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3 years ago

What is the energy change when 78.0 g of Hg melt at −38.8°C

Chemistry

1 answer:

adell [148]3 years ago

5 0

Answer:

The correct answer is - 2.557 KJ

Explanation:

In this case, Hg is melting, the process is endothermic, so the energy change will have a positive sign.

we can calculate this energy by the following formula:

Q = met

where, m = mass,

e = specific heat

t = temperature

then,

Q = 78*0.14* (273-38.8)

here 0.14 = C(Hg)

= 2.557 Kj

You might be interested in

Fill in the coefficients that will balance the following reaction:

vfiekz [6]

6NaC₂H₃O₂ + Fe₂O₃ → 2Fe(C₂H₃O₂)₃ + 3Na₂O

Explanation:

Given equation;

NaC₂H₃O₂ + Fe₂O₃ → Fe(C₂H₃O₂)₃ + Na₂O

To find the coefficient that will balance this we equation, let us set up simple mathematical algebraic expressions that we can readily solve.

Let us have at the back of our mind that, in every chemical reaction, the number of atom is usually conserved.

aNaC₂H₃O₂ + bFe₂O₃ → cFe(C₂H₃O₂)₃ + dNa₂O

a, b, c and d are the coefficients that will balance the equation.

conserving Na; a = 2d

C: 2a = 6c

H: 3a = 9c

O; 2a + 3b = 6c + d

Fe: 2b = c

let a = 1

solving:

2a = 6c

2(1) = 6c

c = $\frac{2}{6} = \frac{1}{3}$

2b = c

b = $\frac{1}{2} x \frac{1}{3}$ = $\frac{1}{6}$

d = 2a + 3b - 6c = 2(1 ) + (3 x $\frac{1}{6}$ ) - (6 x $\frac{1}{3}$ ) = $\frac{1}{2}$

Now multiply through by 6

a = 6, b = 1, c = 2 and d = 3

6NaC₂H₃O₂ + Fe₂O₃ → 2Fe(C₂H₃O₂)₃ + 3Na₂O

learn more:

Balanced equation brainly.com/question/9325293

#learnwithBrainly

6 0

3 years ago

Which observations is the best evidence that unknown liquid X is a composed of only pure substance

Angelina_Jolie [31]

Answer:

A substance that is composed only of atoms having the same atomic number is ... 36 grams of an unknown liquid at its boiling point,.

4 0

3 years ago

The majority of energy used in industrialized countries is produced using renewable resources.

vaieri [72.5K]

Answer:

The answer is FALSE

Explanation:

I took the test and it was false,

also if it was true then in industrialized countries would be more eco-friendly and there wouldn't be a huge hole in our ozone layer. and no more wars over oil.

7 0

3 years ago

Which cohesive forces are the strongest in water?

jeyben [28]

When cohesive force is stronger than the adhesive force: concave up meniscus, water forms droplets on surface

4 0

3 years ago

Olympic cyclists fill their tires with helium to make them lighter. Assume that the volume of the tire is 860 mL , that it is fi

nata0808 [166]

Answer:

a) the mass of air = 8.24 grams

b) the mass of helium = 1.14 grams

c) the mass difference = 7.10 grams

Explanation:

Step 1: Data given

Volume of the tire = 860 mL

Total pressure = 120 psi

Temperature = 26°C

molar mass of air = 28.8 g/mol

Step 2: Convert psi to atm

(

120 psi) (1 atm / 14.7 psi) = 8.163

Step 4: Calculate moles

PV = nRT

⇒ with P = the pressure = 8.163 atm

⇒ with V = the volume = 860 mL = 0.860 L

⇒ with n = the number of moles = TO BE DETERMINED

⇒ with R = the universal gas constant = 0.08206 L*atm/K*mol

⇒ with T = the temperature = 26 °C = 299 Kelvin

n = (8163*0.860)/(0.08206*299)

n = 0.2861 moles of gas

Step 5: Calculate the mass of air in an air-filled tire.

Mass = moles * molar mass

Mass = (0.2861 moles of gas) (28.8 g/mol)

Mass = 8.24 grams

Step 6: Calculate the mass of helium in a helium- filled tire.

mass of helium = 0.2861 moles of gas * 4 g/mol)

mass of helium = 1.14 grams

Step 7: What is the mass difference between the two?

Δmass= 8.24 grams - 1.14 grams

Δmass= 7.10 grams

8 0

3 years ago