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Lelu [443]
4 years ago
13

Explain to to me about lanthanum

Chemistry
1 answer:
BabaBlast [244]4 years ago
7 0
Atomic number is 57, and the atomic mass is 138.90547 u + 0.00007 u
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Solubility. In each of the following pairs of amino acids, identify which amino acid would be most soluble in water: (a) Ala, Le
Svetllana [295]

Answer:

(a) Ala; (b) Tyr; (c) Ser; (d) His

Explanation:

The general formula for an amino acid is NH₂-CH(R)-COOH

The differences among the different amino acids is caused by the side groups R.

(a) Ala, Leu

Ala: R =                 CH₃-

Leu: R = (CH₃)₂CHCH₂-

Leucine has a larger hydrophobic side group. It should be the less soluble of the pair,

Alanine is the more soluble amino acid.

(b) Tyr, Phe

Tyr: R = HOC₆H₄CH₂-

Phe: R =      C₆H₅CH₂-

Tyrosine has a polar OH group. It can form hydrogen bonds with water.

Tyrosine is the more soluble amino acid.

(c) Ser, Ala

Ser: R = HOCH₂-

Ala: R =       CH₃-

Serine has a polar OH group. It can form hydrogen bonds with water.

Serine is the more soluble amino acid.

(d) Trp, His

Trp: R =       Indole-CH₂-

His: R = Imidazole-CH₂-

Tryptophan has a large aromatic hydrophobic side chain.

Histidine is a basic amino acid. At pH 7 it exists mainly as the anion NH₂CHRCOO⁻, which is hydrophilic.

Histidine is the more soluble amino acid.

4 0
3 years ago
Which two physical properties allow a mixture to be separated by chromatography
Slav-nsk [51]

Answer:


                 Option-1 (Solubility and Molecular polarity) is the correct answer.


Explanation:


                        Thin Layer Chromatography is employed to separate a mixture of non volatile compounds. In this technique an adsorbent material like silica gel is coated on a plastic, glass or aluminium sheet. Then the mixture of compounds is applied at the bottom of sheet and the sheet is placed in the container containing a solvent system. It is observed that the solvent starts travelling upward through capillary action.


While the solvent is running the mixture of compounds starts separating from each other. This separation is due to following physical properties.


1) Solubility of Mixture in Solvent:

                                                          In a mixture those compounds which has more solubility in solvent will travel more and will give greater Rf value and the less soluble will left behind with smaller Rf value. Hence due to solubility a mixture of compounds can be separated.


2) Polarity of Molecules:

                                          As the stationary phase (adsorbent material) is polar in nature, so in mixture those compounds which are less polar will less interact with the stationary phase and will travel more with greater Rf value, while, more polar molecules will form stronger interactions with the stationary phase, hence will travel less and therefore, will show smaller Rf values.


6 0
3 years ago
What are the 3 common gases that give off reactions?
Serjik [45]

The 3 common gases that give off reactions are Hydrogen sulfide, Carbon monoxide, Nitrogen oxides.

<h3>What are off reactions</h3>

Off reactions are defined as chemical reactions that occurs when something burns or during combustion of materials which gives off energy.

Some gases that give off reaction are:

  1. Hydrogen sulfide
  2. Carbon monoxide
  3. Nitrogen oxides

Note that these gases are mostly poisonous.

Therefore, the 3 common gases that give off reactions are Hydrogen sulfide, Carbon monoxide, Nitrogen oxides.

Learn more about off reactions here:

brainly.com/question/16416932

#SPJ12

3 0
2 years ago
How many moles are in 3.45 g of Na2O?Round your answer to three significant
Neporo4naja [7]

Answer: There are 0.056 moles present in 3.45 g of Na_{2}O.

Explanation:

Given : Mass = 3.45 g

Moles is the mass of substance divided by its molar mass.

Hence, moles of Na_{2}O (molar mass = 61.98 g/mol) is as follows.

Moles = \frac{mass}{molar mass}\\= \frac{3.45 g}{61.98 g/mol}\\= 0.056 mol

Thus, we can conclude that there are 0.056 moles present in 3.45 g of Na_{2}O.

6 0
3 years ago
Assuming ideal solution behavior, what is the freezing point of a solution of 9.04 g of I2 in 75.5 g of benzene?
cluponka [151]

Answer:

3.1°C

Explanation:

Using freezing point depression expression:

ΔT = Kf×m×i

<em>Where ΔT is change in freezing point, Kf is freezing point depression constant (5.12°c×m⁻¹), m is molality of the solution and i is Van't Hoff factor constant (1 For I₂ because doesn't dissociate in benzene).</em>

Molality of 9.04g I₂ (Molar mass: 253.8g/mol) in 75.5g of benzene (0.0755kg) is:

9.04g ₓ (1mol / 253.8g) = 0.0356mol I₂ / 0.0755kg = 0.472m

Replacing in freezing point depression formula:

ΔT = 5.12°cm⁻¹×0.472m×1

ΔT = 2.4°C

As freezing point of benzene is 5.5°C, the new freezing point of the solution is:

5.5°C - 2.4°C =

<h3>3.1°C</h3>

<em />

3 0
3 years ago
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