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3 years ago

7

If rust is scraped off a nail, and the nail is shiny on the inside, the inside wasA.chemically changed also.B.not chemically cha

nged.C.physically and chemically changed.D.neither physically nor chemically changed.

1 answer:

aliya0001 [1]3 years ago

3 0

Answer: D.neither physically nor chemically changed.

Explanation:

A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these reactions.

Example: Melting of ice

A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these reactions.

Example: Corrosion of iron

As the inside of the nail was still shiny and in same phase, that means it has not undergone any physical or chemical change.

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For the reaction

s2008m [1.1K]

Answer:

0.558mole of SO₃

Explanation:

Given parameters:

Molar mass of SO₃ = 80.0632g/mol

Mass of S = 17.9g

Molar mass of S = 32.065g/mol

Number of moles of O₂ = 0.157mole

Molar mass of O₂ = 31.9988g/mol

Unknown:

Maximum amount of SO₃

Solution

We need to write the proper reaction equation.

2S + 3O₂ → 2SO₃

We should bear in mind that the extent of this reaction relies on the reactant that is in short supply i.e limiting reagent. Here the limiting reagent is the Sulfur, S. The oxygen gas would be in excess since it is readily availbale.

So we simply compare the molar relationship between sulfur and product formed to solve the problem:

First, find the number of moles of Sulfur, S:

Number of moles of S = $\frac{mass }{molar mass}$

Number of moles of S = $\frac{17.9 }{32.065}$ = 0.558mole

Now to find the maximum amount of SO₃ formed, compare the moles of reactant to the product:

2 mole of Sulfur produced 2 mole of SO₃

Therefore; 0.558mole of sulfur will produce 0.558mole of SO₃

5 0

3 years ago

The The thermal conductivity of a sheet of rigid, extruded insulation is reported to be k=0.029 W/ m measured temperature differ

vfiekz [6]

Answer:

Heat flux = 13.92 W/m2

Rate of heat transfer throug the 3m x 3m sheet = 125.28 W

The thermal resistance of the 3x3m sheet is 0.0958 K/W

Explanation:

The rate of heat transfer through a 3m x 3m sheet of insulation can be calculated as:

$q=-k*A*\frac{\Delta T}{\Delta X}\\\\q=-0.029\frac{W}{m*K}*(3m*3m)*\frac{12K}{0.025m} =125.28W$

The heat flux can be defined as the amount of heat flow by unit of area.

Using the previous calculation, we can estimate the heat flux:

$heat \, flux=\frac{q}{A}=\frac{125.28 W}{9 m^{2} } =13.92 W/m^{2}$

It can also be calculated as:

$q/A=-k*\frac{\Delta T}{\Delta X}$

The thermal resistance can be expressed as

$\Delta T=R_t*Q\\R_t=\Delta T/Q=\frac{\Delta X}{k*A}$

For the 3m x 3m sheet, the thermal resistance is

$R_t = \frac{\Delta X}{k*A}=\frac{0.025m}{0.029W/mK*9m^{2}}=0.0958 \, K/W$

4 0

3 years ago

A 25.0 mL aliquot of 0.0680 M EDTA was added to a 59.0 mL solution containing an unknown concentration of V3 . All of the V3 pre

givi [52]

Answer:

$\mathbf{0.02 M}$

Explanation:

$\text{So, from the given question:}$

$\text{EDTA will make complex with}$ $V^{+3}$ $\text{and the remaining EDTA will react with }$ $Ga^{+3}$

$\text{Hence, the total concentration of}$ $V^{+3}$ & $Ga^{+3}$ $\text{will be equivalent to EDTA concentration.}$

$V_{EDTA} = 25 \ mL$

$V_{V^{+3}} = 59.0 \ mL$

$V_{Ga^{+3}} = 13.0 \ mL$

$M_{EDTA} = 0.0680 \ M$

$M_{V^{+3}} = ???(unknown)$

$M_{Ga^{+3}} = 0.0400 \ M$

$V^{+3} + EDTA \to V[EDTA] + EDTA(Excess) \to^{CoA} \ Ga[EDTA] _{complex}$

$M_{EDTA} \times V_{EDTA} = ( V_{V^+3}\times M_{V^{+3}}+ V_{Ga^{+3} }\times M_{Ga^{+3}}})$

$0.0680 \times 25 = (59\times x + 13 \times 0.040) \\ \\ 1.7 = 59x + 0.52\\ \\ 1.7 - 0.52 = 59x \\ \\ 59x = 1.18$

$x = \dfrac{1.18}{59}$

$\mathbf{x =0.02 \ M }$

5 0

3 years ago

I have a question about ionization energy.

ValentinkaMS [17]

Ionization energy is the measure of the extend to which the nucleus attracts the outermost electron
if ionization energy us high than force of attraction Is high so it is not easy to remove and vice versa .
hope you understand.....

5 0

3 years ago

At a certain temperature the vapor pressure of pure methanol is measured to be . Suppose a solution is prepared by mixing of met

CaHeK987 [17]

Answer:

Partial pressure is 0.13 atm

Explanation:

CHECK THE COMPLETE QUESTION BELOW :

At a certain temperature, the vapor pressure of pure methanol is measured to be 0.43atm. Suppose a solution is prepared by mixing 88.2 g of methanol and 116.g of water. Calculate the partial pressure of methanol vapor above this solution. Be sure your answer has the correct number of significant digits. Note for advanced students: you may assume the solution is ideal.

Using Raoult´s law for ideal soultions we have

P(A) = X(A) *Pº(A)

where P(A) is the partial vapor pressure pressure of methanol,

X(A) is the mole fraction of solute (methanol) in solution,

Pº(A) is the vapor pressure of pure solute

Raoult's law states that the vapor pressure of a solution is dependent on the mole fraction of a solute added to the solution.

Raoult's law can be expressed below

Psolution = ΧsolventP0solvent.

Expressing it interns of the constituents given in the question we have

P(CH₃OH) = X(CH₃OH) x Pº(CH₃OH)

To calculate the mole fraction of CH₃OH, we make use of the formula below :

X(A) = mol (A) / ntotal

Ntotal = (sum of number of moles of A )+( moles solvent)

mol (CH₃3OH) can be calculated as :: 88.2 g/ 32 g/mol = 2.76 mol of CH₃OH

mol (H₂O) can be calculated as ::116 g/ 18 g/mol = 6.44 mol

total n = (6.44 + 2.76) mol = 9.20 mol

To calculate the partial pressure the we say;

P(CH₃OH) = (2.76 mol CH + 9.20 mol) x( 0.43 atm) = 0.13 atm

Hence, the partial pressure rounded to two significant figures is 0.13 atm

8 0

3 years ago