The concentration of Fe2 in a sample is determined by measuring the absorbance of its complex with ferroxine. The sample, measured in a 1.00 cm cuvette, has an absorbance of 0.242 . The reagent blank in the same cuvette has an absorbance of 0.041. What would be the absorbance reading for each of these two solutions if measured in a 5.00 cm cuvette

Answer:

We know that the specific heat of water is:

c = 1cal/g*°C

This means, that we need 1 cal to increase the temperature of 1 gram of water by 1°C

Here, we increased the temperature of 50.1g of water by 12°C

Then the number of calories needed to do this is given by:

x = (mass of water in grams)*(how much increased the temp in °C)*1cal/g*°C

x = (50.1g*12°C)*1cal/g*°C = 601.2 cal

But we want this in Kcal, remember that:

1Kcal = 1000cal

Then:

601.2 cal = (601.2/1000) Kcal = 0.6012 Kcal

Now, for the cracker part, the energy was released by the amount of cracker that was burned.

The original mass was 2.4g

the final mass ios 1.3g

the difference is:

2.4g - 1.3g = 1.1g

This means that 1.1g was the burned mass.

The number of kilocalories of heat per gram released by the cracker is just:

n = (0.6012 Kcal)/(1.1 g) = 0.547 Kcal/g

0.547 kilocalories per gram.

Answer:

41 g

Explanation:

The equation of the reaction is;

Cr(NO3)3(aq)+Na3PO4(aq)=3NaNO3(s)+CrPO4(aq)

Number of moles of chromium nitrate = 37g/ 146.97 g/mol = 0.25 moles

1 mole of sodium phosphate reacts with 1 mole of chromium nitrate

x moles of sodium phosphate react as with 0.25 moles of chromium nitrate

x= 1 × 0.25/1

x= 0.25 moles

Mass of sodium phosphate = 0.25 moles × 163.94 g/mol

Mass of sodium phosphate = 41 g

endothermic absorbs heat

exothermic gives heat

a. endothermic

b. exothermic

c. endothermic

d. exothermic

a. Ice melting - endothermic

b. Water condensing on the surface - exothermic

c. Baking a cake - endothermic

d. The chemical reaction inside an instant cold pack - endothermic

e. A car using gasoline - exothermic

An exothermic reaction can be described as a thermodynamic chemical reaction that emits energy from the system to its surroundings usually in the form of light, heat, or sound.

While an endothermic reaction can be described as an opposite of an exothermic reaction where the energy gains in the form of heat. In exothermic chemical reactions, the bond energy is transformed into thermal energy.

In exothermic reactions, the reaction happens the form of the kinetic energy of molecules when the energy is released. The release of energy is due to the electronic transition of electrons from one energy level to another.

The burning of gasoline, and water condensation is also an exothermic reaction in which energy is released while ice melting and baking cake is an endothermic reaction.

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Answer: Chemicals like acids and bases are harmful and must be neutralized before draining.

Explanation:

A strong acid or strong base is required to be diluted or neutralized before it is discarded in the drain as if is discarded without diluting and neutralization it can spill and splash from sink or drain and can harm people in chemistry lab, moreover the fumes of the discarded chemical on spilling can cause respiratory tract burning and can even cause fire hazard so it must be converted into less harmful form and then must be drained.  

Answer:

(A) Slipping and breaking

(B) Clean and dry

(C) Cracks

Explanation:

This describes the process of unpacking a glassware for use.

You should set out support like a cork ring or clamp (these are simple machines that'll hold the glassware in place) before removing the glassware from a glassware kit; to place the glassware in and to stop it from slipping and breaking.

Thoroughly check that the glassware is clean and dry and that it does not have any cracks, before using it.

