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3 years ago

When energy is added to a substance at constant volume and pressure, its temperature increases except ________.

Chemistry

1 answer:

Travka [436]3 years ago

7 0

A. When the substance is in its gaseous state.

<u>Explanation:</u>

When a substance is expanding against its constant volume and pressure, its temperature increases except when the substance is in gaseous state and not in liquid or solid state. So the internal energy increase in the system not only increases and maintaining the volume and pressure of the system remains constant in its gaseous phase. In the first law of Thermodynamics, it is used specifically that to especially in the case of gaseous system.

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A compound contains only nitrogen and oxygen and is 30.5% nitrogen by mass. A gaseous sample of the compound has a density of 3.

MariettaO [177]

Answer : The molecular formula of the compound will be, $NO_4$

Explanation:

First we have to calculate the mass of nitrogen and oxygen.

As we are given that 30.5 % nitrogen by mass that means 30.5 g of nitrogen present in 100 g of solution.

Mass of nitrogen = 30.5 g

Mass of oxygen = Mass of solution - Mass of nitrogen

Mass of oxygen = 100 g - 30.5 g

Mass of oxygen = 69.5 g

To formulate the empirical formula, we need to follow some steps:

Step 1: Converting the given masses into moles.

Moles of N = $\frac{\text{Given mass of N}}{\text{Molar mass of N}}=\frac{30.5g}{28g/mole}=1.09moles$

Moles of O = $\frac{\text{Given mass of O}}{\text{Molar mass of O}}=\frac{69.5g}{16g/mole}=4.34moles$

Step 2: Calculating the mole ratio of the given elements.

For the mole ratio, we divide each value of the moles by the smallest number of moles calculated which is 1.09 moles.

For N = $\frac{1.09}{1.09}=1$

For O = $\frac{4.34}{1.09}=3.98\approx 4$

Step 3: Taking the mole ratio as their subscripts.

The ratio of N : O = 1 : 4

Hence, the empirical formula for the given compound is $NO_4$

The empirical mass of given compound is $NO_4$ = 1(28) + 4(16) = 92 g/eq

To calculate the molecular mass of compound we are using ideal gas equation:

$PV=nRT\\\\PV=\frac{w}{M}RT\\\\P=\frac{w}{V}\\times \frac{RT}{M}\\\\P=\rho \frac{RT}{M}$

where,

P = pressure of gas = 924 torr = 1.216 atm

Conversion used : (1 atm = 760 torr)

T = temperature of gas = $105^oC=273+105=378K$

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

$\rho$ = density of gas = 3.61 g/L

M = molar mass of gas = ?

Now put all the given values in the ideal gas equation, we get:

$(1.216atm)=3.61g/L\times \frac{(0.0821L.atm/mole.K)\times (378K)}{M}$

$M=92.1g/mol$

Now we have to calculate the molecular formula of the compound.

The equation used to calculate the valency is :

$n=\frac{\text{molecular mass}}{\text{empirical mass}}$

$n=\frac{92.1}{92}=1$

Molecular formula = $(NO_4)_n=(NO_4)_1=NO_4$

Thus, the molecular formula of the compound will be, $NO_4$

4 0

4 years ago

Which particle changes to create an isotope of an atom? <br> A.proton<br> B.neutron<br> C.electron

Dovator [93]

Answer:

Explanation:

proton

5 0

3 years ago

Dissolving continues until an equilibrium is established.<br> O True<br> O False

vazorg [7]

Answer: It’s true

Explanation:

7 0

3 years ago

What does 3.5 degree of unsaturation tell you?

Kaylis [27]

Answer:

It means the chemical entity is a radical

Explanation:

When we talk of unsaturation, we are referring to the number of pi-bonds in a chemical entity. The alkane, alkene and alkyne organic family are used to as common examples to explain the term unsaturation.

While alkynes have 3 bonds, it must be understood that they have 2 pi bonds only and as such their degree of saturation is two.

In the case of an alkene, there is only one single pi bond and as such the degree of unsaturation is 1.

Now in this case, we have a fractional 0.5 degree of unsaturation alongside the 3 to make a total of 3.5. So what’s the issue here?

The fractional part shows that the chemical entity we are dealing with here is a radical. While the integer 3 shows that there are 3 pi-bonds, the half pi bond remaining tells us that there is a missing electron on one of the atoms involved in the chemical bonding and as such, the 1/2 extra degree of unsaturation tends to tell us this.

Kindly recall that a radical is a chemical entity within which we have at the least an unpaired electron.

5 0

3 years ago

Explain why aluminum does not react with potassium nitrate (KNO3) although it reacts with copper nitrate

Ratling [72]

Answer:

Potassium is more reactive than aluminium, so no reaction takes place. But aluminium is more reactive than copper, so it replaces the copper in copper nitrate

<h3>Explanation:</h3>

More reactive metal compound + less reactive metal

-> no reaction

However

Less reactive metal compound + more reactive metal

-> more reactive metal compound + less reactive metal

This is called substitution reaction where the more reactive metal replaces the less reactive metal in the compound.

7 0

3 years ago