Chemistry, 10.11.2019 19:31 bl88676

When ammonia, nh3, dissolves in water, hydrogen ions are transferred from the water to ammonia to form ammonium ions and hydroxide ions. this reaction can be seen below:

h2o (l) + nh3 (aq) yields oh- (aq) + nh4+ (aq)

which of the following to explain why ammonia is a base?
a. arrhenius definition
b. bronsted- lowry definition
c. lewis definition
d. ionization definition

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I believe the answer is C. It is the Lewis definition that helps explain why ammonia is a base. According to Lewis' definition, bases donate electrons while the acids accept these electron. In the reaction, ammonia releases electron while the water accepts it.

Answer from: pandadude123

Bronsted- Lowry definition helps to explain why ammonia is a base.

Explanation:

The Brönsted - Lowry theory states that acids are substances capable of yielding protons (hydrogen H⁺ ions) and substance bases capable of accepting them.

Then, the acid-base reaction is one in which a transfer of H⁺ protons occurs from an acid to a base.

A base acid conjugate pair is then produced, where the base conjugate acid is the one formed when the base receives an H⁺; and the conjugate base of the acid, is the base formed when the acid yields an H⁺.

You know this reaction:

H₂O (l) + NH₃ (aq) → OH⁻ (aq) + NH₄⁺ (aq)

In this case you can see that the water acts as an acid, because it gives a proton to the ammonia. Then the ammonia will act as the basis for accepting the proton. The conjugate base of water is the hydroxide ion (OH⁻) and the conjugated acid of ammonia is the ammonium ion (NH₄⁺).

Then, Bronsted- Lowry definition helps to explain why ammonia is a base.

Answer from: Quest

i have no clue hope you find the answer

Answer from: Quest

the missing options are :

(1) lower boiling point and a lower freezing point(2) lower boiling point and a higher freezing point(3) higher boiling point and a lower freezing point(4) higher boiling point and a higher freezing point

answer : the correct answer is option (3) higher boiling point and a lower freezing point

explanation :

when a non volatile solute is added to a solvent like water, it results in elevation of boiling point.

let us find the increase in boiling point of water when cacl₂ is added to water to make a solution of 1 m

step 1 : find molality of the solution

let us assume we have 1 l of solution.

$m = \frac{moles (solute)}{l ( solution)}$

$1 m = \frac{moles (cacl_{2})}{1 l }= 1 mol cacl_{2}$

let us convert this to grams of cacl₂.

molar mass of cacl2 is 111 g/mol

grams of cacl₂ = $1 mol \times \frac{111g}{mol} = 111 g cacl_{2}$

mass of solute = 111 g

assuming density of solution same as water which is 1g/ml we have ,

mass of solution = density * volume

mass of solution = $\frac{1g}{ml} \times 1000 ml = 1000 g$

mass of solution = mass of solvent + mass of solute

mass of solute = 1000g - 111g

mass of solute 889 g = 0.889 kg

the molality of the solution can be calculated as

$molality = \frac{mol (solute)}{kg ( solvent)}$

$molality = \frac{1mol}{0.889kg}$

molality = 1.12 m

step 2 : find boiling point elevation.

the elevation in boiling point is calculated as

$\bigtriangleup t_{b} = i \times k_{b} \times m$

here δtb = boiling point elevation

i = vant hoff factor which is the number of ions formed by the solute .

cacl₂ dissociates as $cacl_{2} \rightarrow ca^{2+} + 2 cl^{-}$

it forms 3 ions . therefore,

i = 3

m = molality which is 1.12 m

kb is constant for a given solvent. for water it is 0.512

$\bigtriangleup t_{b} = 3 \times 0.512 \times 1.12$

$\bigtriangleup t_{b} = 1.7$

the boiling point of water increases by 1.7 °c

step 3: find freezing point depression.

when a non volatile solute is added to water, it results in decrease in freezing point.

the formula to find freezing point depression is

$\bigtriangleup t_{f} = i \times k_{f} \times m$

kf is constant for water and its value is 1.86

$\bigtriangleup t_{f} = 3 \times 1.86 \times 1.12$

$\bigtriangleup t_{f} = 6.2$

the freezing point of water decreases by 6.2 °c

therefore we can say that, the solution will have a higher boiling point and a lower freezing point

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