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Feliz [49]
3 years ago
7

Calculate the number of atoms in 2.5 moles of Si.

Chemistry
1 answer:
Ede4ka [16]3 years ago
7 0

Answer:

\boxed {\boxed {\sf About \ 1.5 * 10^{24} \ atoms \ Si}}

Explanation:

When converting from moles to atoms, we must use Avogadro's number. This number tells us there are 6.022 * 10²³ atoms in 1 mole. We can multiply this number by the number of moles.

First, we must set up Avogadro's number as a ratio.

\frac {6.022 \ * 10^{23} \ atoms \ Si }{1 \ mol \ Si}}

Next, multiply the number of moles by the ratio.

2.5 \ mol \ Si *\frac {6.022 \ * 10^{23} \ atoms \ Si }{1 \ mol \ Si}}

When we multiply, the moles of silicon will cancel.

2.5 * \frac {6.022 \ * 10^{23} \ atoms \ Si }{1}}

Since the denominator of the fraction is 1, we can cancel it out too.

2.5 *  {6.022 \ * 10^{23} \ atoms \ Si }

1.5055 * 10^{24} \ atoms \ Si

The original measurement (2.5 moles) has 2 significant figures (2 and 5). Therefore we must round to 2 sig figs. For this question, 2 sig figs is the tenth place.

The 0 in the hundredth place tells us to leave the 5 in the tenth place.

1.5 * 10^{24} \ atoms \ Si

There are about <u>1.5 * 10²⁴ atoms of silicon.</u>

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3 years ago
Why is Newton's first law of motion important to science?
Lyrx [107]

Answer:

Newton's laws are very important because they tie into almost everything we see in everyday life. These laws tell us exactly how things move or sit still, like why you don't float out of bed or fall through the floor of your house.

Explanation: Newton's laws of motion are important because they are the foundation of classical mechanics, one of the main branches of physics. Mechanics is the study of how objects move or do not move when forces act upon them.

6 0
3 years ago
What is the specific heat capacity of an unknown metal if 75.00 g of the metal absorbs 418.6J of heat and the temperature rises
EleoNora [17]

Answer:

The specific heat capacity of the unknown metal is 0.223 \frac{J}{g*C}

Explanation:

Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.

There is a direct proportional relationship between heat and temperature. The constant of proportionality depends on the substance that constitutes the body as on its mass, and is the product of the specific heat by the mass of the body. So, the equation that allows calculating heat exchanges is:

Q = c * m * ΔT

where Q is the heat exchanged by a body of mass m, made up of a specific heat substance c and where ΔT is the temperature variation.

In this case, you know:

  • Q= 418.6 J
  • c= ?  
  • m= 75 g
  • ΔT= 25 C

Replacing:

418.6 J= c* 75 g* 25 C

Solving:

c=\frac{418.6 J}{75 g*25 C}

c= 0.223 \frac{J}{g*C}

<u><em>The specific heat capacity of the unknown metal is 0.223 </em></u>\frac{J}{g*C}<u><em></em></u>

<u><em> </em></u>

<u><em></em></u>

3 0
2 years ago
What is the percent composition of aluminum in the ore bauxite (AI2O3)?
Schach [20]

Answer:

Molar mass of Al2O3 = 101.961276 g/mol

This compound is also known as Aluminium Oxide.

Convert grams Al2O3 to moles or moles Al2O3 to grams

Molecular weight calculation:

26.981538*2 + 15.9994*3

Percent composition by element

Element Symbol Atomic Mass # of Atoms Mass Percent

Aluminium Al 26.981538 2 52.925%

Oxygen O 15.9994 3 47.075%

Explanation:

Percent composition by element

Element Symbol Mass Percent

Aluminium Al 52.925%

Oxygen O 47.075%

6 0
3 years ago
What is the bohr model for pottasium
guapka [62]
Potassium is an alkali metal with the chemical symbol K. It has an atomic number of 19, meaning that it has 19 positively charged protons. It also contains 19 electrons, which have a negative charge, and 20 neutrons, which do not hold a charge
Hope this help
7 0
3 years ago
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