Answer:

1. Participating in calcium homeostatis storage of calcium.

2. High capacity calcium (Ca) regulation and protection against herbivory

[tex]\large \boxed{\sf 2 \: functions \: of \: crystals \: are :- } [/tex]

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[tex] \sf \: \underline{ Calcium \: oxalate \: (CaOx) \: crystals} \: are \: distributed \: \\\sf among \: all \: taxonomic \: levels \\ \sf\: of \: photosynthetic \: organisms \: from \\ \sf \: small \: algae \: to \: angiosperms \: and \: giant \: gymnosperms .[/tex]

__________________

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[tex]\sf Bone \: is \: mostly \: made \: of \: \underline{mineral \: crystals} \: \\ \sf and \: the \: protein \: collagen. \: The \: mineral  \: crystals \: bone  \\ \sf\: provide \: strength \: and \: rigidity \: for \: the \: matrix \: upon \: \\ \sf \: and \: within \: which \: they \: are \: deposited.[/tex]

Explanation:

Given set of elements in one column and their classification in another column.

1. Phosporus                         c.Metallic lattice

2. Bromine                           d.Covalent network.

3. Hydrogen                          b. Molecules

4. Krypton                              a. Discrete atoms

Since Krypton is an inert gas and it exists in discrete atoms.

Hydrogen exists as a diatomic gas.

Bromine exists as Br_2 liquid and is held by covalent bonds.

Phosphorus exists as P_4 molecules and it exits as a metallic lattice.

Answer:

See explanation

Explanation:

The molecule IF5 possesses five I-F polar bonds. However, the presence of polar bonds does not automatically imply that the molecule will be polar.

The geometry of the molecule is very important in determining the polarity of a compound. Since IF5 has a lone pair of electrons, the molecule is bent and as such there is a permanent dipole moment created in the molecule thereby making IF5 polar in nature.

Explanation:

The volume of given lead nitrate solution is:

52.5 mL.

The amount of lead iodide formed is ---0.248 g.

To get the molarity of lead (II) ion follow the below-shown procedure:

The number of moles of lead iodide formed is:

[tex]number of moles of lead iodide(n)=mass of lead iodide/its molecular mass\\n=0.248 g/461.01g/mol\\n=0.000537mol[/tex]

0.000537 mole of lead iodide contains --- 0.000537 moles of lead (II) ion.

Thus, the number of moles are there, volume is there, and to get the molarity of lead (II) ion use the formula:

[tex]Molarity=\frac{number of moles}{volume in L.} \\M=0.000537 mol / 0.0525 L.\\M=0.0102mol/L[/tex]

Molarity of lead iodide is --- 0.0102 M.

Answer: The volume of dinitrogen difluoride gas collected is 13.31 L.

Explanation:

Given: Temperature = [tex]5.0^{o}C[/tex] = (5 + 273) K = 278 K

Moles = 583 mmol (1 mmol = 0.001 mol) = 0.583 mol

Pressure = 1 atm

Formula used to calculate volume is as follows.

PV = nRT

where,

P = pressure

V = volume

n = no. of moles

R = gas constant  = 0.0821 L atm/mol K

T = temperature

Substitute the values into above formula as follows.

[tex]PV = nRT\\1 atm \times V = 0.583 \times 0.0821 L atm/mol K \times 278 K\\V = 13.31 L[/tex]

Thus, we can conclude that the volume of dinitrogen difluoride gas collected is 13.31 L.

Answer:

Explanation:

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Answer :  The work done for path A and path B is -685.3 J and -478.1 J  respectively.

Explanation :

To calculate the work done for path A :

First we have to calculate the moles of the gas.

where,

= initial pressure of gas  = 2.57 atm

= initial volume of gas  = 3.42 L

n = moles of gas  = ?

R = gas constant = 0.0821 atm.L/mol.K

T = temperature of gas  = 298 K

Now put all the given values in the above formula, we get:

According to the question, this is the case of isothermal reversible expansion of gas.

As per first law of thermodynamic,

where,

= internal energy

q = heat

w = work done

As we know that, the term internal energy is the depend on the temperature and the process is isothermal that means at constant temperature.

So, at constant temperature the internal energy is equal to zero.

