The numbers represent the change in energy for a chemical reaction. They are calculated by subtracting the energy of products from the energy of reactants. Which number would result from an endothermic reaction?

Answer:

D represents the element nitrogen which will gain three valence electrons forming a 3 ion.

Answer:

answer is

Explanation:

D

Answer:

The answer is true

Explanation:

bc I took this on edgeunity

Answer:

T

Explanation:

A Spider is a creepy crawly with no vertebrae and more than 6 jointed legs.

The Spider belongs to the class Arachnida . The Spider can be referred to as a non-vertebrates hence , they don't have a vertebrae(backbone).

The Spider and Cockroach are both non-vertebrates but with different pairs of legs. A cockroach is belongs to the class Insecta in which those under this class have only six jointed legs.

The Spider has eight jointed legs which is more than six and is a characteristic of Arachnids.

A snake on the other hand is a vertebrate which exempts it from being the answer.

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Answer:

the throwing back by a body or surface of light, heat, or sound without absorbing it.

"the reflection of light"

Explanation:

i hope this helps

Answer:

D) 2( 6.02 ×10^23)

Explanation:

using n=m

M

where n = moles

m=mass of substance

M=molar mass .

n( sulfur ) =64

32

= 2

using N =nL

where N is number of entities

n = moles

L= 6.02×20^23

N( of atoms of sulfur) =2(6.02×10^23)

32(6.02 x 10²³) number of atoms are in 64 g sulfur (S) is:

C. 32(6.02 x 10²³) atoms

To determine the number of atoms in 64 grams of sulfur (S), you need to use Avogadro's number, which is approximately 6.02 x 10²³ atoms/mol. This number represents the number of atoms or molecules in one mole of a substance.

1. Find the molar mass of sulfur (S):

The molar mass of sulfur (S) is the mass of one mole of sulfur atoms, and you can find it on the periodic table. The molar mass of sulfur is approximately 32.06 g/mol.

2. Calculate the number of moles of sulfur:

To calculate the number of moles, divide the given mass (64 g) by the molar mass of sulfur (32.06 g/mol):

Number of moles = Mass of sulfur / Molar mass of sulfur

Number of moles = 64 g / 32.06 g/mol

Number of moles = 1.997 moles

3. Use Avogadro's number to find the number of atoms:

Now, multiply the number of moles by Avogadro's number:

Number of atoms = Number of moles × Avogadro's number

Number of atoms = 1.997 moles × 6.02 x 10²³ atoms/mol

Number of atoms = 1.202 x 10²⁴ atoms

So, there are approximately 1.202 x 10²⁴ atoms in 64 grams of sulfur (S). The closest option to this value is:

C. 32(6.02 x 10²³) atoms (which is equivalent to 1.924 x 10²⁴ atoms)

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Answer:

Explanation:

given mass = 697 g

molar mass = mass of H × mass of N × 3 × mass of O

= 1 × 14 × 3 × 16 = 672 g

no. of moles = given mass / molar mass = 697 / 672 = 1.03 moles

Hope this helps

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Answer:

pOH = 11

pH = 3

Explanation:

Given data:

Hydrogen ion concentration = 10⁻³ mol/L

pOH of solution = ?

pH of solution = ?

Solution:

pH = -log[H⁺]

Now we will put the values.

pH = -log[ 10⁻³]

pH = -(-3) log 10

pH = 3

pOH of solution:

pOH + pH = 14

pOH = 14 - pH

pOH = 14 - 3

pOH = 11

Answer:

[tex]\Delta S=1.8x10^{-3}\frac{kJ}{K}=1.8\frac{J}{K}[/tex]

Explanation:

Hello.

In this case, given the heat of fusion of THF to be 8.5 kJ/mol and freezing at -108.5 °C, for the required mass of 5.9 g, we can compute the entropy as:

[tex]\Delta S=\frac{n*\Delta H}{T}[/tex]

Whereas n accounts for the moles which are computed below:

[tex]n=5.9g*\frac{1mol}{72g} =0.082mol[/tex]

Thus, the entropy turns out:

[tex]\Delta S=\frac{0.0819mol*8.5 kJ/mol}{(-108.5+273.15)K}\\\\\Delta S=1.8x10^{-3}\frac{kJ}{K}=1.8\frac{J}{K}[/tex]

Best regards.

