I need help pls this isnt chemistry btw i just couldnt find science so i had to put that

klio [65]

Answer:

There are 1.393 x 10²⁴ atoms in 25.00 g of B.

Explanation:

Hey there!

We are given a value, in grams, that we need to convert to a number of atoms.

We can convert grams to atoms by using Avogadro's Number ( $N_A$ ). This number is equivalent to $6.022 \times 10^{23}$ .

This number can be used to convert any values to:

atoms
molecules
formula units
moles

In order to do this problem, we will need to use dimensional analysis (DA). This process allows us to convert from grams to atoms.

We need to set up our ratios in order to work this out. We can use a periodic table to help us through this next part of the problem.

<u>1. Locating the number of moles of B in the sample</u>

We first need to find the amount of moles of boron (B) there are in the sample.

Checking a periodic table, the atomic mass in atomic mass units (amu) is 10.81 amu.

Atomic mass units can easily be converted to grams and these units can be used interchangeably.

Therefore, for each atom of boron, it weighs 10.81 grams to us. This is equivalent to the mass of one mole of boron.

To find the number of moles, we have two possible ratios we can use:

$\displaystyle \frac{1 \ mole \ B}{10.81 \ grams \ B}$

$\displaystyle \frac{10.81 \ grams \ B}{1 \ mole \ B}$

These ratios mean the same thing, but we need to convert our final unit to moles.

We are given a sample in grams, and when dividing our units, we need to keep moles.

Since the first portion of our expression is in grams, we need to have grams in the bottom of our expression.

$\displaystyle 25.00 \ \text{grams B} \ \times \frac{1 \text{mole B}}{10.81 \ \text{grams B}}$

We can now simplify the expression. Our <u>grams B</u> unit will cancel out, so we are therefore left with <u>moles B</u> remaining.

<u>2. Locating the number of atoms in the sample</u>

Now with our equation, we can convert our number of moles that would be solved if we stopped with the above. However, we need to convert to atoms.

We use Avogadro's number and create a ratio with that of moles.

$\displaystyle \frac{6.022 \times 10^{23}\text{atoms}}{1 \text{mole B}}$

$\displaystyle \frac{1 \text{mole B}}{6.022 \times 10^{23} \text{atoms}}$

We need to cancel out our moles and end with atoms, so we must have moles in the denominator. Therefore, we use the first ratio.

Using our previous expression, we multiply by this new ratio and solve the expression.

$\displaystyle 25.00 \ \text{grams B} \ \times \frac{1 \text{mole B}}{10.81 \ \text{grams B}} \ \times \frac{6.022 \times 10^{23}\text{atoms}}{1 \text{mole B}}$

This expression can now be operated. You will need a calculator to perform this calculation.

<u>Our numerator is:</u>

$[(25.00 \times 1 \times (6.022 \times 10^{23})]$

Plugging this into a calculator, we get:

$1.5055 \times 10^{25}$

<u>Our denominator is:</u>

$(1 \times 10.81 \times 1)$

This simplifies to:

$10.81$

<u>Dividing our numerator and denominator:</u>

<u /> $\displaystyle \frac{1.5055 \times 10^{25}}{10.81}$ <u />

Plugging this into a calculator, we get:

$1.392691952 \times 10^{24}$

<u>3. Simplifying with significant figures</u>

Now, we need to take into account that we have significant figures. We are given this original value:

$25.00$

This value has four significant figures, which means we need to round our value we received above to four significant figures.

$\approx 1.393$

Our units are added as well as our scientific notation:

$1.393 \times 10^{24} \ \text{atoms of B}$

Therefore, our final answer is choice A.

8 0

2 years ago

In the reaction 2 H2 + O2m 2 H20, how

Tresset [83]

Answer:

Option F. 3moles

Explanation:

The equation for the reaction is given below:

2H2 + O2 —> 2H2O

from the equation,

2moles of H2 required 1mole of O2.

Therefore, 6moles of H2 will require = 6/2 = 3moles of O2

8 0

3 years ago

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A 200. gram sample of a salt solution contains 0.050 grams of NaCl. What is the concentration of the

wariber [46]

Answer:

2.5 × 10² ppm

Explanation:

Step 1: Given data

Mass of NaCl: 0.050 g

Mass of the sample: 200. g

Step 2: Convert 0.050 g to μg

We will use the conversion factor 1 g = 10⁶ μg.

0.050 g × 10⁶ μg/1 g = 5.0 × 10⁴ μg

Step 3: Calculate the concentration of NaCl in ppm

The concentration of NaCl in ppm is equal to the micrograms of NaCl per gram of the sample.

5.0 × 10⁴ μg NaCl/200. g = 2.5 × 10² ppm

3 0

2 years ago

When a solute is added to a solution why does it remain homogeneous?

Olenka [21]

<h3>Answer:</h3>

When a solute is added to a solution, it remains homogeneous because the solute is soluble in given solvent.

<h3>Explanation:</h3>

Homogeneous mixtures, also called true solutions are those mixtures in which the components proportions are same throughout in any given sample. For example, the mixture of table salt (NaCl) and water. When the solution is unsaturated and further NaCl is added to it, it will dissolve the NaCl because the saturation point is still not reached. Remember, as "<em>Like Dissolves Like</em>" NaCl being polar in nature will interact with water molecules and will dissociate into Na⁺ and Cl⁻ ions surrounded by δ- O and δ+ H atoms of water molecules.

<h3>Conclusion:</h3>

In order to form a Homogeneous mixture the solution must be unsaturated, solvent must have affinity for incoming solute particles and the size of solute should be equal to 1 Â (Angstrom).

8 0

3 years ago

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Which law states that the entropy of the universe is always increasing?

vova2212 [387]

Second law of thermodynamics states entropy of the universe is always increasing. entropy always increases in a spontaneous process .

option B) second law of thermodynamics

for example if we keep a hot cup of coffee the heat is lost to surrounding and entropy( randomness increases) since it is a natural process entropy of universe increases.

5 0

2 years ago

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