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2 years ago

Electrons orbit the nucleus in specified energy

Chemistry

1 answer:

pashok25 [27]2 years ago

5 0

Answer:

because the electron is a negatively charge and have high energy

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how many moles of a nonvolatile, nonelectrolyte solute are required to lower the freezing point of 1000 grams of water by 5.58

Ivan

Answer:

Explanation:

Using freezing point depression formula,

ΔTemp.f = Kf * b * i

Where,

ΔTemp.f = temp.f(pure solvent) - temp.f(solution)

b = molality

i = van't Hoff factor

Kf = cryoscopic constant

= 1.86°C/m for water

= (0 - (-5.58))/1.86

= 3.00 mol/kg

Assume 1 kg of water(solvent)

= (3.00 x 1)

= 3.00 mol.

5 0

3 years ago

A chemistry student needs to standardize a fresh solution of sodium hydroxide. He carefully weighs out 28.mg of oxalic acid H2C2

Nezavi [6.7K]

Answer:

The molarity of the student's sodium hydroxide solution is 0.0219 M

Explanation:

1) Chemical reaction.

a) Kind of reaction: neutralization

b) General form: acid + base → salt + water

c) Word equation:

sodium hydroxide + oxalic acid → sodium oxalate + water

d) Chemical equation:

NaOH + H₂C₂O₄ → Na₂C₂O₄ + H₂O

b) Balanced chemical equation:

2NaOH + H₂C₂O₄ → Na₂C₂O₄ + 2H₂O

2) Mole ratio

2mol Na OH : 1 mol H₂C₂O₄ :1 mol Na₂C₂O₄ : 2 mol H₂O

3) Starting amount of oxalic acid

mass = 28 mg = 0.028 g
molar mass = 90.03 g/mol
Convert mass in grams to number of moles, n:

n = mass in grams / molar mass = 0.028 g / 90.03 g/mol = 0.000311 mol

4) Titration

Volume of base: 28.4 mL = 0.0248 liter
Concentration of base: x (unknwon)

Number of moles of acid: 2.52 mol (calculated above)

Proportion using the theoretical mole ratio (2mol Na OH : 1 mol H₂C₂O₄)

$\frac{2}{1} =\frac{x}{2.52}\\ \\ \\x=0.000311(2)=0.000622$

That means that there are 0.000622 moles of NaOH (solute)

5) Molarity of NaOH solution

M = n / V (liter) = 0.000622 mol / 0.0284 liter = 0.0219 M

That is the correct number using three signficant figures, such as the starting data are reported.

5 0

3 years ago

Read 2 more answers

Researchers are investigating processes that happen during digestion. Which answer choice describes only a physical change durin

ElenaW [278]

The correct answer is B. Chewing in the mouth breaks food into small pieces.

Explanation:

In physical changes, substances do not change their chemical composition or properties but only physical features such as this. This occurs during the chewing because the action of chewing only makes food to be broken down in smaller pieces but does not change its identity, composition, or properties. This does not occur once the food is in contact with saliva, the acid in the stomach, etc. because in these cases, the food reacts with other substances and a chemical reaction occurs, which changes food's identity and composition.

8 0

2 years ago

In a calorimetry experiment, a salt is dissolved in water within an insulating container. The temperature of the solution (surro

Stels [109]

Answer:

Explanation:

heat released by the solution

= 120 x 3.18 x ( 25 - 14 )

= 4197.6 J

= 4.1976 kJ

This is the heat gain by the salt

so enthalpy change = + 4.1976 kJ

because there is increase in enthalpy

It is endothermic process .

7 0

2 years ago

What is the volume of a rectangular prism that has a length of 7 cm, width of 8 cm, and height of 14 cm? A. 392 cm3 B. 29 cm3 C.

Shtirlitz [24]

Volume = l x w x h
volume = 7 x 8 x 14
volume = 784...... C

4 0

2 years ago