Is lead a mixture or pure substance? and is Paint a mixture or pure substance?

Answer:

D: 100 cm = 1 m

Explanation:

she needs to know how many cm are in a meter

The first element to have 4d electrons in its electron configuration is yttrium (Y).

In the periodic table, the first element to have 4d electrons in its electron configuration is the transition metal yttrium (Y).

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The correct answer is A.Enzymes reduce the activation energy of the transition state. I just did it. Enzymes are catalysts and will lower activation energy.

Enzymes reduces the activation energy of the transition state is the statement that describes the mechanism of an enzyme.

Enzymes are catalysts and act on molecules known as substrates and allow the development of various cellular processes.

Its function is to help accelerate chemical reactions, this means that the reaction under the control of an enzyme reaches its equilibrium much faster than a non-catalyzed reaction.

Enzymes work by lowering the activation energy of a chemical reaction, that is, the amount of energy needed to start it.

They are especially effective catalysts, since they lower the activation energy to even more than inorganic catalysts.

Therefore, we can conclude that enzymes are regulatory substances in the body of living things, usually decreasing the initial energy required to start the reaction.

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According to the electronic configuration, group 18 elements have eight valence electrons in the ground state.

Electronic configuration is defined as the distribution of electrons which are present in an atom or molecule in atomic or molecular orbitals.It describes how each electron moves independently in an orbital.

Knowledge of electronic configuration is necessary for understanding the structure of periodic table.It helps in understanding the chemical properties of elements.

Elements undergo chemical reactions in order to achieve stability. Main group elements obey the octet rule in their electronic configuration while the transition elements follow the 18 electron rule. Noble elements have valence shell complete in ground state and hence are said to be stable.

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The key is the heat of fusion: 7.27 kJ is released for each mole of diethyl ether that freezes at its freezing point. 2950 g (C2H5)2O x (1 mol (C2H5)2O / 74.0g (C2H5)2O) x (7.27 kJ / 1 mol (C2H5)2O) = 290. kJ

Heat of fusion = 7.27kJ/mol

1.25x[tex]10^9[/tex] years old a rock that contains equal amounts of potassium-40 and argon-40.

Half-life is the time taken for the radioactivity of a substance which is half to its original value.

The half-life of potassium-40 is about  1.25x[tex]10^9[/tex], or 1.25 billion, years. it undergoes beta decay and becomes argon-40. Equal amounts would be one half-life, so the sample is also 1.25x[tex]10^9[/tex] years old.

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The Theoretical Yield of Magnesium Oxide is 3.55 grams

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Final answer:

The position of an element on the periodic table can predict its valence electrons, chemical reactivity, and whether it's a metal, non-metal, or metalloid. Trends like atomic radius, ionization energy, and electron affinity also correspond to an element's location on the table, allowing for prediction of properties of elements like Francium based on their group.

Explanation:

Predictions Based on the Periodic Table:

The periodic table is a powerful tool that organizes elements by increasing atomic number and groups them based on similar properties. By examining an element's position on the periodic table, we can predict a range of its characteristics.

Group and Period Trends:

Elements in the same group (vertical column) share the same number of valence electrons and tend to display similar chemical behaviors, such as their reactivity and bonding patterns. The position of an element also indicates whether it is a metal, non-metal, or metalloid, with metals typically located on the left side, non-metals on the far right, and metalloids along the zig-zag line separating metals and non-metals.

Periodicity Properties:

Specific trends can be observed as we look horizontally across periods or vertically down groups. Metallurgical traits generally increase as one moves down a group. Furthermore, other properties such as atomic radius, ionization energies, and electron affinities change in a predictable manner across periods and down groups.

Given an element like Francium (Fr), for instance, we can predict its electronic structure, lower ionization energy compared to its predecessor in the group, and even relative melting and boiling points based on its position in group 1. As such, the periodic table not only reflects the elemental order but also serves as a map to infer various attribute trends.

The balanced equation for the reaction of sodium metal with water is 2Na (s) + 2H₂O (l) → 2NaOH (aq) + H₂ (g), where sodium and water react to form sodium hydroxide and hydrogen gas.

The balanced chemical equation for the reaction of sodium metal with water to form aqueous sodium hydroxide and hydrogen gas is:

2Na (s) + 2H₂O (l) → 2NaOH (aq) + H₂ (g)

This equation indicates that two moles of solid sodium (Na) react with two moles of liquid water (H₂O) to produce two moles of aqueous sodium hydroxide (NaOH) and one mole of molecular hydrogen gas (H₂). It is important to note that hydrogen gas is always produced as diatomic molecules, hence H₂(g), not H(g).

Upon dissolving in water, sodium hydroxide disassociates into sodium ions (Na+) and hydroxide ions (OH−), increasing the concentration of OH− ions in the solution, making it a strong base.

Answer:

A) thrust equal to its resistance.

Explanation:

This might help.

The average atomic mass of rubidium is 85.466 amu.

For calculating the average atomic mass of the Rb, the atomic masses for both the isotopes are taken into consideration.

