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Fittoniya [83]
3 years ago
14

Steel cranes can carry heavy steel beams thousands of feet high during skyscraper construction. This is an example of:

Chemistry
2 answers:
Ronch [10]3 years ago
6 0

The evolution of building techniques is your answer

Because building techniques become better, because of technology and better materials, we can now build steel cranes that can carry heavier things

hope this helps

beks73 [17]3 years ago
4 0

Hello!

The steel cranes lifting thousands of feet high during skyscraper construction is an example of the evolution of building techniques.

I hope it helps!

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What is the quantity of heat (in kJ) associated with cooling 185.5 g of water from 25.60°C to ice at -10.70°C?Heat Capacity of S
Cerrena [4.2K]

Taking into account the definition of calorimetry, sensible heat and latent heat,  the amount of heat required is 37.88 kJ.

<h3>Calorimetry</h3>

Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.

<h3>Sensible heat</h3>

Sensible heat is defined as the amount of heat that a body absorbs or releases without any changes in its physical state (phase change).

<h3>Latent heat</h3>

Latent heat is defined as the energy required by a quantity of substance to change state.

When this change consists of changing from a solid to a liquid phase, it is called heat of fusion and when the change occurs from a liquid to a gaseous state, it is called heat of vaporization.

  • <u><em>25.60 °C to 0 °C</em></u>

First of all, you should know that the freezing point of water is 0°C. That is, at 0°C, water freezes and turns into ice.

So, you must lower the temperature from 25.60°C (in liquid state) to 0°C, in order to supply heat without changing state (sensible heat).

The amount of heat a body receives or transmits is determined by:

Q = c× m× ΔT

where Q is the heat exchanged by a body of mass m, made up of a specific heat substance c and where ΔT is the temperature variation.

In this case, you know:

  • c= Heat Capacity of Liquid= 4.184 \frac{J}{gC}
  • m= 185.5 g
  • ΔT= Tfinal - Tinitial= 0 °C - 25.60 °C= - 25.6 °C

Replacing:

Q1= 4.184 \frac{J}{gC}× 185.5 g× (- 25.6 °C)

Solving:

<u><em>Q1= -19,868.98 J</em></u>

  • <u><em>Change of state</em></u>

The heat Q that is necessary to provide for a mass m of a certain substance to change phase is equal to

Q = m×L

where L is called the latent heat of the substance and depends on the type of phase change.

In this case, you know:

n= 185.5 grams× \frac{1mol}{18 grams}= 10.30 moles, where 18 \frac{g}{mol} is the molar mass of water, that is, the amount of mass that a substance contains in one mole.

ΔHfus= 6.01 \frac{kJ}{mol}

Replacing:

Q2= 10.30 moles×6.01 \frac{kJ}{mol}

Solving:

<u><em>Q2=61.903 kJ= 61,903 J</em></u>

  • <u><em>0 °C to -10.70 °C</em></u>

Similar to sensible heat previously calculated, you know:

  • c = Heat Capacity of Solid = 2.092 \frac{J}{gC}
  • m= 185.5 g
  • ΔT= Tfinal - Tinitial= -10.70 °C - 0 °C= -10.70 °C

Replacing:

Q3= 2.092 \frac{J}{gC} × 185.5 g× (-10.70) °C

Solving:

<u><em>Q3= -4,152.3062 J</em></u>

<h3>Total heat required</h3>

The total heat required is calculated as:  

Total heat required= Q1 + Q2 +Q3

Total heat required=-19,868.98 J + 61,903 J -4,152.3062 J

<u><em>Total heat required= 37,881.7138 J= 37.8817138 kJ= 37.88 kJ</em></u>

In summary, the amount of heat required is 37.88 kJ.

Learn more about calorimetry:

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7 0
2 years ago
If the volume of a cylinder is reduced from 8.0 liters to 4.0 liters, the pressure of the gas in the cylinder will change from 7
Elza [17]

Answer:

P₂ = 140 KPa

Explanation:

Given data:

Initial volume = 8.0 L

Final volume = 4.0 L

Initial pressure = 70 KPa

Final pressure = ?

Solution:

According to Boyle's law

P₁V₁ = P₂V₂

P₂ = P₁V₁  / V₂

P₂ = 70 KPa ×8.0 L/4.0 L

P₂ = 560 KPa .L / 4.0 L

P₂ = 140 KPa

6 0
3 years ago
An acid sample of an unknown concentration is contained in a erlenmeyer flask. Which technique below would be best suited to ana
Ivenika [448]

Answer:

Titration

Explanation:

The best technique which can be used to determine the number of moles of the HCl in the sample is titration.

The given amount of HCl solution must be titrated with known concentration of the base like NaOH.

The volume of NaOH required must be noted also.

According to the reaction,

NaOH+HCl\rightarrow NaCl+H_2O

At equivalence point

Moles of HCl = Moles of NaOH

Considering:-

Moles of HCl=Molarity_{NaOH}\times Volume_{NaOH}

Thus, in this way, moles of HCl can be determined.

4 0
3 years ago
5,6-dimethyl-2-heptyne <br><br> Due in 1 hr pls help me
mina [271]

Answer:

Please see the attached pictures.

Explanation:

☆ To ensure that each carbon has 4 bonds, fill the other bonds with Hs.

4 0
3 years ago
Ionic compounds are typically between a​
barxatty [35]
It starts with a cation and ends with a nonmetal anion. To recap, cations are your positively charged elements and anions are negatively change and usually with the ending “ide”. For example, potassium a metal and chlorine a nonmetal (KCl) would form the word potassium chloride.
8 0
4 years ago
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