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3 years ago

A chemical reaction takes place to allow hand warmers to give off heat. This is an example of a(n) __________.

Chemistry

2 answers:

Dvinal [7]3 years ago

8 0

Answer:

Explanation:

Gives off heat,.

Sphinxa [80]3 years ago

3 0

Answer:

Exothermic

Explanation:

Exothermic reactions release heat, endothermic absorb heat, and precipitate is a solid formed from a solution

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Consider the following weak acids and their Ka values: Acetic Acid Ka = 1.8×10^−5 Phosphoric Acid Ka = 7.5×10^−3 Hypochlorous Ac

vfiekz [6]

Answer:

a. Phosphoric Acid

b. Acetic Acid

c. Hypochlorous Acid

Explanation:

A buffer works when the pH of this one is in pKa ± 1. That means, to find which buffer system works in some pH you need to find pKa:

pKa = -log Ka

pKa Acetic acid:

-log1.8x10⁻⁵ = 4.74

pKa phosphoric acid:

-log7.5x10⁻³ = 2.12

pKa hypochlorous acid:

-log3.5x10⁻⁸ = 7.46

a. For a pH of 2.8 the best choice is phophoric acid because its effective range is: 1.12 - 3.12 and 2.8 is between these values.

b. pH 4.5. Acetic acid. effective between pH's 3.74 - 5.74

c. pH 7.5. Hypochlorous acid that works between 6.46 and 8.46

7 0

3 years ago

mixture of N 2 And H2 Gases weighs 13.22 g and occupies a volume of 24.62 L at 300 K and 1.00 atm.Calculate the mass percent of

anygoal [31]

Answer: The mass percent of nitrogen gas and hydrogen gas is 91.41 % and 8.59 % respectively.

Explanation:

To calculate the number of moles, we use the equation given by ideal gas equation:

PV = nRT

where,

P = Pressure of the gaseous mixture = 1.00 atm

V = Volume of the gaseous mixture = 24.62 L

n = number of moles of the gaseous mixture = ?

R = Gas constant = $0.0821\text{ L atm }mol^{-1}K^{-1}$

T = Temperature of the gaseous mixture = 300 K

Putting values in above equation, we get:

$1.00atm\times 24.62L=n_{mix}\times 0.0821\text{ L atm }mol^{-1}K^{-1}\times 300K\\\\n_{mix}=\frac{1.00\times 24.62}{0.0821\times 300}=0.9996mol$

We are given:

Total mass of the mixture = 13.22 grams

Let the mass of nitrogen gas be 'x' grams and that of hydrogen gas be '(13.22 - x)' grams

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

For nitrogen gas:

Molar mass of nitrogen gas = 28 g/mol

$\text{Moles of nitrogen gas}=\frac{x}{28}mol$

For hydrogen gas:

Molar mass of hydrogen gas = 2 g/mol

$\text{Moles of hydrogen gas}=\frac{(13.22-x)}{2}mol$

Equating the moles of the individual gases to the moles of mixture:

$0.9996=\frac{x}{28}+\frac{(13.22-x)}{2}\\\\x=12.084g$

To calculate the mass percentage of substance in mixture we use the equation:

$\text{Mass percent of substance}=\frac{\text{Mass of substance}}{\text{Mass of mixture}}\times 100$

Mass of the mixture = 13.22 g

For nitrogen gas:

Mass of nitrogen gas = x = 12.084 g

Putting values in above equation, we get:

$\text{Mass percent of nitrogen gas}=\frac{12.084g}{13.22g}\times 100=91.41\%$

For hydrogen gas:

Mass of hydrogen gas = (13.22 - x) = (13.22 - 12.084) g = 1.136 g

Putting values in above equation, we get:

$\text{Mass percent of hydrogen gas}=\frac{1.136g}{13.22g}\times 100=8.59\%$

Hence, the mass percent of nitrogen gas and hydrogen gas is 91.41 % and 8.59 % respectively.

5 0

3 years ago

16. As he developed his periodic table, Mendeleev grouped the elements lithium,

Aleonysh [2.5K]

Answer:

the reactivity and the valence electrons

Explanation:

the reactivity of the elements would have played a significant role in why such elements were grouped together. the number of valence electrons dictates how reactive an element is - the less valence electrons the more reactive it is. the column, group 1 in which these elements are put together in, show that each of the elements have 1 valence electrons and are therefore reactive.

you can go on to further explain what valence electrons are, explain what the group numbers are associated with the valence electrons and how valence electrons effect reactivity. further this, talk about how the three elements have the same number of valence electrons and therefore were grouped together

8 0

3 years ago

Easy one! giving brainly if correct

Dafna1 [17]

Answer: glass is not considered as solute.

Extra's:

A solute is a substance that gets dissolved in a solvent. ... The solutes in air are oxygen, argon, and carbon dioxide gas, as well as water vapour.

Sugar is a solute in the solvent water. Sugar is one of the most soluble solutes in water.

Also solute is a powder that can be dissolved in solvent like water. here baking soda is a solute.

5 0

3 years ago

The following is an example of which type of boundary?

kow [346]

I believe that it most likely would be D.

8 0

3 years ago