The [tex]\rm ^8^5Rb[/tex] has atomic mass = 84.912 amu

The abundance of [tex]\rm ^8^5Rb[/tex] = 72.17 %

The average atomic mass of [tex]\rm ^8^5Rb[/tex] = 84.912 [tex]\rm \times\;\dfrac{72.17}{100}[/tex]

= 61.28 amu

The [tex]\rm ^8^7Rb[/tex] has atomic mass = 86.909 amu

The abundance of [tex]\rm ^8^7Rb[/tex] = 27.83%

The average atomic mass of [tex]\rm ^8^7Rb[/tex] = 86.909 [tex]\rm \times\;\dfrac{27.83}{100}[/tex]

= 24.186 amu

The average atomic mass of Rb will be = [tex]\rm ^8^5Rb[/tex] + [tex]\rm ^8^7Rb[/tex]

= 61.28 + 24.186 amu

= 85.466 amu.

The average atomic mass of rubidium is 85.466 amu.

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Answer:

Mass: 981.0 g

Density: 5.61 g/cm^3

Hardness: 2.5-3

Unknown Mineral: chalcocite

The Mohs scale of mineral hardness is a qualitative scale used to determine the hardness of minerals.

The Mohs scale of mineral hardness is a qualitative scale developed by Frederich Mohs in 1822. It is used to determine the hardness of minerals based on their ability to resist scratching or abrasion. The scale consists of 10 minerals, with diamond being the hardest mineral with a rating of 10. By comparing the unknown mineral's hardness to the minerals on the scale, we can identify the unknown mineral.

Final answer:

Covalent compounds have low melting and boiling points and do not conduct electricity. Ionic compounds form hard crystalline solids with high melting points and can conduct electricity when molten or dissolved in water.

Explanation:

Covalent compounds, also known as molecular compounds, display a wide range of physical properties compared to ionic compounds. Covalent compounds consist of discrete molecules held together by weak intermolecular forces, allowing them to exist as gases, liquids, or solids at room temperature and pressure. They have low melting and boiling points compared to ionic compounds due to the weaker forces between molecules. Additionally, covalent compounds do not conduct electricity in any state.

On the other hand, ionic compounds form hard crystalline solids with high melting points. They are composed of ions held together by strong ionic bonds. Although ionic compounds do not conduct electricity in the solid state, they can conduct well when molten or dissolved in water. Additionally, most ionic compounds are soluble in water.

Final answer:

The formula weight of calcium nitrate, Ca(NO3)2, is calculated by summing the weights of one calcium atom, two nitrogen atoms, and six oxygen atoms, resulting in a weight of 164.08 amu which, rounded to one decimal place, is 164.1 amu.

Explanation:

The formula weight of calcium nitrate, Ca(NO3)2, is calculated by adding up the atomic weights of all the atoms in its formula. The calcium atom contributes 40.08 amu, each nitrogen atom contributes 14.00 amu, and each oxygen atom contributes 16.00 amu. Since there are two nitrate ions in the formula (indicated by the subscript 2), you must account for two nitrogen atoms and six oxygen atoms. The detailed calculation is as follows:

Adding these contributions together gives:

40.08 amu (Ca) + 28.00 amu (N) + 96.00 amu (O) = 164.08 amu

Therefore, when rounded to one decimal place, the formula weight of calcium nitrate is 164.1 amu.

The atom with atomic number 12 and mass number 25 contains 12 protons and 13 neutrons, making it most likely an isotope of magnesium.

An atom with an atomic number of 12 and a mass number of 25 can best be described by option (a): an atom that contains 12 protons and 13 neutrons. The atomic number represents the number of protons in the nucleus of the atom, which is 12 in this case. Since the mass number is the sum of protons and neutrons, we subtract the number of protons (12) from the mass number (25) to find that there are 13 neutrons. The atom described is likely an isotope of magnesium, as magnesium has an atomic number of 12.

Final answer:

Physiological saline used in IV solutions contains 9 grams of NaCl per liter of solution (0.9% NaCl), standard as normal saline, and has an osmolarity of about 300 mOsm/L. Ringer's lactate additionally contains potassium, calcium, and lactate ions. These solutions are isotonic with body fluids to prevent cell damage and maintain proper cellular function.

Explanation:

Physiological saline, commonly used for intravenous drips in medical settings, has an ionic composition that is similar to that of the blood's plasma to ensure compatibility with the body. The standard saline solution, known as normal saline, is a sterile mixture of sodium chloride (NaCl) dissolved in water, with a concentration of 9 grams per liter. This makes the solution 0.9% NaCl, which is isotonic to the body's fluids.

The osmolarity of normal saline is roughly 300 milliosmoles per liter (mOsm/L), closely mirroring the osmolarity of bodily fluids. Another common IV solution is Ringer's lactate, which includes not only sodium and chloride ions but also small amounts of potassium, calcium, and lactate. The lactate works as a buffer and is metabolized by the liver into bicarbonate, aiding in maintaining blood's acid-base balance.

The importance of isotonic solutions like normal saline and lactated Ringer's solution cannot be overstated; they ensure that water does not shift rapidly into or out of the body's cells, which could potentially cause cell damage or dysfunction.

When preparing an IV solution for a patient with specific needs, such as hypokalemia, a different concentration of electrolytes may be required, such as a 0.5% KCl solution. This requires careful preparation, often following a physician's orders, to match the patient's physiological conditions as closely as possible.