Answer:

Overall charge = -3

Explanation:

The atom of every chemical element is its smallest indivisible part. However, this atom further consists of subatomic particles namely: proton, electron, and neutron. The proton and electron are the positively charged and negatively charged particle respectively.

In a neutral atom, the amount of proton and electrons in that atom equates. However, the amount of electron and proton present in an atom determines the charge of that atom. For example, in this question, an atom is said to contain 17 protons, 17 neutrons and 20 electrons.

Since the negatively charged electrons (20) are more than the positively charged protons (17) by 3, hence, the net charge is -3.

Answer:

A high-pressure area, high, or anticyclone, is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment. Winds within high-pressure areas flow outward from the higher pressure areas near their centers towards the lower pressure areas further from their centers.

Explanation:

Answer:

15.2mL of the 0.10M sodium formate solution and 4.8mL of the 0.10M formic acid solution.

Explanation:

To find the pH of a buffer based on the concentration of the acid and conjugate base we must use Henderson-Hasselbalch equation:

pH = pKa + log [A⁻] / [HA]

Where [A⁻] could be taken as moles of the sodium formate and [HA] moles of the formic acid

4.25 = 3.75 + log [A⁻] / [HA]

0.5 = log [A⁻] / [HA]

3.162 = [A⁻] / [HA] (1)

As both solutions are 0.10M and you want to create 20mL of the buffer, the moles are:

0.10M  * 20x10⁻³L =

2x10⁻³moles = [A⁻] + [HA] (2)

Replacing (2) in (1):

3.162 = 2x10⁻³moles - [HA] / [HA]

3.162 [HA] = 2x10⁻³moles - [HA]

4.162[HA] = 2x10⁻³moles

[HA] = 4.805x10⁻⁴ moles

[A⁻] = 2x10⁻³moles - 4.805x10⁻⁴ moles = 1.5195x10⁻³moles

That means, to create the buffer you must add:

[A⁻] = 1.5195x10⁻³moles * (1L / 0.10mol) = 0.0152L =

[HA] = 4.805x10⁻⁴ moles * (1L / 0.10mol) = 0.0048L =

Answer:

1. Caffeine, C₈H₁₀N₄O₂

Amount = 1.00/194 = 0.00515 moles

2. Ethanol, C₂H₅OH

Amount = 0.0217 moles

3. Dry Ice, CO₂

amount = 0.0227 moles

Note: The question is incomplete. The compound are as follows:

1. Caffeine, C₈H₁₀N₄O₂;

2. Ethanol, C₂H₅OH;

3. Dry Ice, CO₂

Explanation:

Amount (moles) = mass in grams /molar mass in grams per mole

1. Caffeine, C₈H₁₀N₄O₂

molar mass of caffeine = 194 g/mol

Amount = 1.00 g/194 g/mol = 0.00515 moles

2. Ethanol, C₂H₅OH

molar mass of ethanol = 46 g/mol

Amount = 1.00 g/46 g/mol = 0.0217 moles

3. Dry Ice, CO₂

molar mass of dry ice = 44 g/mol

amount = 1.00 g/44 g/mol = 0.0227 moles

Answer:

Flame tests use simple equipment, making them ideal for fieldwork. Geologists use the flame test to identify the presence of metals. Forensic scientists can use flame tests at crime scenes for quick analysis of elements present. Miners use the test for analysis of samples, particularly when prospecting. Flame tests provide a good teaching tool for chemistry students learning about emission spectra.

Unlike more sophisticated spectrographic equipment, a flame test requires only a gas burner, a hydrochloric acid solution and nichrome wire to hold the sample. The process is simple: dip the nichrome wire in the acid solution and hold it in the flame to remove any impurities, then affix the sample and hold it in the flame. The emitted colors show what metal ions the sample contains. For example, Copper emits a deep blue, Sodium bright orange and Lead a grey-white color. A table of elements and their characteristic colors helps with identification.

