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3 years ago

HELP ASAP MY LESSON IS BEING TIMED!!!

Chemistry

2 answers:

77julia77 [94]3 years ago

7 0

Answer:

1. Newton's third law of motion

2. Unbalanced

3. Action

Ugo [173]3 years ago

7 0

It’s action for number 3

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Give five properties of water.

Gelneren [198K]

Polarity, cohesion, adhesion, surface tension, high specific heat, and evaporating cooling

3 0

3 years ago

Read 2 more answers

(3) A 10.00-mL sample of 0.1000 M KH2PO4 was titrated with 0.1000 M HCl Ka for phosphoric acid (H3PO4): Ka1= 7.50x10-3; Ka2=6.20

shtirl [24]

Answer:

The pH of this solution is 1,350

Explanation:

The phosphoric acid (H₃PO₄) has three acid dissociation constants:

HPO₄²⁻ ⇄ PO4³⁻ + H⁺ Kₐ₃ = 4,20x10⁻¹⁰ (1)

H₂PO₄⁻ ⇄ HPO4²⁻ + H⁺ Kₐ₂ = 6,20x10⁻⁸ (2)

H₃PO₄ ⇄ H₂PO4⁻ + H⁺ Kₐ₁ = 7,50x10⁻³ (3)

The problem says that you have 10,00 mL of KH₂PO₄ (It means H₂PO₄⁻) 0,1000 M and you add 10,00 mL of HCl (Source of H⁺) 0,1000 M. So you can see that we have the reactives of the equation (3).

We need to know what is the concentration of H⁺ for calculate the pH.

The moles of H₂PO₄⁻ are:

10,00 mL × ( 1x10⁻⁴ mol / mL) = 1x10⁻³ mol

The moles of H⁺ are, in the same way:

10,00 mL × ( 1x10⁻⁴ mol / mL) = 1x10⁻³ mol

So:

H₃PO₄ ⇄ H₂PO4⁻ + H⁺ Kₐ₁ = 7,50x10⁻³ (3)

X mol ⇄ (1x10⁻³-X) mol + (1x10⁻³-X) mol (4)

The chemical equilibrium equation is:

Kₐ₁ = ([H₂PO4⁻] × [H⁺] / [H₃PO₄]

So:

7,50x10⁻³ = (1x10⁻³-X)² / X

Solving the equation you will obtain:

X² - 9,5x10⁻³ X + 1x10⁻⁶ = 0

Solving the quadratic formula you obtain two roots:

X = 9,393x10⁻³ ⇒ This one has no chemical logic because solving (4) you will obtain negative H₂PO4⁻ and H⁺ moles

X = 1,065x10⁻⁴

So the moles of H⁺ are : 1x10⁻³- 1,065x10⁻⁴ : 8,935x10⁻⁴ mol

The reaction volume are 20,00 mL (10,00 from both KH₂PO₄ and HCL)

Thus, the molarity of H⁺ ([H⁺]) is: 8,935x10⁻⁴ mol / 0,02000 L = 4,468x10⁻² M

pH is -log [H⁺]. So the obtained pH is 1,350

I hope it helps!

5 0

3 years ago

Calculate the mass of Na2O that can be produced by the chemical reaction of 4.0 grams of sodium with excess oxygen in the reacti

e-lub [12.9K]

Answer:

The mass of Na₂O that can be produced by the chemical reaction of 4.0 grams of sodium with excess oxygen in the reaction is 5.39 grams.

Explanation:

You know the balanced reaction:

4 NA + O₂ ⟶ 2 Na₂O

By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction) react and are produced:

Na: 4 moles
O₂: 1 mole
Na₂O: 2 moles

Being:

Na: 23 g/ole
O: 16 g/mole

the molar mass of the compounds participating in the reaction is:

Na: 23 g/mole
O₂: 2*16 g/mole= 32 g/mole
Na₂O: 2*23 g/mole +16 g/mole= 62 g/mole

Then by stoichiometry of the reaction they react and are produced:

Na: 4 moles* 23 g/mole= 92 g
O₂: 1 mole*32 g/mole= 32 g
Na₂O: 2 moles* 62 g/mole= 124 g

Then you can apply the following rule of three: if 92 grams of Na produce 124 grams of Na₂O, 4 grams of Na, how much mass of Na₂O does it produce?

$massofNa_{2}O =\frac{4 grams of Na*124 gramsofNa_{2}O }{92 grams of Na}$

mass of Na₂O=5.39 g

<em><u>The mass of Na₂O that can be produced by the chemical reaction of 4.0 grams of sodium with excess oxygen in the reaction is 5.39 grams.</u></em>

8 0

3 years ago

What changes happens when you run ?

oksano4ka [1.4K]

Answer:

It increases endurance, builds muscle to maintain an optimal body fat composition, promotes cardiovascular health, strengthens the heart, and even improves your overall mood. Combined with weight training, running can help you maintain the perfect balance of mental stimulation and physical fitness.

Explanation:

4 0

3 years ago

The government, through the FCC (Federal Communications Commission), has set rules and guidelines for the use of radio equipment

Doss [256]

Answer:

Wavelength = 0.06024 m

Explanation:

Equation of energy of wavelength from Einstein's relativity equation is;

E = hc/λ

Where;

h is Planck's constant = 6.626 × 10⁻³⁴ J. s

c is speed of light = 3 × 10⁸

We are given E = 3.3 × 10^(-24) J

Making wavelength λ the subject, we have;

λ = hc/E

Thus;

(6.626 × 10⁻³⁴ × 3 × 10⁸)/(3.3 × 10^(-24)) = 6.024 × 10^(-2) = 0.06024 m

Wavelength = 0.06024 m

5 0

3 years ago