Chemistry Problems

Litmus Paper and the Litmus Test

★Purple Litmus Paper: Purple at neutral pH, red below pH 4.5, blue above pH 8.3

★Blue Litmus Paper: Unchanged blue or sometimes purple at neutral pH, red below pH 4.5, blue above pH 8.3. Blue paper that doesn’t change color indicates the sample is a base.

★Red Litmus Paper: Unchanged red or sometimes purple at neutral pH, red below pH 4.5, blue above pH 8.3. Red litmus paper that doesn’t change color indicates the sample is an acid.

This litmus test uses red, blue, or purple litmus paper to determine whether a sample is acidic, basic, or neutral.

paper is pH paper treated with litmus dye. It can be blue, red, or purple and only changes to those colors. Sometimes people call all pH paper “litmus paper.” But, this is not correct. Many indicators find use as dyes in pH paper and they can change to other colors.

A mineral acid is an inorganic acid that dissociates in water to yield a hydrogen ion (H+ or proton) and conjugate base. Mineral acids are important in chemistry and industry because the group includes many useful bench acids. Also, many of these acids serve as feedstock for making both organic and inorganic chemicals.

with chemist man.

*Aqua_Regia_Facts*

IUPAC Name:
Nitric acid hydrochloride

Other Names:
Aqua regis,
Nitrohydrochloric acid

Chemical Formula:
HNO_3 + 3 HCl

Appearance:
Yellow, orange, or red fuming liquid

Density:
1.01–1.21 g/cm^3

Boiling Point:
108 °C (226°F, 381 K)

Solubility:
Miscible in water

with Chemist Man.

Matter changes form but not identity in a physical change. A chemical reaction occurs and a new product is formed in a chemical change.

Everything made of matter is a chemical. If it does not contain matter, it’s not a chemical.

What Is Chemical Energy?

Chemical energy is defined as the form of potential energy stored within atoms and molecules. Usually, it’s the energy stored within chemical bonds, but it’s also the energy of the electron arrangement of ions and atoms. Chemical energy is observed when a chemical reaction occurs or matter changes forms. Energy is either absorbed or released when chemical energy changes form as the result of a chemical change.

A chemical reaction is a process that changes the chemical identity of the starting materials.

Two atoms of the same element are not necessarily identical. They have the same number of protons, but the number of neutrons and electrons may differ.

Why Use 4 Significant Figures for Avogadro’s Number?

Although Avogadro’s Number is named for Avogadro, he did not invent or discover it.
Avogadro’s number (Avogadro’s constant) is the quantity of objects found in 1 mole of a sample. It is an exact number that is defined as 6.02214076×10^23 mol^−1. This is essentially the number of atoms in 12 grams of carbon-12.

However, for most chemistry calculations, you work with atomic masses, which are commonly reported using 4 significant figures.

When you perform calculations using significant figures, you use the smallest number of significant digits. So, if you are using a mass of carbon that is 12.01 grams/mole (4 significant figures), you use 6.022 x 1023 as Avogadro’s number (4 significant figures).

When you perform calculations using significant figures, you use the smallest number of significant digits. So, if you are using a mass of carbon that is 12.01 grams/mole (4 significant figures), you use 6.022 x 10^23 as Avogadro’s number (4 significant figures).

Although Avogadro’s Number is named for Avogadro, he did not invent or discover it.

It’s easy to calculate the mass in grams of a single water molecule using the periodic table and Avogadro’s number.

One mole of water has a mass of 18 grams and volume of 18 milliliters or 0.018 liters.

The mole is the S unit for quantity that is exactly 6.022 x 10^23 particles.

Calculate the mass of a single atom of any element by dividing the atomic mass by Avogadro’s number.

The number of atoms in a mole of atoms in 6.022×10^23.

The electrons are located in a cloud surrounding the protons and neutrons of the atomic nucleus.

A mineral is a natural inorganic solid with a defined chemical composition and crystal structure.

Quick comparison of metals vs nonmetals.

In chemistry, a reducing agent is a species that loses electrons to an oxidizing agent. The reducing agent becomes oxidized, while the oxidizing agent is reduced.

The term “redox” means reduction-oxidation. A redox reaction involve the transfer of electrons between two chemical species.

Entropy is a measure of the randomness or disorder of a system.

Its symbol is the capital letter S. Typical units are joules per kelvin (J/K).

Change in entropy can have a positive (more disordered) or negative (less disordered) value.

In the natural world, entropy tends to increase. According to the second law of thermodynamics, the entropy of a system only decreases if the entropy of another system increases.

The laws of thermodynamic describe the relationships between matter and energy under different conditions.

The law of conservation of energy states that energy is neither created nor destroyed, although it can change forms.

The law of conservation of mass states that matter is neither created nor destroyed, but can change forms. This applies to a system that is closed for matter and energy.

Structure of NaCl

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