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3 years ago

Describe the difference between a chemical reaction and a physical change.

1 answer:

5 0

A chemical change results from a chemical reaction, while a physical change is when matter changes forms but not chemical identity.

Examples of chemical changes are burning, cooking, rusting, and rotting.

Examples of physical changes are boiling, melting, freezing, and shredding.

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4. The following occurs when heat energy is removed: Gas --A-> Liquid-B--> Solid.

Misha Larkins [42]

Answer: The phase change for A and B respectively is condensation, freezing.

Explanation:

A process in which gaseous state of a substance converts into liquid state is called condensation.

For example, conversion of steam into water.

A process in which liquid state of a substance converts into solid state is called freezing.

For example, conversion of liquid water into ice.

Thus, we can conclude that the phase change for A and B respectively is condensation and freezing.

6 0

3 years ago

In the laboratory, hydrogen gas is usually made by the following reaction: Zn(s) + 2 HCl(aq) → H2(g) + ZnCl2(aq) How many liters

IrinaK [193]

<u>Answer:</u> The volume of hydrogen gas collected over water is 2.13 L

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of zinc = 5.566 g

Molar mass of zinc = 65.4 g/mol

Putting values in above equation, we get:

$\text{Moles of zinc}=\frac{5.566g}{65.4g/mol}=0.0851mol$

For the given chemical reaction:

$Zn(s)+2HCl(aq.)\rightarrow H_2(g)+ZnCl_2(aq.)$

As, HCl is present in excess. So, it is considered as an excess reagent.

Zinc is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

1 mole of zinc produces 1 mole of hydrogen gas.

So, 0.0851 moles of zinc will produce = $\frac{1}[1}\times 0.0851=0.0851mol$ of hydrogen gas

To calculate the volume of hydrogen gas, we use ideal gas equation, which is:

PV = nRT

where,

P = Pressure of hydrogen gas = Total atmospheric pressure - vapor pressure of water = (752 - 18.65) mmHg = 733.35 mmHg

V = Volume of the hydrogen gas

n = number of moles of gas = 0.0851 moles

R = Gas constant = $62.3637\text{ L.mmHg }mol^{-1}K^{-1}$

T = Temperature of hydrogen gas = $21^oC=[21+273]K=294K$

Putting values in above equation, we get:

$733.35mmHg\times V=0.0851mol\times 62.3637\text{ L.mmHg }mol^{-1}K^{-1}\times 294K\\\\V=\frac{0.0851\times 62.3637\times 294}{733.35}=2.13L$

Hence, the volume of hydrogen gas collected over water is 2.13 L

5 0

3 years ago

A 55 kg person on Earth has the __________mass on the moon.

Semmy [17]

Answer:

89.1 N

Explanation:

W = m gm = 55.0 x 1.62 = 89.1 N

5 0

3 years ago

Someone help ,, I'll give brainliest lolll .

Darya [45]

The last option is correct

6 0

3 years ago

Read 2 more answers

Help me out hear i need help

____ [38]

Answer:

Explanation:

i cant see the attachment

6 0

3 years ago