A burning match releases 838.2 J of energy. Convert the energy released by 20 matches to the following energy units: (provide an answer in 4 significant figures)
________ Kilojoules
________ Calories
________ Food Calories
________ calories
________ kcal

Answer: 1 mole per L

Explanation:

(2M)(500mL)=(M)(1000mL)

1000=(M)(1000mL)

M=1

Taking into account the definition of dilution, if 500 mL of 2.0 M HCl is diluted with water to a volume of 1 liter, the molarity of the new solution is 1 M.

When it is desired to prepare a less concentrated solution from a more concentrated one, it is called dilution.

Dilution is the process of reducing the concentration of solute in solution, which is accomplished by simply adding more solvent to the solution at the same amount of solute.

In a dilution the amount of solute does not change, but as more solvent is added, the concentration of the solute decreases, as the volume (and weight) of the solution increases.

A dilution is mathematically expressed as:

where

In this case, you know:

Replacing in the definition of dilution:

2.0 M× 500 mL= Cf× 1000 mL

Solving:

(2.0 M× 500 mL)÷ 1000 mL= Cf

1 M= Cf

In summary, if 500 mL of 2.0 M HCl is diluted with water to a volume of 1 liter, the molarity of the new solution is 1 M.

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Answer:

1.30atm

Explanation:

P1/T1 = P2/T2

1.07/393 = P2/478

Answer: the first one is correct

Explanation:

jhkfjfjgjgjjggj

Answer:

d

Explanation:

Answer:

The metal with the lowest specific heat capacity

Explanation:

Hello, this question can be solved when we compare their specific heat capacities.

Specific heat capacity of a metal /substance is the heat required to raise it's temperature by one degree Celsius.

Mathematically,

Q = mc∇θ

Q = heat energy applied

M = mass of the metal

C = specific heat capacity of the metal

∇θ = (θ₂ - θ₁) which corresponds to the change in temperature of the metal.

In a given experiment of different metals with different specific heat capacities, assuming they're of equal mass and same amount of energy is applied with the same amount of initial temperature, the metal with the lowest specific heat capacity would have the highest final temperature likewise the metal with the highest specific heat capacity would have the lowest final temperature.

The is due to the energy required to raise the temperature of the metal by 1°C

Answer:

B) It must be a weak acid.

Explanation:

If HA is a strong acid

[tex]HA\rightleftharpoons H^++A^-[/tex]

Now the pH value can be written as follows

[tex]pH=-log[H^+]\\pH=-log(5\times 10^{-2})\\pH=2\times log5\\pH=1.4[/tex]

But given that acid HA has 2.3 pH value.

Therefore we can say that HA is weak acid.

Thus the answer will be option (B).

B) It must be a weak acid.

Answer:

[tex]T=1235K=962\°C[/tex]

Explanation:

Hello,

In this case, from thermodynamics, it is widely known that the entropy of fusion is defined in terms of the enthalpy of fusion at the fusion temperature (melting point) as shown below:

[tex]\Delta _fS=\frac{\Delta _fH}{T}[/tex]

Thus, solving for the melting point:

[tex]T=\frac{\Delta _fH}{\Delta _fS}[/tex]

Hence, for silver:

[tex]T=\frac{11.30kJ/(mol)*\frac{1000J}{1kJ} }{9.150J/(mol*K)} \\\\T=1235K=962\°C[/tex]

Which is a typical high temperature for a metal such as silver.

Best regards.

Answer: The [tex][OH^-][/tex] of a solution is [tex]10^{-12}[/tex] M

Explanation:

Molarity of a solution is defined as the number of moles of solute dissolved per liter of the solution.

[tex]Molarity=\frac{n\times 1000}{V_s}[/tex]

where,

n = moles of solute

[tex]V_s[/tex] = volume of solution in ml

moles of [tex]HCl[/tex] = [tex]\frac{\text {given mass}}{\text {Molar mass}}=\frac{0.0912g}{36.5g/mol}=0.0025mol[/tex]

Now put all the given values in the formula of molality, we get

[tex]Molarity=\frac{0.0025\times 1000}{250}=0.01[/tex]

pH or pOH is the measure of acidity or alkalinity of a solution.

