\Delta T_b=i\times K_b\times \frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ (in grams)}}[/tex]

where,

[tex]\Delta T_b[/tex] = 1°C

i = Vant hoff factor = 1 (For non-electrolytes)

[tex]K_b[/tex] = molal boiling point elevation constant = 0.52°C/m.g

[tex]m_{solute}[/tex] = Given mass of solute = 300 g

[tex]M_{solute}[/tex] = Molar mass of solute  = ?

[tex]W_{solvent}[/tex] = Mass of solvent (water) = 1000 g

Putting values in above equation, we get:

[tex]1^oC=1\times 0.52^oC/m\times \frac{300\times 1000}{M_{solute}\times 1000}\\\\M_{solute}=156g/mol[/tex]

Hence, the molar mass of solute is 156 g/mol

the basic organizational feature of the periodic table of elements

Answers

Atomic Number. (Or the number of protons in that element, same thing)

You are given a clear solution of KNO3. Using 3 – 4 sentences (in your own words) explain how you would determine if the solution is unsaturated, saturated or supersaturated.

Answers

Given a clear solution of KNO3, I would say that the solution is unsaturated. This type of solution has a solute concentration that is lower than the equilibrium solubility of the solute in the solvent. It is characterized by having a homogeneous solution, there would be no solid particles in the solution. Solubility is the measure of how much of a solute can be dissolved in the solution without forming any precipitate or solid particles. Any concentration above it would cause for the solute to precipitate out from the solution. To test whether the solution is unsaturated or saturated, you can add more of the KNO3 solute, if the resulting solution would still be clear then it is an unsaturated solution. However, if precipitate would appear then the original solution is saturated.

Brainliest if answered in the next 5m


A weak acid, like Hydrofluoric acid, can be dangerous if _____. Select all that apply.

concentrated
used without adult supervision
used without goggles
used without gloves
tasted

Answers

Tasted, and Used without gloves.
used without gloves. It is a dangerous and extremely powerful chemicals if touched. I hope this helped. :)

Why does a compound have characteristic properties?

Answers

A compound is a combination of elements chemically combined. Briefly explain why a beaker containing sand and water is a mixture although sand itself is a pure substance. Because it's a combination of two or more substances. ... Briefly explain why a compound has characteristic properties

Answer: Because of the arrangement of atoms in a compound.

Explanation:

A compound is defined as the chemical specie which is formed by the combination of two or more different type of atoms. For Example: [tex]H_2O,O_2[/tex] etc...

A compound has different physical and chemical properties than corresponding elements because of change in identity. For Example: Hydrogen and oxygen are gases, but the compound formed by the combination of these two that is water is liquid.

In a chemical compound, elements are combined in a fixed ratio of their masses.

Hence, a compound has characteristic property because of the arrangement of atoms in a compound

In the sun, two hydrogen nuclides react together to make an atom of helium. the process releases energy. which type of reaction is this

Answers

In the sun, two hydrogen nuclides react together to make an atom of helium. the process releases energy. This is  nuclear fusion reaction. The Sun uses this reaction to release energy and heat. Hydrogen nuclei fuse together to form helium nuclei and release energy. The formula that describes this reaction is the following:  1/1H+1/1H->3/2He

Answer:

Fusion.

Explanation:

The core squeezes together so tightly that four hydrogen nuclei combine to form one helium atom. This is the textbook definition of nuclear fusion.

A substance has a volume of 10.0 cm3 and a mass of 89 grams. What is its density?

Answers

8.9 g/cm3 since density equals mass/volume or m/v you just divide 89 by 10 to get 8.9

Answer:

Density of the substance = 8.9 g/cm³

Explanation:

The volume of the substance = 10 cm³  

Mass = 89 gm

Density = mass / volume = 89 gm / 10 cm³ = 8.9 g/cm³

 

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