The expression used for work done will be,

where,

w = work done on the system = ?

n = number of moles of gas  = 0.359 mole

R = gas constant = 8.314 J/mole K

T = temperature of gas  = 298 K

= initial volume of gas  = 3.42 L

= final volume of gas  = 7.39 L

Now put all the given values in the above formula, we get :

Thus, the work done of path A is, -685.3 J

To calculate the work done for path B :

The formula used for isothermally irreversible expansion is :

where,

w = work done

= external pressure = 1.19 atm

= initial volume of gas = 3.42 L

= final volume of gas = 7.39 L

Now put all the given values in the above formula, we get :

Thus, the work done of path B is, -478.1 J

Answer:

The molality of solution=12.605 m

Explanation:

We are given that

Molar mass of Hydrogen peroxide, M=34 g/mol

Density of solution, [tex]\rho=1.11gcm^{-3}[/tex]

30% Means mass of solute (Hydrogen peroxide)=30 g

Mass of solvent =100-30=70 g

Total mass of solution, m=100 g

Number of moles of solute=[tex]\frac{given\;mass}{molar\;mass}[/tex]

Using the formula

Number of moles of hydrogen peroxide=[tex]\frac{30}{34}[/tex]

Now, molality of solution

[tex]m=\frac{number\;of\;moles\;of\;solute}{mass\;of\;solvent}\times 1000[/tex]

[tex]m=\frac{30}{70\times 34}\times 1000[/tex]

[tex]m=12.605 m[/tex]

Hence, the molality of solution=12.605 m

Answer:

Physical

Chemical

Explanation:

Intermolecular forces are the forces that hold the molecules of a substance together in a particular state of matter. They decide the physical properties of a substance.

The intra molecular forces are the bond forces that hold atoms together in molecules. The nature of this bonding determines the chemical properties of substances.

Answer:

Ca(OH)2 +CO2========CaCO3 +H2O

Explanation:

since the number of elements in the right is equal to that of the elements in the left side shows it is balanced

Answer:

2.772 seconds

Explanation:

Given that;

t1/2 = 0.693/k

Where;

t1/2 = half life of the reaction

k= rate constant

Note that decomposition is a first order reaction since the rate of reaction depends on the concentration of one reactant

t1/2 = 0.693/2.5 x 10-1 s-1

t1/2= 2.772 seconds

Answer:35.1g of CO2

Explanation:

C3H8+5O2------=3CO2+4H2O

Answer:

The answer is B. Carbonyl

Carbonyl is the functional group is used in other functional groups. Therefore, option (B) is correct.

A functional group with the formula C=O that is composed of a carbon atom double-bonded to an oxygen atom and is divalent at the C atom is known as a carbonyl group in organic chemistry.

A carbonyl gathering is a synthetically natural utilitarian gathering made out of a carbon iota twofold clung to an oxygen molecule - - > [C=O] The most straightforward carbonyl gatherings are aldehydes and ketones typically connected to another carbon compound.

A functional group with a carbon double bonded to an oxygen is called a carbonyl group. They have unsurprising properties, like extremity, instability, and reactivity.

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Answer:

c.sf4  b.2

Explanation:

Answer:

pH= 1.9 then [tex]H_{3} PO_{4}[/tex]

pH = 5.0 , [tex]CH_{3} COOH[/tex]

pH = 3.9 , HCOOH

As we know range left [tex]pH= pKa+/- 1[/tex]

Ethane consists of 6C−H bonds and 1C−C bond. Total number of bonds is 7. Each bond is made up of two electrons

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Answer:

0 J

Explanation:

Applying,

ΔE = q+w................ Equation 1

Where ΔE = change in internal energy of the system, q = Heat of the system, w = work of the system.

Note: q is positive, while w is negative

From the question,

Given: q = 425 J, w = -425 J

Substitute these values into equation 1

ΔE = 425-425

ΔE = 0 J

Hence the change in internal energy of the system is 0 J

Answer:

Option C

Explanation:

From the question we are told that:

Difference in energy [tex]\delta E =3.49 * 10^{-17} J[/tex]

The Ground state Difference in energy at n=1

[tex]\delta E_g = 2.18 * 10^{-18} × Z^2[/tex]

Generally the equation for Difference in energy is mathematically given by

[tex]\delta E=\delta E_g[/tex]

Therefore

[tex]3.49 * 10^{-17} = 2.18 * 10^{-18} * Z^2[/tex]

[tex]Z^2=16[/tex]

[tex]Z=4[/tex]

Therefore

Charge on element Z Q_Z

[tex]Q_Z= Atomic\ no\. of\ element - No.\ of\ electrons\ of\ element[/tex]

[tex]Q_Z =4-1[/tex]

[tex]Q_Z=+3[/tex]

Option C

Answer:

d. Mixing helps ensure that the measured pH is reflective of the entire solution.

