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3 years ago

Calculate each of the following quantities. (a) mass in kilograms of 3.7 x 1020 molecules of NO2

Chemistry

1 answer:

HACTEHA [7]3 years ago

7 0

Answer:

The answer to your question is: 0.028 kg of NO2

Explanation:

Data

3.7 x 10²⁰ molecules of NO2 in kg

MW of NO2 = 14 + (16 x 2) = 14 + 32 = 46 kg

1 mol of NO2 --------------------- 6.023 x 10 ²³ molecules

x --------------------- 3.7 x 10²⁰ molecules

x = 3.7 x 10²⁰ x 1 / 6.023 x 10 ²³

x = 0.00061 mol

1 mol of NO2 --------------------- 46 kg of NO2

0.00061 mol ------------------ x

x = 0.00061 x 46/1

x = 0.028 kg of NO2

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2 years ago

Calculate the concentration of formate in a 100mm solution of formic acid at ph 4.15. The pka for formic acid is 3.75

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The molarity of formic acid is 100 mM or $100\times 10^{-3}M$ . The dissociation reaction of formic acid is as follows:

$HCOOH\leftrightharpoons HCOO^{-}+H^{+}$

The expression for dissociation constant of the reaction will be:

$K_{a}=\frac{[HCOO^{-}][H^{+}]}{[HCOOH]}$

Rearranging,

$[HCOO^{-}]=\frac{K_{a}[HCOOH]}{[H^{+}]}$

Here, pH of solution is 4.15 thus, concentration of hydrogen ion will be:

$[H^{+}]=10^{-pH}=10^{-4.15}=7.08\times 10^{-5}M$

Similarly, $pK_{a}=3.75$ thus,

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Putting the values,

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2 years ago

The combustion of 40.10 g of a compound which contains only C, H, Cl and O yields 58.57 g of CO2 and 14.98 g of H2O. Another sam

elena-14-01-66 [18.8K]

Answer:

The empirical formula is C4H5ClO2

Explanation:

Step 1: Data given

Mass of the sample = 40.10 grams

Mass of CO2 produced = 58.57 grams

Mass of H2O produced = 14.98 grams

Molar mass CO2 = 44.01 g/mol

Molar mass H2O = 18.02 g/mol

Atomic mass C= 12.01 g/mol

Atomic mass O = 16.0 g/mol

Atomic mass H = 1.01 g/mol

In experiment 2, mass = 75.00 grams and 22.06 grams is Cl

Step 2: Calculate moles CO2

Moles CO2 = mass CO2 / molar mass CO2

Moles CO2 = 58.57 grams / 44.01 g/mol

Moles CO2 = 1.33 moles

Step 3: Calculate moles C

For 1 mol CO2 we have 1 mol CO2

For 1.33 moles CO2 we have 1.33 moles C

Step 4: Calculate mass C

Mass C = 1.33 grams * 12.01 g/mol

Mass C = 15.97 grams

Step 5: Calculate moles H2O

Moles H2O= 14.98 grams /18.02 g/mol

Moles H2O = 0.831 moles

Step 6: Calculate moles H

For 1mol H2O we have 2 moles H

For 0.831 moles H2O we have 2*0.831 = 1.662 moles H

Step7: Calculate mass H

Mass H = 1.662 moles * 1.01 g/mol

Mass H = 1.68 grams

Step 8: Calculate mass %

%C = (15.97 grams / 40.10) * 100 %

%C = 39.8 %

%H = (1.68 / 40.10 ) *100%

%H = 4.2 %

%Cl = (22.06 / 75.00 ) * 100%

%Cl = 29.4 %

%O = 100 % - 39.8% - 4.2 % - 29.4 %

%O = 26.6 %

Step 9: Calculate moles in compound

We assume the compound has a mass of 100 grams

Mass C = 39.8 grams

MAss H = 4.2 grams

MAss Cl = 29.4 grams

Mass O = 26.6 grams

Moles C = 39.8 grams / 12.01 g/mol

Moles C = 3.314 moles

Moles H = 4.2 moles / 1.01 g/mol

Moles H = 4.158 moles

Moles Cl =29.4 grams / 35.45 g/mol

Moles Cl = 0.829 moles

Moles O = 26.6 grams / 16.0 g/mol

Moles O = 1.663 moles

Step 10: calculate the mol ratio

We divide by the smallest amount of moles

C: 3.314 moles / 0.829 moles = 4

H: 4.158 moles / 0.829 moles = 5

Cl: 0.829 moles /0.829 moles = 1

O: 1.663 moles / 0.829 moles = 2

This means For each Cl atom we have 4 C atoms, 5 H atoms and 2 O atoms

The empirical formula is C4H5ClO2

5 0

3 years ago