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aev [14]
3 years ago
13

How many atoms are in a sample of 72.8 grams calcium ?

Chemistry
1 answer:
MArishka [77]3 years ago
6 0
First find the moles
moles of the calcium= 72.8 / 40
moles of calcium in 72.8g = 1.82mol

number of atoms= moles x Avogadro constant
atoms = 1.82 x 6.02x10+23
so the number of atoms is 1.096x10+24
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What is the pH of 0.166 M triethylammonium chloride, (C2H5)3NHCl. The Kb of triethylamine, (C2H5)3N, is 5.2 x 10-4.?
777dan777 [17]

Answer:

5.7

Explanation:

(C₂H₅)₃NHCl dissociates according to the following equation.

(C₂H₅)₃NHCl ⇒ (C₂H₅)₃NH⁺ + Cl⁻

The molar ratio of (C₂H₅)₃NHCl to (C₂H₅)₃NH⁺ is 1:1. Then, the concentration of (C₂H₅)₃NH⁺ is Ca = 0.166 M.

(C₂H₅)₃NH⁺ is the conjugate acid of (C₂H₅)₃N. Given the Kb of (C₂H₅)₃N, we can calculate Ka for (C₂H₅)₃NH⁺ using the following expression.

Ka × Kb = Kw

Ka = Kw / Kb

Ka = 1.0 × 10⁻¹⁴ / 5.2 × 10⁻⁴

Ka = 1.9 × 10⁻¹¹

(C₂H₅)₃NH⁺ dissociates according to the following equation.

(C₂H₅)₃NH⁺ ⇄ (C₂H₅)₃N + H⁺

We can calculate [H⁺] using the following expression.

[H⁺] = √(Ca × Ka) = √(0.166 × 1.9 × 10⁻¹¹) = 1.8 × 10⁻⁶

The pH is:

pH = -log [H⁺] = -log 1.8 × 10⁻⁶ = 5.7

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4 years ago
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How can we increase the rate of collisions between the reactants in this reaction? mg 2hcl → mgcl2 h2
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Increasing a reactant's surface area increases the frequency of collisions and thus the reaction rate. The surface area of several smaller particles is greater than that of a single large particle. The greater the available surface area for particles to collide, the faster the reaction will occur.

<h3>How does concentration affect the rate of collisions between reactants?</h3>

Thus, we can conclude that by increasing the concentration of Mg in the reaction mixture we increase the rate of collisions between the reactants in this reaction.

<h3>What does the half reaction of an oxidation-reduction reaction show?</h3>

Iron gains electrons in the half reaction of an oxidation-reduction reaction. What does iron's electron gain mean? It has been reduced. Predict the product that will precipitate out of the reaction using the solubility rules and the periodic table.

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4 0
2 years ago
A solution is 40.0% by volume benzene (C6H6) in carbon tetrachloride at 20C. The vapor pressure of pure benzene at this temperat
Alexandra [31]

Answer:

84.30 mm Hg

Explanation:

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Ptotal = XAPºA + XBPºB

where XA= mol fraction =na/(na +nb) and PºA vapor pressure pure of pure component A

m C6H6 = 40 cm³ x 0.87865 g/cm³ = 35.146 g

mol C6H6 = 35.146 g/ 78.11 g/mol = 0.45 mol

mass CCl4 = 60 cm³ x 1.5940 g/cm³ = 95.640 g

mol CCl4 = 95.640 g / 153.82 g/mol = 0.62 mol

mol tot = 1.07

XC6H6 = 0.45/ 1.07 = 0.42      XCCl4 = 0.62/1.07 =0.58

Ptot (mmHg) = 0.42 x 74.61 + .58 x 91.32 = 84.30 mmHg

6 0
3 years ago
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