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3 years ago

A 12 gram piece of Cu at 475 oC is placed in contact with a 15 gram piece of Cr at 265 oC.

Chemistry

1 answer:

ale4655 [162]3 years ago

4 0

Answer:

349.22°C

Explanation:

Let the final temperature of the two pieces of metal be x.

Now, the warmer metal which is C u reduces from 475°C to x. Thus Δt for C u is; Δt1 = 475 - x.

The cooler metal Cr increases in temperature from 265°C to x. Thus, it's change in temperature is Δt for Cr is; Δt2 = x - 265.

Now from conservation of energy, the amount of energy leaving the C u metal is equal to the amount of energy entering the Cr metal.

Thus;

q_lost = q_gain

Where;

q_lost = m1•c1•Δt1

q_gained = m2•c2•Δt2

Now, c1 & c2 are the specific heat capacity of C u and Cr respectively.

From online tables, c1 = 0.385 J/g°C and c2 = 0.46 J/g°C

We are given;

m1 = 12g and m2 = 15g

Thus;

12 × 0.385 × (475 - x) = 15 × 0.46 × (x - 265)

2194.5 - 4.62x = 6.9x - 1828.5

6.9x + 4.62x = 2194.5 + 1828.5

11.52x = 4023

x = 4023/11.52

x = 349.22°C

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A gold coin contains 3.47 × 10^23 gold atoms. What is the mass of the coin in grams?

VashaNatasha [74]

Answer:

Mass = 114.26 g

Explanation:

Given data:

Number of gold atoms = 3.47×10²³ atoms

Mass in gram = ?

Solution:

The given problem will solve by using Avogadro number.

It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance. The number 6.022 × 10²³ is called Avogadro number.

1 mole = 6.022 × 10²³ atoms

3.47×10²³ atoms × 1 mol /6.022 × 10²³ atoms

0.58 mol

Mass of gold:

Mass = number of moles × molar mass

Mass = 0.58 mol × 197 g/mol

Mass = 114.26 g

4 0

3 years ago

The gauge pressure inside a vessel is ‐40kPa, at an elevation of 5000m. a) What is the absolute pressure? b) At this elevation,

hoa [83]

Answer:

a) Pabs = 48960 KPa

b) T = 433.332 °C

Explanation:

Pabs = Pgauge + d*g* h

∴ d = 1000 Kg/m³

∴ g = 9.8 m/s²

∴ h = 5000 m

∴ P gauge = - 40 KPa * ( 1000 Pa / KPa ) = - 40000 Pa; Pa≡Kg/m*s²

⇒ Pabs = - 40000 Kg/ms² + ( 1000 Kg/m³ * 9.8 m/s² * 5000 m )

⇒ Pabs = 48960000 Pa = 48960 KPa

a) at that height and pressure, we find the temperature at which the water boils by means of an almost-exponential graph which has the following equation:

P(T) = 0.61094 exp ( 17.625*T / ( T + 243.04 ))......P (KPa) ∧ T (°C)....from literature

∴ P = 48960 KPa

⇒ ( 48960 KPa / 0.61094 ) = exp ( 17.625T / (T+ 243.04))

⇒ 80138.803 = exp ( 17.625T / ( T + 243.04))

⇒ Ln ( 80138.803) = 17.625T / ( T + 243.04))

⇒ 11.292 * ( T + 243.04 ) = 17.625T

⇒ 11.292T + 2744.289 = 17.625T

⇒ 2744.289 = 17.625T - 11.292T

⇒ 2744.289 = 6.333T

⇒ T = 433.332 °C

3 0

3 years ago

2 Points

djyliett [7]

A. Camouflage Fur is the correct answer.

7 0

3 years ago

A 25.00 g solid sample of Ca(OH)2 was added into 1250 mL of 0.400 M HCl aqueous solution. The temperature of the solution was de

daser333 [38]

Answer:

86.735 kJ

Explanation:

Simply multiply the change in temperature by the Ccal;

(36.6 - 20.0)×5.225 = 86.735

5 0

3 years ago

An average person expends about 845 kilojoules of energy per hour of walking. Suppose a person eats 2 baked potatoes with butter

ExtremeBDS [4]

Answer:

$\large\boxed{2hours}$

Explanation:

You will need to use the conversion between food calories, calories and joules.

$1\text { nutritional calorie }= 1,000cal\\ \\ 1cal=4.184joule$

From a nutritional table (from the internet) you can obtain the amount of nutritional calories for each type macronutrient: carbohydrates, protein, and fat.

Macronutrient food calories

Carbohydrate 4 cal/g

Protein 4 cal/g

Fat 9 cal/g

To convert food calories to regular calories, mutiply by the conversion factor:

$1=1,000cal/\text{nutritional calorie}$

Macronutrient calories

Carbohydrate 4,000 cal/g

Protein 4,000 cal/g

Fat 9,000 cal/g

To convert regular calories to joules, multiply by the conversion factor:

$1=4.184 joule/1cal$

Macronutrient energy in joules

Carbohydrate 16,736 joule/g

Protein 16,736 joule/g

Fat 37,656 joule/g

Now you can multiply the grams of each macronutrient in one potato by its energy content:

Macronutrient energy/gram × grams = total energy

Carbohydrate 16,736 joule/g × 37 g = 619,232 joules

Protein 16,736 joule/g × 4.3 g = 71,968.8 joules

Fat 37,656 joule/g × 4 g = 150,624 joules

Total = 619,232 joules + 71,968.8 joules + 150,624 joules = 841,820.8 joules.

Since they are two potatoes, multiply by 2: × 841,820.8 joules = 1,683,641.6 joules.

Divide by 1,000 to convert to kilojoules = 1,683.64 kilojoules

Divide the total energy from the two potatoes by the energy that an average person expend per hour of walking (845 kilojoules of energy per hour):

$1,683.64kilojoules/845kilojouesl/hour=1.99hours\approx 2hours$

7 0

3 years ago