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dezoksy [38]
2 years ago
15

Which one is a chemical reaction? Why?

Chemistry
1 answer:
Alex17521 [72]2 years ago
3 0

Answer:

Copper turns green on exposure to air

Explanation:

Liquid water freezes to form ice: Physical change

Reason: Water can melt back when it becomes ice.

Copper turns green on exposure to air: Chemical change

Reason: The copper can not change back from the green state when it turns green.

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For which of the following is heat energy absorbed?
Dvinal [7]
Your answer is sublimation.

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3 years ago
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Which of the following pieces of laboratory glassware should be used to most accurately measure out a 25.00 ml sample of a solut
wel

Answer:

The correct answer is 25 mL graduated cylinder (it should be used in all the cases)

Explanation:

In order to measure 25.00 ml sample of a solution it should be used a 25 mL graduated cylinder, as it is previously and properly calibrated. The other laboratory glassware, beaker and erlenmeyer, have graduations which are approximate, so they are used when exact volumes are not needed.

ii) graduated cylinder has the least uncertainly. It is more accurate than a beaker or erlenmeyer (to within 1%)

iii) A 25 mL graduated cylinder should be used because it is the most accurate lab glassware (between those were mentioned: beaker, erlenmeyer).

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3 years ago
Do substances react by mass? Yes or no explain
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yes substances Do  react by mass

5 0
3 years ago
What is the molar mass of Na2CO3? 60.0 g/mol 106.0 g/mol 118.0 g/mol 141.0 g/mol
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Answer is: the molar mass od sodium carbonate (Na₂CO₃) is 106.0 g/mol.

M(Na₂CO₃) = 2 · Ar(Na) + Ar(C) + 3 · Ar(O).

M(Na₂CO₃) = 2 · 23 + 12 + 3 · 16 · g/mol.

M(Na₂CO₃) = 46 + 12 + 48 · g/mol.

M(Na₂CO₃) = 106 g/mol; molar mass of sodium carbonate.

Ar is relative atomic mass (the ratio of the average mass of atoms of a chemical element to one unified atomic mass unit) of an element.

8 0
3 years ago
Metals present in municipal wastewater may still be present in treated sewage sludge; ______
Marrrta [24]
Metals present in municipal waste water may still be present in treated sewage sludge IN CONCENTRATIONS THAT MAY AFFECT THE PUBLIC HEALTH. Sewage sludge is an end product of municipal waste water treatment and it contains many of the pollutant that are removed from the waste water. 
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