Explanation:

Answer:

[tex]x_{CO_2}^{out} =0.25[/tex]

Explanation:

Hello.

In this case, for the reactive scheme, it is very convenient to write each species' mole balance as shown below:

[tex]CH_4:f_{CH_4}^{out}=f_{CH_4}^{in}-\epsilon \\\\O_2:f_{O_2}^{out}=f_{O_2}^{in}-2\epsilon\\\\CO_2:f_{CO_2}^{out}=\epsilon\\\\H_2O:f_{H_2O}^{out}=2\epsilon[/tex]

Whereas [tex]\epsilon[/tex] accounts for the reaction extent. However, as all the methane is consumed, from the methane balance:

[tex]0=f_{CH_4}^{in}-\epsilon \\\\\epsilon=30gmol/s[/tex]

Thus, we can compute the rest of the outlet mole flows since not all the oxygen is consumed as it is in excess:

[tex]f_{O_2}^{out}=f_{O_2}^{in}-2\epsilon=75gmol/s-2*30gmol/s=15gmol/s\\\\f_{CO_2}^{out}=15gmol/s\\\\f_{H_2O}^{out}=2*15gmol/s=30gmol/s[/tex]

It means that the mole fraction of carbon dioxide in that output is:

[tex]x_{CO_2}^{out}=\frac{15}{15+15+30} =0.25[/tex]

Best regards.

Answer:

Explanation:

It will take 3 sodium ions to neutralize 1 phosphorus ion. That's because you need 3 plus's to satisfy the - charge on phosphorous. So the chemical formula is Na3P reflecting this fact.

The answer is number 4

Answer:

B

Explanation:

Mass is defined as the quantity of matter in an object.

Answer:

height = 4.74 cm

density = 2.23 g/ cm³

Explanation:

Mass of metal = 0.650 kg (650 g)

Width = 0.136 m    

Length = 0.0451 m  

Volume of metal = 291 cm³

Height in cm = ?

density of metal =?

Solution:

Width = 0.136 m    (0.136 m×100 cm/1m = 13.6 cm)

Length = 0.0451 m  (0.0451 m×100 cm/1m = 4.51 cm)

First of all we will calculate the height:

Volume = height× width× length

291 cm³ =      h     × 13.6 cm × 4.51 cm

291 cm³ =      h     × 61.34 cm²

h = 291 cm³ / 61.34 cm²

h = 4.74 cm

Density:

d = m/v

d = 650 g/291 cm³

d = 2.23 g/ cm³

Answer:..

Explanation:

Answer:

The frequency is  [tex]f =  2,01 * 10^{15} \  Hz  [/tex]

Explanation:

From the question we are told that

   The energy required to ionize boron is [tex]E_b  =  801 KJ/mol[/tex]

Generally the ionization energy of boron pre atom is mathematically represented as

     [tex]E_a  =  \frac{E_b}{N_A}[/tex]

Here  [tex]N_A[/tex] is the Avogadro's constant with value [tex]N_A  =  6.022*10^{23}[/tex]

So

      [tex]E_a  =  \frac{801}{6.022*10^{23}}[/tex]

=>     [tex]E_a  =  1.330 *10^{-18} \  J/atom [/tex]

Generally the energy required to liberate one electron from an atom is equivalent to the ionization energy per atom and this mathematically represented as

       [tex]E =  hf  =  E_a[/tex]

=>     [tex]  hf  =  E_a[/tex]

Here h is the Planks constant with value [tex]h = 6.626 *10^{-34}[/tex]

So

       [tex]f =  \frac{1.330 *10^{-18}}{ 6.626 *10^{-34}}[/tex]

=>      [tex]f =  2,01 * 10^{15} \  Hz  [/tex]

Answer:

mass = 508 g

Explanation:

Given data:

Number of moles of Cu = 8 mol

Mass in gram = ?

