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4 years ago

Compare and contrast the different way heat moves

1 answer:

7 0

Convection is the transfer of heat energy in a gas or liquid by movement of currents. (It can also happen is some solids, like sand.) The heat moves with the fluid.

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Describe the relationship between the mole information of a substance and it's chemical formula. Summarize fill in the blanks to

Umnica [9.8K]

Find the Molecular mass of all atoms in the chemical formula and divide it with the mass of the sunstance to get the amount of moles

5 0

3 years ago

Explain why air is not a good conductor of heat.

Masja [62]

In a gas molecules have to scatter off molecules to exchange energy in larger distances, so the probability of transfer is much smaller. Air is a bad conductor because, to conduct heat current molecules should absorb heat and transmit it to neighbor by vibrating.

8 0

3 years ago

Read 2 more answers

A calorimeter contains 35.0 mLmL of water at 15.0 ∘C∘C . When 2.20 gg of XX (a substance with a molar mass of 56.0 g/molg/mol )

Temka [501]

Answer:

ΔH rx = -43.5 kJ / mol

Explanation:

In water, Xdissolves thus:

X(s) + H₂O(l) → X(aq) + H₂O(aq)

It is possible to find the heat in dissolution process using coffee cup calorimeter equation:

Q = -m×C×ΔT

Where Q is heat, m is mass of solution (35.0g -density 1g/mL- + 2.20g = 37.2g), C is specific heat of solution (4.18J/g°C), and ΔT is change in temperature (26.0°C-15.0°C = 11.0°C)

Replacing:

Q = -37.2g×4.18J/g°C×11.0°C

Q = -1710J = -1.71kJ

As enthalpy is the change in heat per mole of reaction, moles of X that reacted were:

2.20g X × (1mol / 56.0g) = 0.0393 moles

As heat produced per 0.0393moles was -1.71kJ, heat per mole of X is:

-1.71kJ / 0.0393mol = -43.5 kJ / mol = ΔH rx

6 0

3 years ago

A closed, frictionless piston-cylinder contains a gas mixture with the following composition on a mass basis: 40% carbon dioxide

Hitman42 [59]

Answer:

W=-37.6kJ, therefore, work is done on the system.

Explanation:

Hello,

In this case, the first step is to compute the moles of each gas present in the given mixture, by using the total mixture weight the mass compositions and their molar masses:

$n_{CO_2}=0.8kg*0.4*\frac{1kmolCO_2}{44kgCO_2}= 0.00727kmolCO_2\\\\n_{O_2}=0.8kg*0.25*\frac{1kmolO_2}{32kgO_2}=0.00625kmolO_2\\ \\n_{Ne}=0.8kg*0.35*\frac{1kmolNe}{20.2kgNe}=0.0139kmolNe$

Next, the total moles:

$n_T=0.00727kmol+0.00625kmol+0.0139kmol=0.02742kmol$

After that, since the process is isobaric, we can compute the work as:

$W=P(V_2-V_1)$

Therefore, we need to compute both the initial and final volumes which are at 260 °C and 95 °C respectively for the same moles and pressure (isobaric closed system)

$V_1=\frac{n_TRT_1}{P}= \frac{0.02742kmol*8.314\frac{kPa*m^3}{kmol\times K}*(260+273)K}{450kPa}=0.27m^3\\ \\V_2=\frac{n_TRT_2}{P}= \frac{0.02742kmol*8.314\frac{kPa*m^3}{kmol\times K}*(95+273)K}{450kPa}=0.19m^3$

Thereby, the magnitude and direction of work turn out:

$W=450kPa(0.19m^3-0.27m^3)\\\\W=-37.6kJ$

Thus, we conclude that since it is negative, work is done on the system (first law of thermodynamics).

Regards.

7 0

3 years ago

The air bags in automobiles were once inflated by nitrogen gas generated by the rapid decomposition of

Basile [38]

Answer:

1.57 mol NaN₃

Explanation:

2 NaN₃ (s) → 2 Na (s) + 3 N₂ (g)

First we use PV=nRT to calculate the number of N₂ moles that need to be produced:

P = 1.07 atm

V = 53.4 L

n = ?

R = 0.082 atm·L·mol⁻¹·K⁻¹

T = 23.7 °C ⇒ 23.7 + 273.16 = 296.86 K

Inputing the data:

1.07 atm * 53.4 L = n * 0.082 atm·L·mol⁻¹·K⁻¹ * 296.86

And solving for n:

n = 2.35 mol N₂

Finally we convert N₂ moles into NaN₃ moles, using the stoichiometric coefficients of the balanced reaction:

2.35 mol N₂ * $\frac{2molNaN_3}{3molN_2}$ = 1.57 mol NaN₃

4 0

3 years ago