[tex]HCl\rightarrow H^++Cl^{-}[/tex]

According to stoichiometry,

1 mole of [tex]HCl[/tex] gives 1 mole of [tex]H^+[/tex]

Thus [tex]0.01[/tex] moles of [tex]HCl[/tex] gives =[tex]\frac{1}{1}\times 0.01=0.01[/tex] moles of [tex]H^+[/tex]

Putting in the values:

[tex][H^+][OH^-]=10^{-14}[/tex]

[tex][0.01][OH^-]=10^{-14}[/tex]

[tex][OH^-]=10^{-12}[/tex]

Thus the [tex][OH^-][/tex] of a solution prepared by dissolving 0.0912 g of hydrogen chloride in sufficient pure water to prepare 250.0 ml of solution is [tex]10^{-12}[/tex] M

The  [OH-] of a solution is [tex]10^{12}[/tex] M.

Molarity of a solution is defined as the number of moles of solute dissolved per liter of the solution.

M = n/ V..................(1)

where,

n = moles of solute

V = volume of solution in ml

Calculation for number of moles:

Moles of HCl =  0.0912 g/ 36.5 g/mol = 0.0025 mol

On substituting the values in equation 1:

M = n/ V

M= 0.0025*1000 / 250

M=0.01 M

pH or pOH is the measure of acidity or alkalinity of a solution.

[tex]HCl---- > H^++Cl^-[/tex]

According to stoichiometry,

1 mole of HCl  gives 1 mole of [tex]H^+[/tex]

Thus, 0.01 moles of HCl gives =  1 / 1 *0.01 = 0.01 mole of [tex]H^+[/tex]

On adding the values:

[tex][H^+][OH^-]=10^{14}\\\\(0.01)[OH^-]=10^{-14}\\\\OH^-=10^{-12}[/tex]

Thus, the [OH-]  of a solution prepared by dissolving 0.0912 g of hydrogen chloride in sufficient pure water to prepare 250.0 ml of solution is [tex]10^{-12}[/tex]  M.

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Answer:

677.7 mmHg

Explanation:

The first empirical study on the behaviour of a mixture of gases was carried out by John Dalton. He established the effects of mixing gases at different pressures in the same vessel.

Dalton's law states that,the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the individual gases present in the mixture of gases. When a gas is collected over water, the gas also contains some water vapour. The partial pressure of the gas will now be given as; total pressure of gas mixture - saturated vapour pressure of water (SVP) at that temperature.

Given that;

Total pressure of gas mixture = 692.2 mmHg

SVP of water at 17°C = 14.5 mmHg

Therefore, partial pressure of oxygen = 692.2-14.5

Partial pressure of oxygen = 677.7 mmHg

Answer:

Number of moles = 0.1058 mol

Explanation:

Density = 1.08 g/mL

Volume = 10ml

Density = Mass / Volume

Mass = Density * Volume

Mass = 1.08 * 10 = 10.8g

The molar mass of acetic anhydride = 102.09 g/mol

Molar mass = Mass / Moles

Upon solving for moles;

Moles = Mass / Molar mass

Moles = 10.8 / 102.09 = 0.1058 mol

The moles of acetic acid used in the experiment has been 0.1058 mol.

Density has been defined as mass of a substance per unit volume. The density has been expressed as:

[tex]\rm Density=\dfrac{Mass}{Volume} [/tex]

The moles have been the mass of the substance with respect to the molar mass. The moles of a substance has been given as:

[tex]\rm Moles=\dfrac{Mass}{Molar\;mass} [/tex]

The given sample of acetic acid has density = 1.08 g/ml

The volume of the sample used in the experiment has been 10 ml.

Substituting the values for the mass of acetic acid:

[tex]\rm 1.08=\dfrac{Mass}{10}\\ Mass=1.08\;\times\;10\;g\\ Mass=10.8\;g[/tex]

The mass of the acetic acid used has been 10.8 g.

The molar mass of acetic acid has been 102.09 g/mol.

Substituting the values for the moles of acetic acid:

[tex]\rm Moles=\dfrac{10.8}{102.09} \\ Moles=0.1058\;mol[/tex]

The moles of acetic acid used in the experiment has been 0.1058 mol.

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Answer: 18.8 g

Explanation:

To find the mass of a 23.8 mL sample, all we have to do is set up a proportion.