Solution:

Number of moles = mass/molar mass

Molar mass of Cu is 63.5 g/mol.

Now we will put the values in formula.

8 mol = mass /63.5 g/mol

mass = 63.5 g/mol ×8 mol

mass = 508 g

Answer:

[tex]p_2=5.17torr[/tex]

Explanation:

Hello.

In this case, by using the Clausius-Clapeyron Equation which allows us to relate the vapor pressure, temperature and heat of vaporization as shown below:

[tex]ln(\frac{p_1}{p_2} )=\frac{\Delta _vH}{R}(\frac{1}{T_2}-\frac{1}{T_1} )[/tex]

Whereas [tex]p_1[/tex] is 760 torr due to the normal conditions. In such a way, for computing the vapor pressure of benzaldehyde at 53.5 °C (326.65 K), we proceed as shown below:

[tex]\frac{p_1}{p_2} =exp[\frac{48800J/mol}{8.314\frac{J}{mol*K}}(\frac{1}{326.65K}-\frac{1}{451.0K} )]\\\\\frac{p_1}{p_2}=147.0[/tex]

Thus, the vapor pressure at the final T is:

[tex]p_2=\frac{p_1}{147.0}=\frac{760torr}{147.0}\\ \\p_2=5.17torr[/tex]

Best regards!

Answer:

Solar Cell

Explanation:

Claim 1: The sun (solar cells) is the best energy source for the rescue team.

Answer:

Neon

Explanation:

All noble gases have 8 valence electrons except helium.

Noble gases include Helium, neon, argon, krypton, xenon, redon.

Electronic configuration of neon:

Ne₁₀ = [He] 2s² 2p⁶

All other options are incorrect because,

Electronic configuration of Fluorine:

F₉ = [He] 2s² 2p⁵

Fluorine have seven valence electrons.

Electronic configuration of oxygen:

O₈ = [He] 2s² 2p⁴

Oxygen have six valence electrons.

Electronic configuration of sodium:

Na₁₁ = [Ne] 3s¹

sodium have one valence electron.

The physical changes are:

The chemical changes are:

Matter can undergo 2 kinds of changes:

Let's consider the following text.

When my alarm went off at 70'clock, I hit snooze" a few times then finally got out of bed with excitement for my morning bowl of cereal. I poured the cereal and milk into my bowl. But before I even drank it, I could tell from the smell that the milk had soured! So, I decided to blend up a banana smoothie instead. I took some ice out of the freezer and grabbed the only banana that we had in the kitchen, which was covered in brown spots. My grumbling stomach needed to be satisfied before school so I didn't really care.

Just as I was sitting down to drink my smoothie my little brother came bounding into the kitchen and asked, Would you make some eggs and toast for me for breakfast?

"Ugh, sure," I said. I cut a piece of bread in half and put it in the toaster, then I cracked two eggs and whipped them with a fork. I reached for one of my mother's copper cooking pans in the cabinet and saw that it was completely tarnished! I didn't want to be blamed for this, so I ran to tell my mother right away. As I ran out of the kitchen slipped on that banana peel and it smeared all over the floor. As I lay on the floor with the wind knocked from me, I noticed that our family's plants were dying and that some water had evaporated from our fish tank. I made a mental note to take care of these things after school.

Just as I regained my breath and stood up, I heard glass breaking upstairs and my mother shrieking. I ran up the stairs, breathing heavily now. Steam was rolling out from the open bathroom door. When the steam cleared, saw why my mother had been screaming. Before me was my older sister standing in the bathroom with purple hair. I inferred from the scene that my mother had dropped a glass when she first saw her look what your sister did to her hair my mother yelled furiously I decided that I needed to get out of the house immediately, this morning was a crazy one!

A distinct smell was waiting up the stairway and I realized that my brother's toast must be burning! When reached the kitchen, my brother was happily spreading butter on his very browned toast. "I like my toast really crispy!" he said.

