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ziro4ka [17]
2 years ago
9

an atom has 79 protons, 78 electrons and a mass number of 118. how many neutrons does this atom have​

Chemistry
1 answer:
igomit [66]2 years ago
4 0

Answer:

39

Explanation:

Electrons weigh almost nothing, so their mass doesn't really matter for these types of problems. Just subtract 118-79 to find the remaining mass which is for the neutrons.

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Salt is often added to water to raise the boiling point to heat food more quickly. if you add 30.0g of salt to 3.75kg of water,
sammy [17]

Assuming an ebullioscopic constant of 0.512 °C/m for the water, If you add 30.0g of salt to 3.75kg of water, the boiling-point elevation will be 0.140 °C and the boiling-point of the solution will be 100.14 °C.

<h3>What is the boiling-point elevation?</h3>

Boiling-point elevation describes the phenomenon that the boiling point of a liquid will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent.

  • Step 1: Calculate the molality of the solution.

We will use the definition of molality.

b = mass solute / molar mass solute × kg solvent

b = 30.0 g / (58.44 g/mol) × 3.75 kg = 0.137 m

  • Step 2: Calculate the boiling-point elevation.

We will use the following expression.

ΔT = Kb × m × i

ΔT = 0.512 °C/m × 0.137 m × 2 = 0.140 °C

where

  • ΔT is the boiling-point elevation
  • Kb is the ebullioscopic constant.
  • b is the molality.
  • i is the Van't Hoff factor (i = 2 for NaCl).

The normal boiling-point for water is 100 °C. The boiling-point of the solution will be:

100 °C + 0.140 °C = 100.14 °C

Assuming an ebullioscopic constant of 0.512 °C/m for the water, If you add 30.0g of salt to 3.75kg of water, the boiling-point elevation will be 0.140 °C and the boiling-point of the solution will be 100.14 °C.

Learn more about boiling-point elevation here: brainly.com/question/4206205

7 0
2 years ago
How will the rate at which a solid solute dissolves change if the solution is stirred?
MakcuM [25]

Answer:

The rate at which the solute dissolves will increase.

Explanation:

If a solution is stirred, the rate at which a solute dissolves would increase substantially provided the solution is not yet saturated.

Stiring would cause more of the solution to come in contact with every part of the solute. It will increase the surface area of contact for the solution to act which will shoot up the rate of reaction. Stiring helps to bring solutes in solutions into a more close contact with the molecules or compounds of the medium.

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3 years ago
2.50 g CuCl2 equals how many moles
Vitek1552 [10]
The molar mass of CuCl2 is 134.45 g/mol; therefore, you divide 2.5 g of CuCl2 by 134.45 g of CuCl2 leaving you with 0.019 moles
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Give me 25 minutes and I’ll have the answers :)
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The American Council for an Energy Efficient Economy works to _______.
Komok [63]
<span>The American Council for an Energy-Efficient Economy works to (c) </span>invest in clean energy technologies that will strengthen the economy.

Their aim is to promote energy efficiency which will ultimately benefit the economy and the environment. 
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