[tex]\frac{0.791g}{mL} =\frac{x}{23.8mL}[/tex]

[tex]18.8358=x[/tex]

x=18.8 g

We round to 18.8 because of significant figures.

Taking into account the definition of density, the mass of a 23.8 mL sample of methanol is 18.83 g.

But first you must know that density is defined as the property that matter, whether solid, liquid or gas, has to compress into a given space.

Then, density is a quantity that allows us to measure the amount of mass in a certain volume of a substance. That is, it is the relationship between the weight (mass) of a substance and the volume it occupies.

Then, the expression for the calculation of density is the quotient between the mass of a body and the volume it occupies:

[tex]density= \frac{mass}{volume}[/tex]

In this case:

Replacing in the definition of density:

[tex]0.791 \frac{g}{mL} = \frac{mass}{23.8 mL}[/tex]

Solving:

mass= 0.791 [tex]\frac{g}{mL}[/tex]× 23.8 mL

mass= 18.83 g

In conclusion, the mass of a 23.8 mL sample of methanol is 18.83 g.

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Answer:

Both oxygen atoms have zero partial charge.

Explanation:

In covalent bonds, electrons are shared between the two bonding atoms. The shared electron pair of the covalent bond is positioned between the nuclei of the two bonding atoms.

A covalent bond may be formed between two or more elements of different electronegativities. When a difference in electro negativity exists between these atoms in a covalent bond, the molecule becomes polarized. The shared electron pair of the covalent bond becomes closer to the nucleus of the more electronegative atom (s). This more electronegative atom (s) becomes partially negative while the other atom becomes partially positive.

When the two bonding atoms are of equal electronegativities such that the electro negativity difference between the bonding atoms is zero, there is now no difference in electro negativity and no consequent partial charges.

Since the two oxygen atoms have the same electro negativity, there is no difference in electronegativity, hence there is no partial charge between the two oxygen atoms.

Answer:

Both oxygen atoms have zero partial charge.

Explanation:

Answer:

Option D is correct.

n = 6 to n = 2

Explanation:

Like all waves emitted from the movement of electrons from one energy level to another, the wavelength (λ) is given by the equation involving Rydberg's constant

(1/λ) = Rₕ [(1/n₂²) - (1/n₁²)]

where Rₕ = 10973731.57 m⁻¹ = (1.0974 × 10⁷) m⁻¹

n₂ = principal quantum number corresponding to the final energy level of the electron = 2 (For Balmer Series)

n₁ = principal quantum number corresponding to the final energy level of the electron = ?

λ = 410 nm = (410 × 10⁻⁹) m

(1/λ) = (2.439 × 10⁶) m⁻¹

2.439 × 10⁶ = (1.0974 × 10⁷) [(1/2²) - (1/n₁²)]

0.25 - (1/n₁²) = (2.439 × 10⁶) ÷ (1.0974 × 10⁷) = 0.2222602562

(1/n₁²) = 0.25 - 0.2222602562 = 0.0277397438

n₁² = (1/0.0277397438) = 36.05

n₁ = 6

Hope this Helps!!!

Answer:

Molarity

Explanation:

The conversion of g/mol to g/L molarity can be used. Thus, option C is correct.

The g/mol has been the amount of solute present in a mole. The g/mol has been the molecular weight of the compound.

The g/L has been the mass of solute present in a L of solution. The g/L has  the unit for density.

Molarity has been the moles of solute present in the liter of solution. It has been given as mol/L.

The product of g/mol and g/L gives the value of mol/L. Thus, to convert g/mol to g/L molarity can be used. Thus, option C is correct.

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Answer:

Heating the mixture to a temperature above the boiling point of acetic acid, but below 100°C (the boiling point of water). The vapours from the acetic acid rise, and go into a tube. They are then condensed within the tube, and run off into a separate storage area. Because water can exist as a gas at pretty much any temperature above 0°C, it will result in an impure mixture, but repeatedly doing this will get the acetic acid to the desired purity.

