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3 years ago

What mass (in g) of NH3 must be dissolved in 475 g of methanol to make a 0.250 m solution?

Chemistry

1 answer:

Tema [17]3 years ago

5 0

Answer:

We need 2.02 grams of NH3

Explanation:

Step 1: Data given

Mass of methanol = 475 grams

Molality of the solution = 0.250 M

Molar mass of NH3 =17.03 g/mol

Molar mass of = methanol = 32.04g/mol

Step 2: Calculate moles NH3

Molality = 0.250 m = mol NH3 / 0.475 kg

moles NH3 = 0.250 molal * 0.475 kg

Moles NH3 = 0.11875 moles

Step 3: Calculate the mass of NH3

Mass NH3 = moles NH3 * molar mass NH3

Mass NH3 = 0.11875 mol * 17.03 g/mol

Mass NH3 = 2.02 grams

We need 2.02 grams of NH3

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What is the freezing point of a solution of 498mL of water (solute) dissolved in 2.50 L of ethanol (solvent), C2H5OH? The densit

jok3333 [9.3K]

Answer:

Freezing T° of solution is -142.4°C

Explanation:

This excersise is about colligative properties, in this case freezing point depression,

ΔT = Kf . m . i

Where ΔT = Freezing T° of solvent - Freezing T° of solution

Kf = Cryoscopic constant

m = mol/kg (molality)

i = Number of ions dissolved.

Water is not ionic, so i = 1

Let's find out m.

We determine mass of water, by density

498ml . 1 g/mL = 498 g

We convert the mass of water to moles → 498 g . 1mol/18g = 27.6 moles

We determine mass of solvent by density

2500 mL . 0.789 g/mL = 1972.5 g

Notice, we had to convert L to mL to cancel units.

1 cm³ = 1 mL

We convert the mass from g to kg → 1972.5 g . 1kg /1000g = 1.97kg

We determine m = mol/kg → 27.6mol / 1.97kg = 13.9 m

Kf for ethanol is: 1.99 °C/m

Freezing T° for ethanol is: -114.6°C

We replace at formula: - 114.6°C - Freezing T° solution = 1.99 °C/m . 13.9 m . 1

- 114.6°C - Freezing T° solution = 27.8 °C

- Freezing T° solution = 27.8°C + 114.6°C

Freezing T° Solution = - 142.4 °C

7 0

2 years ago

A __________ has distinct properties and composition that never vary.

erik [133]

<h2>Answer </h2>

Matter

Explanation

A matter has distinct properties and composition that never vary. The matter is anything which possesses mass and occupies space. The matter has different characteristics and a distribution that does not change from unit to unit. Materials which cannot be disintegrated into simpler materials. Each is made of only one kind of atom in subatomic level. For example, a chair, table, and similar everything that has mass and occupies space is matter.

3 0

2 years ago

Read 2 more answers

_H3PO4 + _HCl --->_PCl5 + _H2O

Slav-nsk [51]

Dennis g studio and I don't have any money

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2 years ago

What is the volume of 40.0 grams of argon gas at STP ?

MrRa [10]

Answer:

24.9 L Ar

General Formulas and Concepts:

Atomic Structure

Reading a Periodic Table
Moles
STP (Standard Conditions for Temperature and Pressure) = 22.4 L per mole at 1 atm, 273 K

Aqueous Solutions

States of Matter

Stoichiometry

Using Dimensional Analysis

Explanation:

Step 1: Define

[Given] 40.0 g Ar

[Solve] L Ar

Step 2: Identify Conversions

[PT] Molar Mass of Ar - 39.95 g/mol

[STP] 22.4 L = 1 mol

Step 3: Convert

[DA] Set up: $\displaystyle 40.0 \ g \ Ar(\frac{1 \ mol \ Ar}{39.95 \ g \ Ar})(\frac{22.4 \ L \ Ar}{1 \ mol \ Ar})$
[DA] Divide/Multiply [Cancel out units]: $\displaystyle 24.9235 \ L \ Ar$

Step 4: Check

Follow sig fig rules and round. We are given 3 sig figs.

24.9235 L Ar ≈ 24.9 L Ar

5 0

2 years ago

What do Potassium and Krypton have in common and what are their differences based on their location on the periodic table?

andreev551 [17]

Common based on their location in Periodic Table;

Potassium has an atomic number 19. Its electronic configuration is as follow;

1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹

And Krypton has an atomic number of 36. Its electronic configuration is as follow;

1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶

It is concluded that both Potassium and Krypton has their valence electrons in 4rth shell or they have same Principle Quantum Number.

Difference based on their location in Periodic Table;

As observed in electronic configuration Potassium has one valence electron in its valence shell (i.e. 4s¹) while, Krypton has eight valence electrons in its valence shell (i.e. 4s², 4p⁶). Therefore, they are different in the number of valence electrons.

6 0

3 years ago