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2 years ago

Please explain how we judge the brightness of stars.

1 answer:

6 0

Astronomers can measure it by way of luminosity which is the power of a star or the amount of energy (light) the star admits from its surface. they also measure the brightness of a start as if it were to appear 32.6 light years from Earth

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14. What are the different types of river in Nepal ?explain them briefly

Stella [2.4K]

Answer:

Explanation:

8 0

2 years ago

PLZZZZZZZ HELP MEEEEEE!!!!!!!!!!

nikitadnepr [17]

Answer:

Its Obviously Dinosaurs

Explanation: They died 65 million years ago

7 0

2 years ago

Use bond energies to calculate the enthalpy of reaction for the combustion of ethane. Average bond energies in kJ/mol C-C 347, C

ivanzaharov [21]

The enthalpy of reaction for the combustion of ethane 2CH₃CH₃ + 7O₂ → 4CO₂ + 6H₂O calculated from the average bond energies of the compounds is -2860 kJ/mol.

The reaction is:

2CH₃CH₃ + 7O₂ → 4CO₂ + 6H₂O (1)

The enthalpy of reaction (1) is given by:

$\Delta H = \Delta H_{r} - \Delta H_{p}$ (2)

Where:

r: is for reactants

p: is for products

The bonds of the compounds of reaction (1) are:

2CH₃CH₃: 2 moles of 6 C-H bonds + 2 moles of 1 C-C bond

7O₂: 7 moles of 1 O=O bond

4CO₂: 4 moles of 2 C=O bonds

6H₂O: 6 moles of 2 H-O bonds

Hence, the enthalpy of reaction (1) is (eq 2):

$\Delta H = \Delta H_{r} - \Delta H_{p}$

$\Delta H = 2*\Delta H_{CH_{3}CH_{3}} + 7\Delta H_{O_{2}} - (4*\Delta H_{CO_{2}} + 6*\Delta H_{H_{2}O})$

$\Delta H = 2*(6*\Delta H_{C-H} + \Delta H_{C-C}) + 7\Delta H_{O=O} - (4*2*\Delta H_{C=O} + 6*2*\Delta H_{H-O})$

$\Delta H = [2*(6*413 + 347) + 7*498 - (4*2*799 + 6*2*467)] kJ/mol$

$\Delta H = -2860 kJ/mol$

Therefore, the enthalpy of reaction for the combustion of ethane is -2860 kJ/mol.

I hope it helps you!

7 0

2 years ago

How many grams of FeCl 3 are in 250. mL of a 0.100 M solution?

Naddika [18.5K]

Answer:

The correct answer is option B

Explanation:

$$Molarity=\frac{Weight}{Molecular \,weight} \frac{1000}{V(in \, ml)}$

Given values,

Molarity of $FeCl_3=0.100M$

Volume of solution, $V=250ml$

Molecular weight of $FeCl_3=162.2$

Substituting this values in Molarity formula, we get

$0.1=\frac{weight}{162.2} \times\frac{1000}{250} $\\$\Rightarrow 16.22=weight\times4$\\$\Rightarrow weight=\frac{16.22}{4} $\\$\therefore weight=4.06g$

5 0

3 years ago

What is the name of a solution whose concentration of solute is equal to the maximum concentration that is predicted from the so

faltersainse [42]

<u>Answer:</u> The correct answer is saturated solution.

<u>Explanation:</u>

For the given options:

Dilute solutions are defined as the solutions in which solute particles are present in less very amount than the solvent particles.

Unsaturated solutions are defined as the solutions where more and more of solute particles can be dissolved in the given amount of solvent.

Saturated solutions are defined as the solutions where no more solute particles can be dissolved in the solvent. The concentration of the solute particles that can be dissolved in a solution is maximum.

Supersaturated solutions are defined as the solutions where more amount of solute particles are present than the solvent particles.

From the above information, we conclude that the given solution is saturated solution.

7 0

2 years ago

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