Answer:

193.07 g / mol

Explanation:

Molar mass of (NH₄)₃ = 3 * (14.01 + 4 * 1.01) = 54.15

As = 74.92 and O₄ = 4 * 16 = 64

Answer is 54.15 + 74.92 + 64 = 193.07

Answer:

"The active site of the enzyme has a complementary rigid structure" belongs to the key and lock system

"The conformation of the enzyme changes when it binds to the substrate so that the active site conforms to the substrate." belongs to the induced fit system.

"The substrate binds to the enzyme at the active site, forming an enzyme-substrate complex" belongs to both, that is, the key and lock system and the induced fit system.

"The substrate binds to the enzyme through non-covalent interactions" can belong to both enzyme systems.

Explanation:

Enzymatic key and lock systems bear this name because the enzyme at its site of union with the substrate has an ideal shape so that its fit is perfect, similar to a headbreaker, so once they are joined they are not It can bind another substrate to the enzyme, since they are generally associated with strong chemical bonds.

The shape of the enzyme's active site is a negative of what the shape of the substrate would be.

On the other hand, in the mechanism or enzyme system of induced adjustment, the enzyme has an active site that is where it binds with the substrate and another site where another chemical component binds, which when this chemical component binds this enzyme changes its morphology and becomes "active" to bond with your substrate.

This happens a lot in the inactive enzymes that are usually activated in digestive processes since the fact that these enzymes are constantly active would be dangerous, therefore the body takes the induced enzyme system as a control mechanism, where a molecule or chemical compound induces change morphological of an enzyme by means of the allosteric union so that it joins its substrate and catalyzes or analyzes it, depending on the enzymatic character of the enzyme.

Answer:

a lower temperature to liquefy

Explanation:

Answer:

[tex]Pb(CO_{3})_{2} \\Pb(NO_{3})_{4} \\FeCO_{3}\\Fe(NO_{3})_{2}[/tex]

Explanation:

[tex]Pb^{4+}(CO_{3}^{2-})_{2} --->Pb(CO_{3})_{2} \\Pb^{4+} (NO_{3}^{-})_{4} --->Pb(NO_{3})_{4} \\Fe^{2+} CO_{3}^{2-} --->FeCO_{3}\\Fe^{2+} (NO_{3}^{-})_{2}--->Fe(NO_{3})_{2}[/tex]

Answer:

42.64 M

Explanation:

Step 1: Given data

Step 2: Convert the volume of the solution to liters

We will use the relationship 1 L = 1,000 mL.

[tex]189.98 mL \times \frac{1L}{1,000mL} = 0.18998L[/tex]

Step 3: Calculate the molarity of the solution

The molarity is equal to the moles of solute divided by the liters of solution.

[tex]M= \frac{8.1mol}{0.18998L} = 42.64 M[/tex]

Answer:

If gold has a rare, high density then it would sink quickly. If mixed substances that are less-valued, are added to the gold crown (remember that gold is rare and very dense which makes it special) then we can assume the cheap substances are less dense, thus making the crown FLOAT more rather than sink (I say more, because unless the crown was extremely mixed with cheap material then it could possibly float but it depends on how much is in the crown). Summary: The crown would either be lighter and float, or barely be sunken due to the less-dense substance.

*Hint to think about: People consider cheaper things lighter such as plastic ring/less dense  for example, compared to a silver ring which is heavier/more dense (btw heavy does not always mean high density, it depends on the liquid density )

Hope this actually helps!

Explanation:

High-Desnity=Sink

Low Density=Float

Answer:

I would put A

Explanation:

A new substance is produced as a result of a chemical reaction in which bonds between the molecules of the reactant and product are broken and new bonds are formed. Here the products are Al₂O₃ and Fe. The correct option is A.

Chemical reactions are interactions between two or more molecules that result in the production of new products. Products, as opposed to reactants, are compounds that result from an interaction between two other substances.

The reactants are on the left, while the products that are created are on the right. A one-headed or two-headed arrow connects the reactants and products.

Thus the correct option is A.

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Explanation:

[tex]=\dfrac{1.0505\times 10^{23}}{6.022\times 10^{23}}\times 44\\\\=7.675\ \text{grams}[/tex]

Answer:

0.623 M

Explanation:

Step 1: Given data

Step 2: Calculate the percent by volume (%m/v)

We will use the following expression.