"Good I can't handle any more chaos this morning! I exclaimed. I grabbed my backpack headed out into the foggy morning air, and hopped on my slightly rusted bicycle to ride to school. A few minutes into my ride, my stomach grumbled and I realized that I never got a chance to drink my banana smoothie. Luckily, I had stashed a chocolate bar in my backpack yesterday. "Yes! I thought as I stopped pedaling, grabbed the chocolate and broke off a piece. As the chocolate melted in my mouth, I knew that my day was bound to get better!

The physical changes are:

The chemical changes are:

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Answer:

pH = 9.26

Explanation:

Let's make the reaction of this weak base:

C₅H₅N  +  H₂O  ⇄    C₅H₅NH⁺  +  OH⁻     Kb

We do not know the Kb, but we can discover it from pKb

Kb = 10^⁻pKb  →  10⁻⁸'⁷⁷ = 1.70×10⁻⁹

So, let's make the expression for Kb

Kb = [OH⁻] . [C₅H₅NH⁺] / [C₅H₅N]

In the equilibrum, we would have  0.20 moles from the begining - x (react)

So we would proudce x moles of OH⁻ and x moles of C₅H₅NH⁺.

In conclussion:

1.70×10⁻⁹ = x . x / (0.20 - x)

To avoid the quadratic formula we can miss the x from the substraction

1.70×10⁻⁹ = x² / 0.20

1.70×10⁻⁹ . 0.20 = x²

We avoid the x from the (0.20-x), because the base is so concentrated, and Kb is very small.

x = √(1.70×10⁻⁹ . 0.20) → 1.84×10⁻⁵

That's the value of [OH⁻], so we can calculate pOH

- log [OH⁻] = pOH → - log 1.84×10⁻⁵ = 4.73

Then pH = 14 - pOH

14 - 4.73 = 9.26

The pH of a 0.20 M aqueous solution of pyridine is approximately 9.26.

Given,

pKb = 8.77

Concentration = 0.20M

The pKb is related to the pKa by the equation: pKa + pKb = 14.

pKa = 14 - 8.77 = 5.23.

Since pyridine is a base, it can be treated as the conjugate base of its corresponding acid. The acid is the pyridinium cation, which is formed by the protonation of pyridine.

Now, the equilibrium between the pyridine (base) and the pyridinium ion (acid):

C₅H₅N + H₂O ⇌ C₅H₅NH⁺ + OH⁻

The equilibrium constant expression for this reaction can be expressed as:

Kb = [tex]\frac{([C_5H_5NH^+][OH^-])}{[C_5H_5N]}[/tex]

At equilibrium, the concentration of OH⁻ will be equal to the concentration of [C₅H₅NH⁺], as pyridine is a weak base and will not significantly dissociate in water.

Kb = [tex]\frac{[OH^-]^2}{[C_5H_5N]}[/tex]

Kb = [tex]10^{(-8.77)[/tex]

Kb = [tex]\frac{[OH^-]^2}{[C_5H_5N]}[/tex]

[tex]10^{(-8.77)[/tex] = [tex]\frac{[OH^-]^2}{(0.20 M)}[/tex]

[OH⁻]² = [tex]10^{(-8.77)[/tex] ₓ 0.20 M

[OH⁻] = [tex]\sqrt{10^{-8.77} \times 0.20M}[/tex]

[OH⁻] ≈ 1.42 x 10⁻⁵ M.

The pOH (the negative logarithm of the hydroxide ion concentration):

pOH = [tex]-log_{10}([OH^-])[/tex]

pOH = [tex]-log_{10}[/tex](1.42 x 10⁻⁵)

pOH ≈ 4.85

Since pH + pOH = 14, the pH:

pH = 14 - pOH

pH = 14 - 4.85

pH ≈ 9.26

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Answer:

Covalent bonds

Explanation:

i'm pretty sure it's fusion but i may be wrong.

Answer:

19.3 g/cm3

Explanation:

A 10.0 cm3 sample of copper has a mass of 89.6 g. What is the density of copper? 19.3 g/cm3.

Answer:

0 degree C

Explanation:

0 degree C = 32 degree F

0 degree F = -17.7778 degree C

Answer:

0 degrees C would be warmer

Explanation: