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2 years ago

Please help thank you! And how many significant figures does it have?

Chemistry

1 answer:

zheka24 [161]2 years ago

6 0

Answer:

0.779 cube centimetres

Explanation:

density = mass divided by volume

$d=\frac{m}{v}$ rearrange the equation to solve for volume: $v=\frac{m}{d}$

plug in the corresponding values:

volume = 6.130 g / 7.87 (gcm^3)

the gs cancel, the answer will be 0.7789

we will round to three sig figs, since that's the lowest amount of figures in the given values: ~0.779 cm^3

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3 years ago

Potassium thiocyanate, KSCN, is often used to detect the presence of Fe3+ ions in solution through the formation of the red Fe(H

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Answer:

Ferric ions left in the solution at equilibrium is $8.0\times 10^{-6} M$ .

Explanation:

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$n=M\times V=0.00150 M\times 0.700 L=0.00105 mol$

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$n'=M'\times V'=0.200 M\times 0.700 L=0.140 mol$

Molarity of ferric ions after mixing :

1 mol of ferric nitrate gives 1 mol of ferric ions.Then 0.00105 mol ferric nitrate will :

Moles of ferric ions = 0.00105 mol

$M_1=\frac{0.00105 mol}{0.700 L+0.700 L}=0.00075 M$

Molarity of thiocyanate ions after mixing :

1 mol of potassium thiocyanate gives 1 mol of thiocyanate ions.Then 0.140 mol potassium thiocyanate will give:

Moles of thiocyanate ions = 0.140 mol

$M_2=\frac{0.140 mol}{0.700 L+0.700 L}=0.1 M$

Complex equation:

$Fe^{3+}+SCN^-\rightleftharpoons [Fe(SCN)]^{2+}$

0.00075 M 0.1 M 0

At equilibrium:

(0.00075 M -x) (0.1 M-x) x

The formation constant of the given complex = $K_f=8.9\times 10^2$

$K_f=\frac{[[Fe(SCN)]^{2+}]}{[[Fe^{3+}]][SCN^{-}]}$

$8.9\times 10^2=\frac{x}{(0.00075 M -x)\times (0.1 M-x)}$

Solving for x:

x = 0.000742 M

Ferric ions left in the solution at equilibrium :

= (0.00075 M -x) = (0.00075 M - 0.000742 M)= $8.0\times 10^{-6} M$

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2 years ago

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Evgesh-ka [11]

Answer:

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