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frutty [35]
3 years ago
8

A compound is 40.0% c, 6.70% h, and 53.3% o by mass. assume that we have a 100.-g sample of this compound. the molecular formula

mass of this compound is 240 amu . what are the subscripts in the actual molecular formula?
Chemistry
1 answer:
atroni [7]3 years ago
3 0
<span>When you have 100 g of compound, then based on the percentages given, there are 40.0 g C, 6.70 g H, and 53.3 g O. Convert those to moles:

</span>C: 40.0 g / 12.0 = 3.33 moles of C 
<span>H: 6.70 g / 1.01 = 6.63 moles of H </span>
<span>O: 53.3 / 16.0 = 3.33 moles of O 
</span>
<span>Dividing by the smallest (3.33), we get a C:H:O mole ratio of 1:2:1
</span>So, <span>The empirical formula is CH2O.
Now, </span><span>That formula has a molar mass of [12.0 + 2(1.0) + 16.0] = 30.0

And we are given it's molar mass is = 240

So, no. of units of CH2O = 240 / 30 = 8

</span><span>8 x CH2O = C8H16O8, and that is the molecular formula.
</span>
C_8H_{16}O_8
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A solution is prepared by adding 0.700 g of solid NaClNaCl to 50.0 mL of 0.100 M CaCl2CaCl2. What is the molarity of chloride io
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Explanation :

First we have to calculate the mole of NaCl and CaCl_2.

\text{Moles of }NaCl=\frac{\text{Mass of }NaCl}{\text{Molar mass of }NaCl}

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\text{Moles of }CaCl_2=\text{Concentration of }CaCl_2\times \text{Volume of solution}

\text{Moles of }CaCl_2=0.100M\times 0.050L=0.005mol

Now we have to calculate the moles of chloride ion.

As, 1 mole of NaCl dissociates to give 1 mole of sodium ion and 1 mole of chloride ion.

So, 0.0118 mole of NaCl dissociates to give 0.0118 mole of sodium ion and 0.0118 mole of chloride ion.

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As, 1 mole of CaCl_2 dissociates to give 1 mole of sodium ion and 2 mole of chloride ion.

So, 0.005 mole of CaCl_2 dissociates to give 0.005 mole of sodium ion and (2×0.005=0.01) mole of chloride ion.

Now we have to calculate the total moles of chloride ion and volume of solution.

Total moles of chloride ion = 0.0118 + 0.01 = 0.0218 mol

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Now we have to calculate the molarity of chloride ion in the final solution.

\text{Molarity}=\frac{\text{Total moles}}{\text{Total volume}}

\text{Molarity}=\frac{0.0218mol}{0.050L}=0.436M

Thus, the molarity of chloride ion in the final solution is, 0.436 M

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