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sergejj [24]
3 years ago
15

Can you please answer number 8 thanks

Chemistry
1 answer:
MAXImum [283]3 years ago
4 0
A day is added to February every four tears as a corrective measure. The Earth does not exactly revolve around the sun for 365 days. There is a small offset that is corrected by adding a day to February. This happens every four years and it is called Leap year.
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A horizontal pipe 15 cm in diameter and 4 m long is buried in the earth at a depth of 20 cm. The pipe-wall temperature is 75 deg
Basile [38]

Explanation:

The given data for case (1) is as follows.

  h = 20 cm = 0.2 m

Assuming that a rectangular slab is placed above the pipe and we will calculate the heat transfer as follows.

              Q = kA \frac{\Delta T}{L}

  where,    A = area

                  L = length

                  k = thermal conductivity = 0.8 W/m

             \Delta T = change in temperature.

Therefore, putting the given values into the above formula as follows.

            Q = kA \frac{\Delta T}{L}

                = 0.8 W/m \times (4 m \times 0.15 m) \frac{75 - 5}{0.2}

                = 168 W

For case (2), h = 180 cm = 1.8 m

Therefore, heat lost will be calculated as follows.

                       Q = kA \frac{\Delta T}{L}

                           = 0.8 W/m \times (4 m \times 0.15 m) \frac{75 - 5}{1.8}

                           = 18.67 W

Thus, we can conclude that 18.67 W heat lost if the pipe was buried at a depth of 180 cm.

8 0
3 years ago
Determine the enthalpy for this reaction: Al(OH)3(s)+3HCl(g)→AlCl3(s)+3H2O(l)
ivanzaharov [21]
<span>Important information to solve the exercise :
Substance ΔHf (kJ/mol):
HCl(g)= −92.0 </span><span>kJ/mol
Al(OH)3(s)= −1277.0 </span><span><span>kJ/mol
</span> H2O(l)= −285.8 </span><span>kJ/mol
AlCl3(s) =−705.6 </span><span>kJ/mol

</span><span>Al(OH)3(s)+3HCl(g)→AlCl3(s)+3H2O(l)
    reactants                         products

products- reactants:</span><span>

(−705.6) + (3 x −285.8) - ( −1277.0 ) - (3 x −92.0 ) = - 10.0 </span>kJ per mole at 25°C
<span>
</span>






6 0
3 years ago
Freezing a candy bar is an example of a physical change. <br> True or false
Debora [2.8K]

Answer: This is true.

Explanation:  

 It is true because if becomes frozen, then it is physically harder to melt...

6 0
2 years ago
Given that 25.0 mL of mercury has a mass of 340.0 g, calculate (a) the density of mercury and (b) the mass of 120.0 mL of mercur
natita [175]

Answer :

(a) The density of mercury is, 13.6 g/ml

(b) The mass of 120.0 ml of mercury is, 1632 grams

Explanation :

(a) Now we have to calculate the density of mercury.

<u>Given :</u>

Volume of mercury = 25.0 ml

Mass of mercury = 340.0 g

Formula used :

\text{Density of mercury}=\frac{\text{Mass of mercury}}{\text{Volume of mercury}}

\text{Density of mercury}=\frac{340.0g}{25.0ml}=13.6g/ml

Therefore, the density of mercury is, 13.6 g/ml

(b) Now we have to calculate the mass of 120.0 ml of mercury.

As, 25.0 ml of mercury has mass = 340.0 g

So, 120.0 ml of mercury has mass = \frac{120.0ml}{25.0ml}\times 340.0g=1632g

Therefore, the mass of 120.0 ml of mercury is, 1632 grams

3 0
3 years ago
When light strikes a transparent material, most of the light is absorbed or reflected.
Monica [59]
When light strikes a transparent material, most of the light passes through it it doesn't absorb or reflect it 
4 0
3 years ago
Read 2 more answers
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