Explanation:

Hello there!

In this case, according to the given information, it turns out possible for us to reason that the answer is d. Mixing helps ensure that the measured pH is reflective of the entire solution because mixing help us to move the ions all around the solution so it undergoes homogenization and the measured pH at any point of the solution will be the same.

Moreover, we need to keep in mind that the incomplete stirring leads to regions with more concentration of the acid or base, or what we know as a gradient of concentration, which may lead to a incorrect measurement.

Regards!

Answer: Organic compounds ending with the name (-ene) indicate that the compounds contain double bonds in their molecules.

Explanation:

Organic compounds are those molecules that contains carbon atoms (as their main element), hydrogen and oxygen which are usually present. The presence of numerous organic compounds is due to the following properties of carbon:

--> the exceptional ability of carbon atoms to catenate, that is, to combine with one another to form straight chains, branched chains or ring compounds containing many carbon atoms.

--> The ease with which carbon combines with hydrogen, oxygen, Nitrogen and halogens

--> The ability of carbon atoms to form single, DOUBLE or triple bonds.

The organic compound that has the name ending with -ene are known as the alkenes. The members of the alkene series are formed from the alkanes by the removal of two hydrogen atoms and the introduction of a DOUBLE BOND in the carbon chain. They are named after the corresponding alkanes by changing the -ane ending to -ene.

Note: the systematic name of a compound is formed from the root hydrocarbon by adding a suffix and prefixes to denote the substitution of the hydrogen atoms.

Answer:

0.17 g

Explanation:

Since the volume of gas collected is 132 mL, we need to find the number of moles of gas present in 132 mL.

So, number of moles, n = volume of gas, v/molar volume, V

n = v/V where v = 132 mL = 0.132 L and V = 22.4 L

So, substituting the values of the variables into the equation, we have

n = v/V

n = 0.132 L/22.4 L

n = 0.005893 mol

We then need to calculate the molar mass of CO, M = atomic mass of carbon + atomic mass of oxygen = 12 g/mol + 16 g/mol = 28 g/mol

Also, number of moles of gas, n = m/M where m = mass of CO and M = molar mass of CO

m = nM

m = 0.005893 mol × 28 g/mol

m = 0.165004 g

m ≅ 0.17 g to 2 significant digits

Answer:

+ axit

CH2=CH-CH2-COOH,

CH3-CH=CH-COOH (tính cả đồng phân hình học)

CH2=C(CH3)-COOH.

+ este

HCOOCH=CH-CH3 (tính cả đồng phân hình học)

HCOO-CH2-CH=CH2,

HCOOC(CH3)=CH2.

CH3COOCH=CH2

CH2=CH-COOCH3

Answer:

Hence the concentration of a MnO41- solution that has absorbance of 0.490 in the same cell at that wavelength is 0.3266.

Explanation:

Now A = el, el=const

Then,

[tex]A2 / A1 = C2/ C1\\\\0.49/ 0.48 = C2 / 0.32\\\\C2 = 0.3266[/tex]

Answer:

d the oxygen escapes.

Explanation:

Hello there!

In this case, according to the given information, it turns out firstly convenient for us to write out the chemical reaction taking place:

[tex]2KClO_3\rightarrow 2KCl+3O_2[/tex]

Thus, since both potassium chlorate and chloride are solid whereas oxygen is gaseous, it tends to scape as we are working in an open test tube and that is why the products side do not have the reactants, KCl and O2, to return the reactants side, KClO3 in agreement to the concept of equilibrium reaction. This situation can be solved by working in a closed container.

Therefore the answer is d the oxygen escapes.

Regards!