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3 years ago

How many molecules are in 79g of fe2o3

1 answer:

7 0

Convert grams —> mols and then mols —> atoms

We know that there are 6.02 x 10^23 atoms/mol

And we know that there are about 160 grams of fe2o3 per mol

So (79g fe2o3)/(160 g/mol) = .49 mol fe2o3

Now we use avogadro’s number to do

(.49 mol fe2o3)/(6.02 x 10^23 atoms/mol) = the answer.

I’ll leave the easy math to you.

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A student dissolved 5.00 g of Co(NO3)2 in enough water to make 100. mL of stock solution. He took 4.00 mL of the stock solution

Marianna [84]

Answer:

0.136g

Explanation:

A student dissolved 5.00 g of Co(NO3)2 in enough water to make 100. mL of stock solution. He took 4.00 mL of the stock solution and then diluted it with water to give 275. mL of a final solution. How many grams of NO3- ion are there in the final solution?

$Co(NO_3)_2(aq)\rightarrow Co^{2+}(aq)+2NO_3^{-}(aq)$

Initial mole of Co(NO3)2 $=\frac{mass}{molar mass}$

$=\frac{5.00}{182.94} \\\\=0.02733mol$

Mole of Co(NO3)2 in final solution

$=\frac{4.00}{100}\times 0.02733\\\\=0.04\times 0.02733\\\\= 0.001093mol$

Mole of NO3- in final solution = 2 x Mole of Co(NO3)2

$=2\times 0.001093\\\\=0.002186mol$

Mass of NO3- in final solution is mole x Molar mass of NO3

$=0.002186\times62.01\\\\=0.136g$

6 0

3 years ago

What is the molarity of formaldehyde in a solution containing 0.25 grams of formaldehyde per mL?

Vikentia [17]

Answer:

8.33mol/L

Explanation:

First, let us calculate the molar mass of of formaldehyde (CH2O). This is illustrated below:

Molar Mass of CH2O = 12 + (2x1) + 16 = 12 + 2 + 16 = 30g/mol

Mass of CH2O from the question = 0.25g

Number of mole CH2O =?

Number of mole = Mass /Molar Mass

Number of mole of CH2O = 0.25/30 = 8.33x10^-3mole

Now we can calculate the molarity of formaldehyde (CH2O) as follow:

Number of mole of CH2O = 8.33x10^-3mole

Volume = 1mL

Converting 1mL to L, we have:

1000mL = 1L

Therefore 1mL = 1/1000 = 1x10^-3L

Molarity =?

Molarity = mole /Volume

Molarity = 8.33x10^-3mole/1x10^-3L

Molarity = 8.33mol/L

Therefore, the molarity of formaldehyde (CH2O) is 8.33mol/L

3 0

3 years ago

What is the percent ionization of a 1.8 M HC2H3O2 solution (Ka = 1.8 10-5 ) at 25°C?

xz_007 [3.2K]

Answer:

B) 0.32 %

Explanation:

Given that:

$K_{a}=1.8\times 10^{-5}$

Concentration = 1.8 M

Considering the ICE table for the dissociation of acid as:-

$\begin{matrix}&CH_3COOH&\rightleftharpoons &CH_3COOH&+&H^+\\ At\ time, t = 0 &1.8&&0&&0\\At\ time, t=t_{eq}&-x&&+x&&+x\\ ----------------&-----&-&-----&-&-----\\Concentration\ at\ equilibrium:-&1.8-x&&x&&x\end{matrix}$

The expression for dissociation constant of acid is:

$K_{a}=\frac {\left [ H^{+} \right ]\left [ {CH_3COO}^- \right ]}{[CH_3COOH]}$

$1.8\times 10^{-5}=\frac{x^2}{1.8-x}$

$1.8\left(1.8-x\right)=100000x^2$

Solving for x, we get:

x = 0.00568 M

Percentage ionization = $\frac{0.00568}{1.8}\times 100=0.32 \%$

Option B is correct.

8 0

3 years ago

What is the effect of adding heat to a gas at constant pressure?

Anna007 [38]

The pressure will continue to build up eventually causing a release of pressure or an explosion.

8 0

3 years ago

How many stereoisomers are possible for 1 2-dichlorocyclopentane?

slega [8]

There are only three stereoisomers of 1,2-dimethylcyclopentane. As there are only two chiral carbons, so the maximum number of stereoisomers is 4, but two are the same meso-compound which means that there are only 3.

5 0

2 years ago