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sweet [91]
3 years ago
15

Medical cold packs can use various chemicals in order to produce a cold compress to help reduce inflammation caused by injuries.

Based on the accepted value in Question 1, how many grams of potassium chloride would have to be dissolved into 750 g of 20.0°C water to produce a 4.0°C solution? (Remember: specific heat of water is 4184 J/g·°C) 92 4.
Chemistry
2 answers:
Paha777 [63]3 years ago
6 0

Answer:

We need 217.7 grams of KCl

Explanation:

Medical cold packs can use various chemicals in order to produce a cold compress to help reduce inflammation caused by injuries. Based on the accepted value of 17.2 kJ/mol, how many grams of potassium chloride would have to be dissolved into 750 g of 20.0 degree Celsius water to produce a 4.0 degree Celsius solution?

Step 1: Data given

Mass of water = 750 grams

Temperature = 20.0 °C

Temperature of the solution = 4.0 °C

Specific heat of water 4.184 J/g°C

Step 2: Calculate the heat

Q = m* c * ΔT

⇒with Q = the heat transfer = TO BE DETERMINED

⇒with m = the mass of water = 750 grams

⇒with c = the specific heat of water = 4.184 J/g°C

⇒with ΔT = The change of temperature = 16 °C

Q = 750 * 4.184 * 16

Q = 50208 J = 50.2 kJ

Step 3: Calculate moles KCl

Moles KCl = 50.2 kJ / 17.2 kJ/mol

Moles KCl = 2.92 moles

Step 4: Calculate mass KCl

Mass KCl = moles KCl * molar mass KCl

Mass KCl = 2.92 moles * 74.55 g/mol

Mass KCl = 217.7 grams

We need 217.7 grams of KCl

Illusion [34]3 years ago
3 0

Answer:

Mass of KCL = 218 grams.

Explanation:

Step 1: calculate the heat that must be absorbed(q).

Heat that must be absorbed(q) is calculated as follows:

q= m c (T2-T1).

q = 750g (4.18 J/gC)(20-4 C) = 5.016X10^4 J = 50.16 kJ

Step 2: we determine moles of KCL as follows:

Moles KCl = 50.16 kJ / 17.2 kJ/mol = 2.92 moles.

Step 3: calculate mass of KCL:

Mass of KCl = 2.92 mol X 74.55 g/mol = 218g.

Therefore, 218 grams of KCL would have to be dissolved into 750 g of 20.0°C H2O to produce the solution.

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Answer:

It takes 1,068.76 grams of nitrogen to fill an 855 L tank at STP.

Explanation:

The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C or 273.15 °K are used and are reference values for gases.

On the other side, the pressure, P, the temperature, T, and the volume, V, of an ideal gas, are related by a simple formula called the ideal gas law:  

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So, in this case:

  • P= 1 atm
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Replacing:

1 atm* 855 L= n* 0.082 \frac{atm*L}{mol*K} * 273.15 K

Solving:

n=\frac{1 atm* 855 L}{0.082\frac{atm*L}{mol*K} *273.15 K }

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Answer: Option (B) is the correct answer.

Explanation:

Expression for the given decomposition reaction is as follows.

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Initial :               x                   0

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Putting the given values into the above formula as follows.

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                2 \times (x - 0.1) = (0.2)^{2}

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This means that P_{N_{2}O_{4}} = x = 0.12 atm.

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