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inessss [21]
3 years ago
14

how many grams of antifreeze would be required per 500 g of water to prevent the water from feezing at a temperature of -39° C​

Chemistry
1 answer:
andrezito [222]3 years ago
4 0

Answer:

333.7g of antifreeze

Explanation:

Freezing point depression in a solvent (In this case, water) occurs by the addition of a solute. The law is:

ΔT = Kf × m × i

Where:

ΔT is change in temperature (0°C - -20°C = 20°C)

Kf is freezing point depression constant (1.86°C / m)

m is molality of solution (moles solute / 0.5 kg solvent -500g water-)

i is Van't Hoff factor (1, assuming antifreeze is ethylene glycol -C₂H₄(OH)₂)

Replacing:

20°C = 1.86°C / m  × moles solute / 0.5 kg solvent × 1

5.376 = moles solute

As molar mass of ethylene glycol is 62.07g/mol:

5.376 moles × (62.07g / 1mol) = <em>333.7g of antifreeze</em>.

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Problem PageQuestion The airbags that protect people in car crashes are inflated by the extremely rapid decomposition of sodium
Shalnov [3]

Answer:

1. 2NaN₃(s) → 2Na(s) + 3N₂(g)

2. 14.5 g NaN₃

Explanation:

The answer is incomplete, as it is missing the required values to solve the problem. An internet search shows me these values for this question. Keep in mind that if your values are different your result will be different as well, but the solving methodology won't change.

" The airbags that protect people in car crashes are inflated by the extremely rapid decomposition of sodium azide, which produces large volumes of nitrogen gas. 1. Write a balanced chemical equation, including physical state symbols, for the decomposition of solid sodium azide (NaN₃) into solid sodium and gaseous dinitrogen. 2. Suppose 71.0 L of dinitrogen gas are produced by this reaction, at a temperature of 16.0 °C and pressure of exactly 1 atm. Calculate the mass of sodium azide that must have reacted. Round your answer to 3 significant digits. "

1. The <u>reaction that takes place is</u>:

  • 2NaN₃(s) → 2Na(s) + 3N₂(g)

2. We use PV=nRT to <u>calculate the moles of N₂ that were produced</u>.

P = 1 atm

V = 71.0 L

n = ?

T = 16.0 °C ⇒ 16.0 + 273.16 = 289.16 K

  • 1 atm * 71.0 L = n * 0.082 atm·L·mol⁻¹·K⁻¹ * 289.16 K
  • n = 0.334 mol

Now we <u>convert N₂ moles to NaN₃ moles</u>:

  • 0.334 mol N₂ * \frac{2molNaN_{3}}{3molN_2} = 0.223 mol NaN₃

Finally we <u>convert NaN₃ moles to grams</u>, using its molar mass:

  • 0.223 mol NaN₃ * 65 g/mol = 14.5 g NaN₃

6 0
3 years ago
In standardizing a naoh solution a student found that 25.55cm of base neutralize exactly 21.35cm of 0.12M HCl find the molarity
nalin [4]

Answer:

O.1M

Explanation:

First let's generate a balanced equation for the reaction

NaOH + HCl —>NaCl + H2O

From the equation,

The ratio of the acid to base is 1:1.

From the question, we obtained the following:

Ma = Molarity of acid = 0.12M

Va = volume of acid = 21.35cm3

Vb = volume of base = 25.55cm3

Mb = Molarity of base =?

We obtained nA(mole of acid) and nB(mole of base) to be 1

The molarity of the base can be calculated for using:

MaVa/ MbVb = nA / nB

0.12x21.35 / Mb x 25.55 = 1

Cross multiply to express in linear form

Mb x 25.55 = 0.12x21.35

Divide both side by 25.55

Mb = (0.12x21.35) / 25.55

Mb = 0.1M

The molarity of the base is 0.1M

6 0
2 years ago
A weak base. B. has a K. of 4.46 x 10-10 A solution with an unknown initial concentration is tested, and found to have a pH of 8
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Answer:

0.013MB

Explanation:

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wlad13 [49]

The answers are B, C, and D.

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3 years ago
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