[tex]\%m/v = \%m/m \times \rho = 7.00\% \times 1.071g/mL = 7.50g\%mL[/tex]

Step 3: Calculate the molarity

7.50 g of magnesium sulfate are dissolved in 100 mL of the solution. The molarity is:

[tex]M = \frac{7.50g}{120.37g/mol \times 0.100L } = 0.623 M[/tex]

Answer:

Exothermic interractive are the following: NaOH, KOH, CaCl₂

Endothermic interactive are the following: NaCl, NH₄NO₃, NaNO₃

Explanation:

NaOH, KOH, and CaCl2 are exothermic reactants. NaCl, NH4NO3, and NaNO3 are endothermic interacting substances.

Chemical processes that can release or absorb energy are referred to as endothermic. In endothermic reactions, more energy is used when bonds in the reactants are broken than is released when new bonds are formed in the products.

When the temperature of the an isolated system drops while the surroundings of the a non-isolated system warm up, this is known as an endothermic response. The heat of reaction is generally positive in endothermic processes (qrxn>0).

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Answer:

33.3% of Sn in the sample

Explanation:

The addition of SO₄⁻ ions produce the selective precipitation of Pb²⁺ to produce PbSO₄.

Moles of PbSO₄ (molar mass 303.26g/mol) in 2.93g are:

2.93g ₓ (1mol / 303.26) = 9.66x10⁻³ moles PbSO₄ = Moles Pb²⁺.

As molar mass of Pb is 207.2g/mol, mass in 9.66x10⁻³ moles of Pb²⁺ is:

9.66x10⁻³ moles of Pb²⁺ ₓ (207.2g / mol) = 2.00g of Pb²⁺

As mass of the sample is 3.00g, mass of Sn²⁺ is 3.00g - 2.00g = 1.00g

And the percentage of Sn in the sample is:

1.00g / 3.00g ₓ 100 =

Combining quantum theory with wave motion of atomic particles is: Wave Mechanics

Answer:

Wavelength, λ  = 6.7 x 10^-11 m

Explanation:

Frequency and wavelength are inversely proportional to each other.

In this problem;

f =  4.5 x 10^18 Hz

wavelength, λ = ?

Speed of light, c = 3 x 108 m/s.

These variables are related by the following equation;

c = λ * f

Making λ subject of focus, we have;

λ = c / f

λ = 3 x 10^8 / 4.5 x 10^18

λ  = 0.67 x 10^-10

λ  = 6.7 x 10^-11 m

Answer:

The correct answer is 1.17 moles

Explanation:

The ideal gas equation combines the pressure (P), volume (V), temperature (T) and number of moles of a gas (n):

PV= nRT

R is the gas constant (0.082 L.atm/K.mol)

In this case, we have:

V= 7.2 L

P= 4.0 atm

T= 27ºC + 273 = 300 K

We calculate the number of moles (n) of gas as follows:

n= (PV)/(RT)= (4.0 atm x 7.2 L)/(0.082 L.atm/K.mol x 300 K) = 1.17 mol

Answer:

A, B and C are compounds

Explanation:

First of all, I need to establish that when carbon is burnt in excess oxygen, carbon dioxide is obtained as shown by this equation; C(s) + O2(g) ----> CO2(g).

Looking at the presentation in the question, A was said to be heated strongly and it decomposed to B and C. Only a compound can decompose when heated. Elements can not decompose on heating. Secondly, compounds usually decompose to give the same compounds that combined to form them. Compounds hardly decompose into their constituent elements.

Again from the information provided, the compound A is a white solid. This is likely to be CaCO3. It decomposes to give another white solid. This may be CaO and the gas was identified as CO2.

Hence;

CaCO3(s)--------> CaO(s) + CO2(g)

Answer:

Sn and Ge

Explanation:

To obtain the more metallic element, we compare the group in which both elements are. Generally the element with the lower ionzation energy is he more metallic one.

Ionization energy increases fro left to right across a period. Ionization energy decreases down the group.

1. When comparing the two elements A s and S n , the more metallic element is ______based on periodic trends alone.

Sn has a lower ionization energy so it is the more metallic one.

2. When comparing the two elements G e and S b , the more metallic element is ________ based on periodic trends alone.

Ge has a lower ionizaiton energy compared to Sb. So it is more metallic element than Sb.