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4 years ago

Which of the following is not an indication of a chemical reaction?

Chemistry

1 answer:

eimsori [14]4 years ago

7 0

Answer: Option (3) is the correct answer.

Explanation:

A reaction due to which there occurs change in chemical composition of reactants is known as a chemical reaction.

For example, evolution of heat when two substances combine together shows a chemical reaction has taken place between the substances.

Whereas a reaction which does not bring any changes in chemical composition of the reactants is known as a physical reaction.

For example, boiling point, melting point, mass, volume etc are all physical properties.

Thus, we can conclude that out of the given options a substance melts when sitting in the Sun, is not an indication of a chemical reaction.

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A standard solution of FeSCN2+ is prepared by combining 9.0 mL of 0.20 M Fe(NO3)3 with 1.0 mL of 0.0020 M KSCN . The standard so

Xelga [282]

Answer : The equilibrium concentration of $SCN^-$ in the trial solution is $4.58\times 10^{-8}M$

Explanation :

First we have to calculate the initial moles of $Fe^{3+}$ and $SCN^-$ .

$\text{Moles of }Fe^{3+}=\text{Concentration of }Fe^{3+}\times \text{Volume of solution}$

$\text{Moles of }Fe^{3+}=0.20M\times 9.0mL=1.8mmol$

and,

$\text{Moles of }SCN^-=\text{Concentration of }SCN^-\times \text{Volume of solution}$

$\text{Moles of }SCN^-=0.0020M\times 1.0mL=0.0020mmol$

The given balanced chemical reaction is,

$Fe^{3+}(aq)+SCN^-(aq)\rightleftharpoons FeSCN^{2+}(aq)$

Since 1 mole of $Fe^{3+}$ reacts with 1 mole of $SCN^-$ to give 1 mole of $FeSCN^{2+}$

The limiting reagent is, $SCN^-$

So, the number of moles of $FeSCN^{2+}$ = 0.0020 mmole

Now we have to calculate the concentration of $FeSCN^{2+}$ .

$\text{Concentration of }FeSCN^{2+}=\frac{0.0020mmol}{9.0mL+1.0mL}=0.00020M$

Using Beer-Lambert's law :

$A=\epsilon \times C\times l$

where,

A = absorbance of solution

C = concentration of solution

l = path length

$\epsilon$ = molar absorptivity coefficient

$\epsilon$ and l are same for stock solution and dilute solution. So,

$\epsilon l=\frac{A}{C}=\frac{0.480}{0.00020M}=2400M^{-1}$

For trial solution:

The equilibrium concentration of $SCN^-$ is,

$[SCN^-]_{eqm}=[SCN^-]_{initial}-[FeSCN^{2+}]$

$[SCN^-]_{initial}$ = 0.00050 M

Now calculate the $[FeSCN^{2+}]$ .

$C=\frac{A}{\epsilon l}=\frac{0.220}{2400M^{-1}}=9.17\times 10^{-5}M$

Now calculate the concentration of $SCN^-$ .

$[SCN^-]_{eqm}=[SCN^-]_{initial}-[FeSCN^{2+}]$

$[SCN^-]_{eqm}=(0.00050M)-(9.17\times 10^{-5}M)$

$[SCN^-]_{eqm}=4.58\times 10^{-8}M$

Therefore, the equilibrium concentration of $SCN^-$ in the trial solution is $4.58\times 10^{-8}M$

5 0

4 years ago

Please select the word from the list that best fits the definition

AveGali [126]

Answer:

I choose D option because may be it's correct

3 0

3 years ago

Read 2 more answers

An atom has an average atomic mass of about 63.5 amu. What is the chemical symbol for the atom? Consult the periodic table.

Mama L [17]

The best and most correct answer among the choices provided by your question is the fourth choice.

Copper <span>has an average atomic mass of about 63.5 </span>amu<span>.</span>

I hope my answer has come to your help. Thank you for posting your question here in Brainly. We hope to answer more of your questions and inquiries soon. Have a nice day ahead!

8 0

4 years ago

Read 2 more answers

An empty erlenmeyer flask weighs 241.3 g. when filled with water (d = 1.00 g/cm3), the flask and its contents weigh 489.1 g. wha

g100num [7]

The volume of the flask would simply be equal to the volume of the water. And the mass of the water would be the difference after and before weigh.

mass of water = 489.1 g – 241.3 g

mass of water = 247.8 g

Therefore the volume of water (which is also the volume of the flask) is:

volume = 247.8 g / (1.00 g/cm^3)

volume = 247.8 cm^3

The total mass of the flash when filled with chloroform would be:

total mass with chloroform = 241.3 g + 247.8 cm^3 (1.48 g/cm3)

total mass with chloroform = 608.04 g

Answers:

volume = 247.8 cm^3

total mass with chloroform = 608.04 g

4 0

4 years ago

What is the density of a sample of the alloy pewter, (a mixture of tin and copper or lead) if a 7.11 cm3 sample has a mass of 53

xxTIMURxx [149]

Answer:

<h3>The answer is 7.47 g/cm³</h3>

Explanation:

The density of a substance can be found by using the formula

$density = \frac{mass}{volume} \\$

From the question

mass = 53.137 g

volume = 7.11 cm³

We have

$density = \frac{53.137}{7.11} \\ = 7.473558368...$

We have the final answer as

Hope this helps you

5 0

4 years ago