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2 years ago

calculate the ph of a 0.020 m carbonic acid solution, h2co3(aq), that has the stepwise dissociation constants ka1

Chemistry

1 answer:

fgiga [73]2 years ago

5 0

The calculated pH is 3.79. therefore, the solution is acidic.

No, carbonic acid is not a strong acid. H2CO3 is a weak acid that dissociates into a proton (H+ cation) and a bicarbonate ion (HCO3- anion). This compound only partly dissociates in aqueous solutions.

H2 CO3 = H (+) + HCO3(-) Ka1 = 4.3 * 10^ -7

0.06 - x x x

Ka1 = x^2 / (0.06 - x) = 4.3 * 10^ - 7

A low Ka => x << 0.06 => 0.06 -x ≈ 0.06

=> Ka1 ≈ x^2 / 0.06 => x^2 ≈ 0.06 * Ka1 = 0.06 * 4.3 * 10^-7

=> x ≈ √ [ 2.58 * 10 ^ -8] = 1.606 * 10^ - 4 = 0.0001606

Second dissociation

HCO3(-) = H (+) + CO3(2-) Ka2 = 5.6 * 10^ - 11

0.0001606 - y y y

Ka2 ≈ y^2 / 0.0001606 => y = √ [0.0001606 * 5.6* 10^ -11]

y = 9.48 * 10^ -8

An acidic solution has a high concentration of hydrogen ions (H +start superscript, plus, end superscript), greater than that of pure water.

[H+] = x + y = 1.607 * 10^ -4

pH = - log [H+] = 3.79

Learn more about concentration here-

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Rust is formed by the interaction of iron and oxygen. When rust formed on an iron nail with a mass of 100 g, the mass of the rus

DanielleElmas [232]

Answer: The correct option is A.

Explanation: Moles of Iron nail can be calculated by using the formula:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ ...(1)

Given mass of iron nail = 100 g

Molar mass of iron = 56 g/mol

$\text{Number of moles}=\frac{100g}{56g/mol}$

Number of moles of iron nail = 1.79 moles

The chemical equation for the formation of rust if given by:

$4Fe(s)+3O_2(g)\rightarrow 2Fe_2O_3(s)$

By Stoichiometry of the reaction,

4 moles of iron reacts with 3 moles of oxygen gas to produce 2 moles of rust.

So, 1.79 moles of iron will react with = $\frac{3}{4}\times 1.79$ = 1.3425 moles of oxygen gas.

For oxygen gas,

Molar mass = 32 g/mol

Mass of oxygen can be calculated by using equation 1, we get

$1.3425mol=\frac{\text{Given mass}}{32g/mol}$

Mass of oxygen gas = 43 grams

Hence, the correct option is a.

6 0

3 years ago

Na2CO3 + 2HCl ---------> 2NaCl + CO2 + H2O How many moles of NaCl are produced from the reaction of 1.67 x 1022 molecules of

dexar [7]

Answer:

0.0554 moles of NaCl are produced from the reaction of 1.67*10²² molecules of Na₂CO₃ with excess HCl.

Explanation:

The balanced reaction is:

Na₂CO₃ + 2 HCl → 2 NaCl + CO₂ + H₂O

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of each compound participate in the reaction:

Na₂CO₃: 1 mole
HCl: 2 moles
NaCl: 2 moles
CO₂: 1 mole
H₂O: 1 mole

On the other hand, Avogadro's Number is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023*10²³ particles per mole. Avogadro's number applies to any substance.

In this case, you can apply the following rule of three: if 6.023*10²³ molecules of Na₂CO₃ are contained in 1 mole, 1.67*10²² molecules will be contained in how many moles?

$amount of moles=\frac{1.67*10^{22}molecules*1mole }{6.023*10^{23}molecules}$

amount of moles= 0.0277 moles

In this case, you can apply the following rule of three: if by stoichiometry 1 mole of Na₂CO₃ produces 2 moles of NaCl, 0.0277 moles of Na₂CO₃ will produce how many moles of NaCl?

$amount of moles of NaCl=\frac{0.0277 moles of Na_{2} CO_{3}*2 moles of NaCl }{1 mole of Na_{2} CO_{3}}$

amount of moles of NaCl= 0.0554 moles

<u><em>0.0554 moles of NaCl are produced from the reaction of 1.67*10²² molecules of Na₂CO₃ with excess HCl.</em></u>

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Answer:

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