The answer would be A) Physical Change. When the silver tarnishes it is still remnants of silver. If it were B, the silver would change into a different substance.

6 0

3 years ago

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Assuming we have 100.0 g of element A, how much will be left after 4 half lives?

Vlada [557]

Answer:

Explanation:

because 100 divided by4 is 25

4 0

2 years ago

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2) An ideal gas flows through a horizontal tube at steady state. No heat is added and no shaft work is done. The cross- sectiona

aleksandrvk [35]

Answer:

The temperature of the nitrogen gas at another section is $148.8^{o}C$

Explanation:

Energy balance equation for steady state flow of gas under negiligible potential energy.

The negligible heat transfer and no shaft work is as follows.

$\Delta H+\frac{\Delta u^{2}}{2}=Q+W$

$\Delta H+\frac{\Delta u^{2}}{2}=0..........(1)$

$\Delta H$ is enthalphy of gas and it is changes with the temperature.

$\Delta H=C_{p}(T_{2}-T_{1}).................(2)$

$C_{p}$ = Molar heat capacity of the gas at constant pressure. $T_{1}$ = Initial temperature at section 1

$T_{2}$ = Final temperature at section 2

Substitute the equation (2) in equation (1)

$C_{p}(T_{2}-T_{1})+\frac{u_{2}^2-u_{1}^2}{2}=0$

Solve the above equation is as follows.

$T_{2}=T_{1}-\frac{u_{2}^{2}-u_{1}^{2}}{2}=0...............(3)$

From the given,

$T_{1}=150+273=423K$

$C_{p}=\frac{7R}{2}$

$u_{1}=2.5\,m/s$

$u_{2}=50\,m/s$

Molar mass of nitrogen gas = 0.02802 kg/mol

Substitute the all values in the equation (3)

$T_{2}=423K-\frac{(50m/s)^{2}-(2.5m/s)^{2}}{2\times \frac{7}{2}\times8.314\,J\,mol^{-1}K^{-1}}\times \frac{J/kg}{m^{2}/s^{2}}\times \frac{0.02802\,kg}{mol}$

=421.8K=148.8^{o}C

Therefore,The temperature of the nitrogen gas at another section is $148.8^{o}C$ .

3 0

3 years ago