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3 years ago

What happens to iron when it melts?

Chemistry

2 answers:

den301095 [7]3 years ago

6 0

Answer:

B. It undergoes a physical change.

Explanation:

At room temperature, the iron atoms are in an unusual loosely packed open arrangement; as iron is heated past 912 degrees Celsius, the atoms become more closely packed before loosening again at 1,394 degrees Celsius and ultimately melting at 1,538 degrees Celsius.

iren [92.7K]3 years ago

5 0

Answer:

B. It undergoes a physical change.

Explanation:

Hello there!

In this case, since we know that chemical changes lead to the formation of new atoms and/or compounds due to the bonds rearrangement of the initial substances and the physical changes occur without changing the composition of the initial substances, we can infer that, since melting is a process that changes the phase of matter from solid to liquid without changing the identity of the initial substance, the answer to this question would be B. It undergoes a physical change. because the other options describe chemical changes.

Best regards!

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When 100.g Mg3N2 reacts with 75.0 g H2O, what is the maximum theoretical yield of NH3?

Temka [501]

Answer : The correct option is, 23.6 g

Explanation : Given,

Mass of $Mg_3N_2$ = 100.0 g

Mass of $H_2O$ = 75.0 g

Molar mass of $Mg_3N_2$ = 101 g/mol

Molar mass of $H_2O$ = 18 g/mol

First we have to calculate the moles of $Mg_3N_2$ and $H_2O$ .

$\text{Moles of }Mg_3N_2=\frac{\text{Given mass }Mg_3N_2}{\text{Molar mass }Mg_3N_2}$

$\text{Moles of }Mg_3N_2=\frac{100.0g}{101g/mol}=0.990mol$

and,

$\text{Moles of }H_2O=\frac{\text{Given mass }H_2O}{\text{Molar mass }H_2O}$

$\text{Moles of }H_2O=\frac{75.0g}{18g/mol}=4.17mol$

Now we have to calculate the limiting and excess reagent.

The balanced chemical equation is:

$Mg_3N_2(s)+6H_2O(l)\rightarrow 3Mg(OH)_2(aq)+2NH_3(g)$

From the balanced reaction we conclude that

As, 6 moles of $H_2O$ react with 1 mole of $Mg_3N_2$

So, 4.17 moles of $H_2O$ react with $\frac{4.17}{6}=0.695$ moles of $Mg_3N_2$

From this we conclude that, $Mg_3N_2$ is an excess reagent because the given moles are greater than the required moles and $H_2O$ is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of $NH_3$

From the reaction, we conclude that

As, 6 moles of $H_2O$ react to give 2 moles of $NH_3$

So, 4.17 moles of $H_2O$ react to give $\frac{2}{6}\times 4.17=1.39$ mole of $NH_3$

Now we have to calculate the mass of $NH_3$

$\text{ Mass of }NH_3=\text{ Moles of }NH_3\times \text{ Molar mass of }NH_3$

Molar mass of $NH_3$ = 17 g/mole

$\text{ Mass of }NH_3=(1.39moles)\times (17g/mole)=23.6g$

Therefore, the maximum theoretical yield of $NH_3$ is, 23.6 grams.

4 0

3 years ago

On the basis of le chatelier's principle explain why ag2co3 dissolves when hno3 is added

Bogdan [553]

The reaction is an equilibrium represented by the equation

<span>Ag2CO3(s) + 2 HNO3(aq) <----> 2 AgNO3(aq) + H2O(l) + CO2(g) </span>

From the <span>Le Chatelier's Principle which </span>states that changing a factor such as concentration, temperature, or pressure of a reaction at equilibrium will cause the reaction to shift in the direction that counteracts the effect of that change.
Therefore; the CO2 produced starts escaping and the concentration and pressure of CO2 drops. The system responds by trying to increase the concentration and pressure of CO2 by producing more. This means more and more Ag2CO3 will dissolve due to reaction with the acid, HNO3.
This continues until one of the reactants is exhausted.

7 0

3 years ago

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How many silver atoms are there in 3.78g of silver?

oksian1 [2.3K]

2.1 x 10²²atoms

Explanation:

Given parameters:

Mass of silver = 3.78g

Unknown:

Number of atoms of silver = ?

Solution:

To solve this problem, we first find the number of moles of the silver from the given mass.

Number of moles = $\frac{Mass}{Molar mass}$

Molar mass of Ag = 108g/mole

Number of moles = $\frac{3.78}{108}$ = 0.035mole

Now;

A mole of any substance contains 6.02 x 10²³ atoms

0.035 moles of Ag will contain 0.035 x 6.02 x 10²³ = 2.1 x 10²²atoms

learn more:

Number of moles brainly.com/question/13064292

#learnwithBrainly

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BartSMP [9]

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How do you do d the power of magnification on a microscope

Lemur [1.5K]

Answer: To figure the total magnification of an image that you are viewing through the microscope is really quite simple. To get the total magnification take the power of the objective (4X, 10X, 40x) and multiply by the power of the eyepiece, usually 10X.

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4 years ago

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