Which of the following feedbacks can be either positive or negative?

What mass of potassium hypochlorite (FW-90.6 g/mol) must be added to 4.50 x 10 mL of water to give a solution with pH 10.20? [Ka

marta [7]

Answer : The mass of potassium hypochlorite is, 4.1 grams.

Explanation : Given,

pH = 10.20

Volume of water = $4.50\times 10^2ml=0.45L$

The decomposition of KClO will be :

$KClO\rightarrow K^++ClO^-$

Now the further reaction with water $(H_2O)$ to give,

$ClO^-+H_2O\rightarrow HClO+OH^-$

First we have to calculate the pOH.

$pH+pOH=14\\\\pOH=14-pH\\\\pOH=14-10.20=3.8$

Now we have to calculate the $OH^-$ concentration.

$pOH=-\log [OH^-]$

$3.8=-\log [OH^-]$

$[OH^-]=1.58\times 10^{-4}M$

Now we have to calculate the base dissociation constant.

Formula used : $K_b=\frac{K_w}{K_a}$

Now put all the given values in this formula, we get :

$K_b=\frac{1.0\times 10^{-14}}{4.0\times 10^{-8}}=2.5\times 10^{-7}$

Now we have to calculate the concentration of $ClO^-$ .

The equilibrium constant expression of the reaction is:

$K_b=\frac{[OH^-][HClO]}{[ClO^-]}$

As we know that, $[OH^-]=[HClO]=1.58\times 10^{-4}M$

$2.5\times 10^{-7}=\frac{(1.58\times 10^{-4})^2}{[ClO^-]}$

$[ClO^-]=0.0999M$

Now we have to calculate the moles of $ClO^-$ .

$\text{Moles of }ClO^-=\text{Molarity of }ClO^-\times \text{Volume of solution}$

$\text{Moles of }ClO^-=0.0999mole/L\times 0.45L=0.0449mole$

As we know that, the number of moles of $ClO^-$ are equal to the number of moles of KClO.

So, the number of moles of KClO = 0.0449 mole

Now we have to calculate the mass of KClO.

$\text{Mass of }KClO=\text{Moles of }KClO\times \text{Molar mass of }KClO$

$\text{Mass of }KClO=0.0449mole\times 90.6g/mole=4.07g\approx 4.1g$

Therefore, the mass of potassium hypochlorite is, 4.1 grams.

6 0

3 years ago

3g of magnesium reacted w 0.2 moles of ethanoic acid. Calculate the number of moles of magnesium used

marishachu [46]

Answer:

0.1 moles of magnesium

Explanation:

Mg(s) + 2CH3COOH(aq) -------> Mg(CH3COO)2(aq) + H2(g)

Since the reaction is 1:2 in mole ratio,

1 mole of magnesium reacts with 2 moles of ethanoic acid

x moles of magnesium will react with 0.2 moles of ethanoic acid

2x = 0.2

x = 0.2/2 = 0.1 moles of magnesium used

4 0

3 years ago

The tendency of an atom to pull electrons toward itself is referred to as its _____. ionic potential tonicity covalency electron

larisa86 [58]

Electronegativity

The tendency of an atom to pull electrons towards itself is called electronegativity.

It is the tendency of an atom to attract bonding pair of electrons towards itself. These atoms which are more electronegative are able to bear a negative charge and be stable.

Unlike electropositive elements which tend to lose electrons , electronegative elements hold on tightly to the electrons.

The electronegativity is measured using the Pauling Scale where the most electronegative element of the periodic table, Fluorine , is given a value of 4 and the rest of the elements have values lower than 4 according to the trends followed by their groups and periods.

The least electronegative element of the periodic table , Cesium has a value of 0.7 on the Pauling Scale.

Electronegativity increases when we move from left to right in the periodic table and it decreases (in general) when we move down the group.

(To know more about Electronegativity: https://brainly.in/question/5742635 )

4 0

1 year ago

News shows evidence of being plagiarized

mel-nik [20]

What this is??????????????????

7 0

3 years ago

What is the reason for attainment of equilibrium?

Shtirlitz [24]

Answer:

When a reversible reaction happens in a closed container, it reaches a dynamic equilibrium . At equilibrium: the forward and backward reactions are still happening. the forward and backward reactions have the same rate of reaction

Explanation:

4 0

3 years ago