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julia-pushkina [17]
4 years ago
10

Methods scientists use to determine if a change was physical or chemical.

Chemistry
2 answers:
Tpy6a [65]4 years ago
7 0
Chemical reactions can be identified when there is a change in color, energy is produced, change in odor, or if new substance forms.
alukav5142 [94]4 years ago
5 0
Chemical change can be determine by
change in color
energy
change in odor
rusting metal
wood burning
Physical change can be determine by
Ripping of paper
Sharpening of a pencil
Boiling of water
Melting an ice cube
Braking of glass

hope it helps



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How many molecules of sodium oxide will be created if 275 grams of sodium reacts with excess oxygen?
DaniilM [7]

Answer:

  • <em>1.34 × 10²⁴ molecules</em>

Explanation:

To calculate the <em>number of molecules of sodium oxide that will be created if 275 grams of sodium reacts with excess oxygen</em>, use the chemical equation to calculate the number of moles and then multiply by Avogadro's number.

<u>1) Balanced chemical equation (given):</u>

  • 4Na + O₂ → 2Na₂O

<u>2) Mole ratio:</u>

  • 4 mol Na : 2 mol Na₂O

<u>3) Calculate the number of moles in 275 g  of Na:</u>

  • n = mass in grams / molar mass
  • mass of Na = 275 g
  • molar mass of Na₂O = 61.9789 g/mol

  • n = 275 g / 61.9789 g/mol = 4.437 mol of Na

<u>4) Set a proportion to find the number of moles of product (Na₂O):</u>

  • 2 mol Na₂O / 4 mol Na = x / 4.437 mol Na

  • x = 4.437 /  2 mol Na₂O = 2.2185 mol Na₂O

<u>5) Convert the number of moles to number of molecules:</u>

  • # molecules = n × 6.022 × 10²³ molecules/mol = 2.2185 mol × 6.022 × 10²³ molecules/mol = 1.34 × 10²⁴ molecules (rounded to 3 significant figures).
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What organ is known as the windpipe and the tube takes in air ?
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Explanation:

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Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Thanks and I hope it helped.

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If in a redox reaction oxidation state of elements decreases or looses electron(s), the element is said to be oxidized. Hope this helps you!
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Which statement best describes how geothermal energy is made to make electricity?
Juli2301 [7.4K]

Answer:

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Explanation:

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