2 years ago

How many significant numbers are there in 40.00

Chemistry

2 answers:

lesantik [10]2 years ago

6 0

4 because the zero is “captured” and any zero behind a (.) is a significant number

muminat2 years ago

3 0

The answer to this is 4.

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The chemical reaction 2Cu + O2 → 2CuO + 315 kJ is an _____ reaction. Endothermic, combustion Exothermic, combustion Endothermic,

makvit [3.9K]

the awnser is exothermic (combustion)

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3 years ago

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An iron ore sample weighing 0.5562 g is dissolved HCl (aq), and the iron is obtained as Fe2 in solution. This solution is then t

erik [133]

Answer:

$\% Fe^{+2}=70%$

Explanation:

Hello,

In this case, we could considering this as a redox titration:

$Fe^{+2}+(Cr_2O_7)^{-2}\rightarrow Fe^{+3}+Cr^{+3}$

Thus, the balance turns out (by adding both hydrogen ions and water):

$Fe^{+2}\rightarrow Fe^{+3}+1e^-\\(Cr_2^{+6}O_7)^{-2}+14H^++6e^-\rightarrow 2Cr^{+3}+7H_2O\\\\6Fe^{+2}+(Cr_2^{+6}O_7)^{-2}+14H^++6e^-\rightarrow Cr^{+3}+7H_2O+6Fe^{+3}+6e^-$

Thus, by stoichiometry, the grams of Fe+2 ions result:

$m_{Fe^{+2}}=0.04021\frac{molK_2Cr_2O_7}{L}*0.02872L*\frac{6molFe^{+2}}{1molK_2Cr_2O_7}*\frac{56gFe^{+2}}{1molFe^{+2}}=0.388gFe^{+2}$

Finally, the mass percent is:

$\% Fe^{+2}=\frac{0.388g}{0.5562g}*100\%\\ \% Fe^{+2}=70%$

Best regards.

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2 years ago

If the pH of a solution is 5, what is the hydrogen ion concentration?

Gnoma [55]

Yo sup??

We know that

pH=-log[H+]

[H+]=10^(-pH)

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therefore

[H+]=10^(-5)

The medium is acidic

Hope this helps.

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Explanation:

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