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3 years ago

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13. How many protons are present in total in a carbon atom?

1 answer:

frutty [35]3 years ago

3 0

Answer:

The answer to your question is below

13.- b

Explanation:

13. How many protons are present in total in a carbon atom?

(a) There are always twelve. No, atomic mass of Carbon is 12 but the number of protons is half the atomic mass (6).

(b) There are always six. The answer is correct. Carbon's atomic number is 6, that means that it has 6 protons.

(c) It depends on the isotope. It's wrong, depends on the isotope the number of neutrons but not the number of protons.

(d) There are always four. No, 4 is the number of protons of Beryllium.

14. Of the following, which molecule is most polar? (The electronegativities of the atoms are as follows: chlorine 3.0, boron 2.0, hydrogen 2.1, oxygen 3.5, carbon 2.5, and bromine 2.8.)

Oxygen, because of these elements is the one with the highest electronegativity.

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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

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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 $SCN^-$ .

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

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

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

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The limiting reagent is, $SCN^-$

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

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

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

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

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