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OLEGan [10]
2 years ago
3

A coffee-cup calorimeter contains 130.0 g of water at 25.1 ∘C . A 121.0-g block of copper metal is heated to 100.4 ∘C by putting

it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g⋅K. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.2 ∘C . Determine the amount of heat, in J , lost by the copper block.
Chemistry
1 answer:
Blizzard [7]2 years ago
8 0

Answer:

The heat lost by the copper block is 3270 J

Explanation:

A coffee-cup calorimeter is an instrument used in chemistry to obtain values as enthalpy change (ΔH) or changes in internal energy (ΔU)

The equation of interest is:

Q = C×m×ΔT

Where:

Q is the amount of heat

C is specific heat (For Cu is 0,385 J/gK)

m is mass of copper (121,0g)

And ΔT is final temperature - initial temperature (30,2°C - 100,4°C)

Replacing:

Q = -3270 J

<em>The heat lost by the copper block is 3270 J</em>

<em></em>

I hope it helps!

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makvit [3.9K]

Answer:

There are necessaries 35,2g of NH₄NO₃ per 100,0g of water to decrease the temperature of the solution from 25,0°C to 5,0°C

Explanation:

To decrease the temperature of the solution there are necessaries:

4,184J/g°C×(5,0°C-25,0°C)×(100,0g+X) = -Y

8368J + 83,68J/gX = Y <em>(1)</em>

Where x are grams of NH₄NO₃ you need to add and Y is the energy that you need to decrease the heat.

Also, the energy Y will be:

Y = 25700J/mol×\frac{1mol}{80,043g}X

Y = 321J/g X <em>(2)</em>

Replacing (2) in (1)

8368J + 83,68J/g X = 321J/g X

8363J = 237,32J/gX

<em>X = 35,2g</em>

<em />

Thus, there are necessaries 35,2g of NH₄NO₃ per 100,0g of water to decrease the temperature of the solution from 25,0°C to 5,0°C

I hope it helps!

6 0
2 years ago
Consider the following incomplete reaction. Mg + 2Y ---&gt; MgCl₂ + H₂ Choose the formula for the missing substance Y.
vesna_86 [32]
It would be B as the answer
7 0
2 years ago
A 2135 cm3 sample of dry air has a pressure of 98.4 kpa at 127 degrees Celsius. What is the volume of the sample if the Temperat
kykrilka [37]

the equation is p1 x v1 divided by T1 = p1 x v2 = T2 but since the pressure is kept constant you do not even need it so the equation would now be v1 divided by t1 = v2 divided by t2

2135 cm3 divided by 127 degrees celcius = x divided by 206

answer: 3460 cm3

7 0
2 years ago
Read 2 more answers
Cyclohexane has a freezing point of 6.50 ∘C and a Kf of 20.0 ∘C/m. What is the freezing point of a solution made by dissolving 0
ExtremeBDS [4]

Answer:

The freezing point will be 2.9^{0}C

Explanation:

The depression in freezing point is a colligative property.

It is related to molality as:

Depressioninfreezing point=K_{f}Xmolality

Where

Kf= 20\frac{^{0}C}{m}

the molality is calculated as:

molality=\frac{moles_{solute}}{mass_{solvent}}

moles=\frac{mass}{molarmass}=\frac{0.694}{154}=0.0045mol

massofcyclohexane=25g=0.025Kg

molarity=\frac{0.0045}{0.025}=0.18m

Depression in freezing point = 20X0.18=3.6^{0}C

The new freezing point = 6.5^{0}C-3.6^{0}C=2.9^{0}C

5 0
2 years ago
An ice cube measuring 5.80 cm by 5.80 cm by 5.80 cm has a density of 0.917 g/mL What is the mass?
OLga [1]

Answer: 178.9 g

Explanation:

Density = \frac{mass}{volume in mL}

find volume of the cube: (5.80 cm) (5.80 cm) (5.80cm) = 195.112 cm³

1.0 cm³ = 1.0 mL

so 195.112 cm³ = 195.112 mL

plug value into density equation:

0.917 g/mL = (mass) / (195.112 mL)

and solve for mass!

3 0
2 years ago
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