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kirza4 [7]
3 years ago
13

A volume of 125 mL of H2O is initially at room temperature (22.00 ∘C). A chilled steel rod at 2.00 ∘C is placed in the water. If

the final temperature of the system is 21.30 ∘C , what is the mass of the steel bar?Use the following values:specific heat of water = 4.18 J/(g⋅∘C)specific heat of steel = 0.452 J/(g⋅∘C)Express your answer to three significant figures and include the appropriate units.mass of the steel =
Chemistry
1 answer:
VMariaS [17]3 years ago
3 0

Answer:

41.9 g

Explanation:

We can calculate the heat released by the water and the heat absorbed by the steel rod using the following expression.

Q = c × m × ΔT

where,

c: specific heat capacity

m: mass

ΔT: change in temperature

If we consider the density of water is 1.00 g/mol, the mass of water is 125 g.

According to the law of conservation of energy, the sum of the heat released by the water (Qw) and the heat absorbed by the steel (Qs) is zero.

Qw + Qs = 0

Qw = -Qs

cw × mw × ΔTw = -cs × ms × ΔTs

(4.18 J/g.°C) × 125 g × (21.30°C-22.00°C) = -(0.452J/g.°C) × ms × (21.30°C-2.00°C)

ms = 41.9 g

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IceJOKER [234]

<u>Concepts used:</u>

1 mole of an element or a compound has 6.022 * 10²³ formula units

So, we can say that: <em>Number of formula units = number of moles * 6.022*10²³</em>

number of moles of an element or a compound = given mass/molar mass

<u>__________________________________________________________</u>

<u>003 - </u><u>Number of CaH₂ formula units in 6.065 grams</u>

Number of Moles:

We know that the molar mass of CaH₂ is 42 grams/mol

Number of Moles of CaH₂ = given mass/molar mass

Number of moles = 6.065 / 42

Number of moles = 0.143 moles

Number of Formula units:

Number of formula units = number of moles * 6.022*10²³

= 0.143 * 6.022 * 10²³

= 0.86 * 10²³ formula units

__________________________________________________________

<u>004 </u><u>- Mass of 6.34 * 10²⁴ formula units of NaBF₄</u>

Number of Moles:

We mentioned this formula before:

<em>Number of formula units = number of moles * 6.022*10²³</em>

Solving it for number of moles, we get:

Number of moles = Number of Formula units / 6.022* 10²³

replacing the variable

Number of moles = 6.34 * 10²⁴ / 6.022*10²³

Number of moles=  10.5 moles

Mass of 10.5 moles of NaBF₄:

Molar mass of NaBF₄ = 38 grams/mol

Mass of 10.5 moles = 10.5 * molar mass

Mass of 10.5 moles = 10.5 * 38

Mass = 399 grams

__________________________________________________________

<u>005</u><u> - Number of moles in 9.78 * 10²¹ formula units of CeI₃</u>

Number of Moles:

We have the formula:

Number of moles = Number of Formula units / 6.022* 10²³

replacing the variables

Number of Moles = 9.78 * 10²¹ / 6.022*10²³

Number of Moles = 1.6 / 10²

Number of Moles = 1.6 * 10⁻² moles   OR   0.016 moles

3 0
2 years ago
When the molecules of gases are heated, the average kinetic energy of the molecules increases,
serious [3.7K]
True is the answer to this
6 0
3 years ago
Sodium carbonate can be made by heating sodium bicarbonate: 2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g) At 25°C, for this reaction,
insens350 [35]

Answer:

401.17 K is the minimum temperature at which the reaction will become spontaneous under standard state conditions.

Explanation:

The expression for the standard change in free energy is:

\Delta G=\Delta H-T\times \Delta S

Where,  

\Delta G is the change in the Gibbs free energy.

T is the absolute temperature. (T in kelvins)

\Delta H is the enthalpy change of the reaction.

\Delta S is the change in entropy.

Given at:-

Temperature = 25.0 °C

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15  

So,  

T₁ = (25.0 + 273.15) K = 298.15 K

\Delta H = 128.9 kJ/mol

\Delta G = 33.1 kJ/mol

Applying in the above equation, we get as:-

33.1=128.9-298.15\times \Delta S

-29815\Delta S=-9580

\Delta S=-9580 = 0.32131 kJ/Kmol

So, For reaction to be spontaneous, \Delta G

Thus, For minimum temperature:-

\Delta H-T\times \Delta S=0

128.9-T\times 0.32131=0

T=\frac{128.9}{0.32131}=401.17\ K

<u>Hence, 401.17 K is the minimum temperature at which the reaction will become spontaneous under standard state conditions.</u>

6 0
2 years ago
1.
Lisa [10]

Answer: High Precision

Explanation: It's High Precision because it's not accurate but close to 40 degrees Celsius.

6 0
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The surface temperature on Venus may approach 753 K. What is this temperature in degrees Celsius?
Darya [45]

Answer:

461.85 degrees Celsius

7 0
3 years ago
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