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Vikentia [17]
3 years ago
11

Are phase changes physical or chemical changes? why?

Chemistry
2 answers:
Studentka2010 [4]3 years ago
6 0
Physical! Because they do not modify the nature of the substance ( if you look at the chemical level) and it is reversible

Vapor is H20
Water is H20
Ice is H20

A chemical changes is not reversible
Burning wood for example! And the reactants interact together to form a new product.
Reptile [31]3 years ago
3 0
<h2>Answer:</h2>

Physical changes

<h2>Example:</h2>

You added enough energy to create a phase change from solid to liquid. Physical actions, such as changing temperature or pressure, can cause physical changes. No chemical changes took place when you melted the ice. The water molecules are still water molecules.

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An isotope of cesium has 55 protons and 78 neutrons. What is the mass number of this isotope?
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What is the best name for the molecule below?
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3 years ago
You are given solutions of hcl and naoh and must determine their concentrations. you use 27.5 ml of naoh to titrate 100.0 ml of
Dafna1 [17]
1) Start by standardizing the solution of NaOH by using the solution of H2SO4 whose concentration is known.

2) Equation:

2Na OH + H2SO4 --> Na2 SO4 + 2H2O

3) molar ratios

2 mol NaOH : 1 mol H2SO4

4) Number of moles of H2SO4 in 50.0 ml of 0.0782 M solution

M = n / V => n = M*V = 0.0782 M * 0.050 l = 0.00391 mol H2SO4

5) Number of moles of NaOH

2 moles NaOH / 1mol H2SO4 * 0.00391 mol H2SO4 = 0.00782 mol NaOH

6) Concentration of the solution of NaOH

M = n / V = 0.00782 mol / 0.0184 ml = 0.425 M

7) Standardize the solution of HCl

Chemical reaction:

NaOH + HCl --> NaCl + H2O

8) Molar ratios

1 mol NaOH : 1 mol HCl

9) Number of moles of NaOH in 27.5 ml

M = n / V => n = M * V = 0.425 M * 0.0275 l = 0.01169 moles NaOH

10) Number of moles of HCl

1 mol HCl / 1mol NaOH * 0.01169 mol NaOH = 0.01169 mol HCl

11) Concentration of the solution of HCl

M = n / V = 0.01169 mol / 0.100 l = 0.1169 M

Rounded to 3 significant figures = 0.117 M

Answers:

[NaOH] = 0.425 M
[HCl] = 0.117 M
3 0
3 years ago
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Andrej [43]
I need this also I’m just here for points
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