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3 years ago

List 4 observations that suggest a chemical change is occurring

2 answers:

8 0

1. Creation of different compounds. (Since a chemical change is one in which the arrangement of atoms changes.)
2. Color change. ( Because if a new compound is formed, its color can be different from the original compound)
3. Cannot be reversed by reversing the condition.
4. In most cases, a gas is formed.

BabaBlast [244]3 years ago

4 0

1. The evolution of energy
2. the production of a gas
3. the formation of a precipitate
4. color change

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Determine the number of atoms in 41.0 grams of calcium, Ca. (The mass of one mole of calcium is 40.08 g.)

Dovator [93]

Hi there!

Let me know if you have questions about my answer:

6.15 × 10²⁴

Explanation:

To find the number of atoms, divide the mass of calcium (m) by its molar mass (MM). This will give you the number of moles of calcium (n).

$n = m/MM$ Start with a formula

$=\frac{41.0g}{40.08g/mol}$ Substitute values from the question

$= \frac{41.0g*1mol}{40.08g}$ Simplify

$= \frac{41.0mol}{40.08}$ Cancel out the units "g"

$= 1.022...mol$ Number of moles of calcium, with 4 significant figures

Then, multiply the number of moles of calcium (n) by Avogadro's number ( $N_{A}$ ) to find the number of calcium atoms.

$Number.of.Ca=n*N_{A}$ Start with a formula

$= 1.022mol*\frac{6.022*10^{23}Ca}{1mol}$ Substitute values from the question

$= \frac{1.022mol*6.022*10^{23}Ca}{1mol}$ Simplify

$= 1.022*(6.022*10^{23}Ca)$ Cancel out the units "mol"

$= 6.154*10^{24} Ca$ Multiply, leave one extra digit to help round. "4" tells you to round down.

$= 6.15*10^{24} Ca$ Final answer to 3 significant figures*

*When multiplying and dividing numbers, your final answer will have the same number of significant figures as the number with the least number of significant figures in the question.

40.08 has 4 significant figures. 41.0 has 3 significant figures. So, you want 3 significant figures in your final answer.

I hope this helps!

Learn more about Avogadro's number here:

brainly.com/question/1445383

Check out another answer that uses significant figures:

brainly.com/question/3721164

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2 years ago

I NEED HELP ASAP!!!! ITS DUE IN A FEW MINUTES!!!!

OleMash [197]

Answer:

The Sun and the planets were born from a cloud of gas and dust called the solar nebula 4.6 billion years ago. The collapse of the solar nebula was most likely triggered by a shock wave from a nearby supernova explosion. The Sun formed in the center, with the planets surrounding it in a thin disk.

Explanation:

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2 years ago

What happens to air pressure as altitude increases

gulaghasi [49]

Answer:

the air pressure decreases

explanation

as altitude increases air pressure decreases the surface of the Earth is bottom of the ocean of the are the layer on top increase pressure so that sea levels a body is under 14.7 pounds of pressure per square inch moving up in altitude decreases weight of the air that causes the pressure

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3 years ago

The gasses in a hair spray can are at temperature 300k and a pressure of 30 atm, it

Sergeeva-Olga [200]

Answer:

900 K

Explanation:

Recall the ideal gas law:

$\displaystyle PV = nRT$

Because only pressure and temperature is changing, we can rearrange the equation as follows:
$\displaystyle \frac{P}{T} = \frac{nR}{V}$

The right-hand side stays constant. Therefore:

$\displaystyle \frac{P_1}{T_1} = \frac{P_2}{T_2}$

The can explodes at a pressure of 90 atm. The current temperature and pressure is 300 K and 30 atm, respectively.

Substitute and solve for T₂:

$\displaystyle \begin{aligned} \frac{(30\text{ atm})}{(300\text{ K})} & = \frac{(90\text{ atm})}{T_2} \\ \\ T_2 & = 900\text{ K}\end{aligned}$

Hence, the temperature must be reach 900 K.

7 0

2 years ago

How does an atom of one element differ from the atom of another element?

Temka [501]

Explanation:

The atoms of one element differs from the atoms of other elements in terms of the number of protons they contain. This is often taken as the atomic number of such an atom.

The number of proton is the best indicator of the atom one is dealing with.
Based on this number, elements are categorized into distinct columns and rows on the periodic table.
The atomic number is the number of protons or positively charge particles in the atom.

II.

It is possible to change the identity of an atom. This is only possible by altering the atomic number of the atom.

Only nuclear reactions have this capability.

When an atom undergoes nuclear reaction that involves change in number of protons, transmutation occurs and a new atom forms.

8 0

2 years ago