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3 years ago

How many grams of solid Na2CO3 are required to neutralize exactly 2 liters of an HCI solution of pH 2.0?

Chemistry

1 answer:

Snezhnost [94]3 years ago

3 0

Answer:

The answer is 1.06g.

Explanation:

Analysis of question:

1. Identify the information in the question given.

volume of HCl is 2 dm3
pH of HCl is 2.0

2. What the question want?

mass of Na2CO3 is ?(unknown)
3. Do calculation.
1st-Write a balanced chemical equation:

Na2CO3 + 2HCl (arrow) 2NaCl + H20 + CO2

2nd-Determine the molarity of HCl with the value of 2.0.

pH= -log[H+]

2.0= -log[H+]

log[H+]= -2.0

[H+]= 10 to the power of negative 2(10-2)

=0.01 mol dm-3

molarity of HCl is 0.01 mol dm-3

3rd-Find the number of moles of HCl

n=MV

=0.01 mol dm-3 × 2 dm3

=0.02 mol of HCl

4th-Find the second mol of it.

Based on the chemical equation,

2.0 mol of HCl reacts with 1.0 mol of Na2CO3

0.02 mol of HCl reacts with 0.01 mol of Na2CO3

Na2CO3>a=1 mol

2HCl>b=2 mol

5th-Find the mass of it.

mass= number of mole × molar mass

g=0.01 × [2(23)+ 12+ 3(16)]

g=0.01 × 106

# =1.06 g.

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Answer:

For A: The number of arsenic atoms are $3.4\times 10^{21}$

For B: The percent composition of mercury, thallium and chromium in their complexes are 61.76 %, 62.2 % and 29.51 % respectively.

Explanation:

For A:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of dimercaprol = 696 mg = 0.696 g (Conversion factor: 1 g = 1000 mg)

Molar mass of dimercaprol = 124.21 g/mol

Putting values in above equation, we get:

$\text{Moles of dimercaprol}=\frac{0.696g}{124.21g/mol}=0.0056mol$

According to mole concept:

1 mole of a compound contains $6.022\times 10^{23}$ number of molecules.

So, 0.0056 moles of dimercaprol will contain $0.0056\times 6.022\times 10^{23}=3.4\times 10^{21}$ number of molecules.

As, 1 molecule of dimercaprol binds with 1 atom of Arsenic

So, $3.4\times 10^{21}$ number of dimercaprol molecules will bind with = $1\times 3.4\times 10^{21}=3.4\times 10^{21}$ number of arsenic atoms

Hence, the number of arsenic atoms are $3.4\times 10^{21}$

For B:

We know that:

Molar mass of dimercaprol = 124.21 g/mol

Molar mass of mercury = 200.59 g/mol

Molar mass of thallium = 204.38 g/mol

Molar mass of chromium = 51.99 g/mol

Also, 1 molecule of dimercaprol binds with 1 metal atom.

To calculate the percentage composition of metal in a complex, we use the equation:

$\%\text{ composition of metal}=\frac{\text{Mass of metal}}{\text{Mass of complex}}\times 100$ ......(1)

For mercury:

Mass of Hg-complex = (200.59 + 124.21) = 324.8 g

Mass of mercury = 200.59 g

Putting values in equation 1, we get:

$\%\text{ composition of mercury}=\frac{200.59g}{324.8g}\times 100=61.76\%$

For thallium:

Mass of Tl-complex = (204.38 + 124.21) = 328.59 g

Mass of thallium = 204.38 g

Putting values in equation 1, we get:

$\%\text{ composition of thallium}=\frac{204.38g}{328.59g}\times 100=62.2\%$

For chromium:

Mass of Cr-complex = (51.99 + 124.21) = 176.2 g

Mass of chromium = 51.99 g

Putting values in equation 1, we get:

$\%\text{ composition of chromium}=\frac{51.99g}{176.2g}\times 100=29.51\%$

Hence, the percent composition of mercury, thallium and chromium in their complexes are 61.76 %, 62.2 % and 29.51 % respectively.

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ioda

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Explanation:

This question is asking to write and balance an equation between between aqueous sodium carbonate (Na2CO3) and aqueous nitric acid (HNO3). The equation is as follows:

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