Which elements from the periodic table are the least reactive?
A noble gases
B transition metals
C lanthanides
Dmetalloids

Answer:

Caesium (55Cs) has 40 known isotopes, making it, along with barium and mercury, one of the elements with the most isotopes. The atomic masses of these isotopes range from 112 to 151. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 2.3 million years, ... It constitutes most of the radioactivity still left from the Chernobyl accident ...

The enthalpy of combustion per mole is -5397.7 kJ/mol.

The term combustion refers to a reaction in which  a substance is burnt in oxygen. Now we know that octane is a hydrocarbon and its combustion follows the general equation for the combustion of hydrocarbons.

[tex]2C_{8}H_{18} (g) + 25O_{2} (g)---- > 16CO_{2} (g) + 18H_{2} O(g)[/tex]

Given that the number of moles in one gram of octane is obtained from;

1g/114 g/mol = 0.0088 moles

If the burning of 0.0088 moles of octane produces  -47.5 kJ

Burning of 1 mole of octane would produce  1 mole * -47.5 kJ/0.0088 moles

= -5397.7 kJ/mol

We can now write is as;

[tex]2C_{8}H_{18} (g) + 25O_{2} (g)---- > 16CO_{2} (g) + 18H_{2} O(g)[/tex] ΔH = -5397.7 kJ/mol

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Answer:The formula for molality is m = moles of solute / kilograms of solvent.

Explanation:

Answer:  C. 6

Explanation:

According to the Law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

The balanced chemical reaction for photosynthesis is :

[tex]C_6H_{12}O_6+6O_2\rightarrow 6CO_2+6H_2O+energy[/tex]

Thus the coefficient of water is 6.

Answer:

Both the initial and final substances are composed of atoms because all matter is composed of atoms. According to the law of conservation of matter, matter is neither created nor destroyed, so we must have the same number and type of atoms after the chemical change as were present before the chemical change.

Explanation:

The atoms that make up your body were produced inside a star and have ... I read once that atoms get recycled so much through the planet that each of ... from William Shakespeare, but I do know this: All of us come from stars. ... If you have gold fillings in your teeth, those atoms came from a star explosion.

Answer:

I know the answer, but it is hard to explain

Explanation:

yIt easy u but the single letter in the outside boxes. Then u but the one in the middle box. But the BB in one corner. then but bb on the opposite corner. Then but Bb on the other box.

Answer:

father.....Bb

mother.....bb

offspring, 50%Bb brown eyes ,50%bb blue eyes

Answer:

potassium hydroxide test

Explanation:

The test that uses color change to reveal oil-based paints is the potassium hydroxide test. The correct option is c.

The KOH (potassium hydroxide) approach is used to test for yeast in specimens. Potassium hydroxide acts as an enzymatic agent, breaking down detritus in a specimen, such as epithelial cells and WBCs, allowing yeast or pseudohyphae to be seen.

The potassium hydroxide prep test is used to detect fungal diseases on the skin or in the nails. A scrape of cells from the afflicted area is examined under a microscope for evidence of fungus. The potassium hydroxide skin lesions exam, fungal smear, or skin scraping are other names for the potassium hydroxide test.

Therefore, the correct option is the c, potassium hydroxide test.

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Answer:

thermal conductivity: the rate at which heat is transferred by conduction through a unit cross-section area of a material, when a temperature gradient exits perpendicular to the area

electrical conductivity: the measure of the amount of electrical current a material can carry or it's ability to carry a current

solubility: the ability to be dissolved, especially in water

magnetism: a physical phenomenon produced by the motion of electric charge, resulting in attractive and repulsive forces between objects

melting point: the temperature at which a given solid will melt.

boiling point: the temperature at which a liquid boils and turns to vapor

Explanation:

hope this helps :D pls mark brainliest :D

We will need to know Avogadro's number and the molar mass of sucrose for this problem to do dimensional analysis.

250g × [tex]\frac{1 mol}{342.297g}[/tex] × [tex]\frac{6.022 * 10^{23} molecules}{1 mol}[/tex] = 4.398 molecules

There are 4.398 sucrose molecules in 250 grams of sucrose.

Answer:

See the answer below

Explanation:

From the equation, 1 mole of C requires 1 mole of O2 for a balanced reaction.

1 g of C will not exactly react with 1 g of O2 because the 1 g of each of the reactants contain different amounts of the substance.

The amount (in moles) of a substance is the mass of that substance divided by the molar mass.

Hence, 1 g of C will contain 1/12 moles of the substance while 1 g of O2 will contain 1/32 moles of the substance.

Answer:

there are two atoms

1. hydrogen

2.and water

Answer:

[tex]\boxed {\boxed {\sf 6.26 \times 10^{24} \ atoms }}[/tex]

Explanation:

To convert from moles to atoms, we must use a number called Avogadro's Number which is:

[tex]6.022\times10^{23}[/tex]

This number tells us the amount of atoms in a mole.

[tex]1 \ mole = 6.022\times10^{23} \ atoms[/tex]

To convert from moles to atoms, we must multiply Avogadro's number by the amount of moles.

We know there are 10.4 moles of Chlorine. Multiply 10.4 (molar amount) by 6.022 * 10²³ (Avogadro's Number)

[tex]10.4 \ mol *\frac{6.022\times10^{23} \ atoms }{ 1 \ mole}[/tex]

[tex]10.4 * 6.022\times10^{23} \ atoms[/tex]

[tex]1 \ mole = 6.022\times10^{23} \ atoms[/tex]

[tex]6.26288 \times 10^{24} \ atoms[/tex]

Let's round to 3 significant figures, because the original measurement 10.4, has 3 sig figs (1, 0, and 4)

For the number 6.26288, 3 significant figures is the hundredths place. The 2 in the thousandth place tells us to keep the 6 in the hundredths place.

[tex]6.26 \times 10^{24} \ atoms[/tex]

There are about 6.26 × 10²⁴ atoms in 10.4 moles of chlorine.

The mole fraction of 195 g AlCl3 in 240 mL of water is 0.099.

Mole fraction is the ratio of the number of moles of a particular component to the total number of moles in the mixture. To determine the mole fraction of AlCl3, the mass of AlCl3 will be converted to moles and the number of moles of water must be determined. Since the amount of water used is expressed in volume, we will be using the density of water to determine the mass of water for a given volume.

Solving for the moles of AlCl3:

moles AlCl3 = mass AlCl3 / molar mass of AlCl3

moles AlCl3 = 195 g / 133.33 g/mol

moles AlCl3 = 1.4625 mol

Solving for moles of water:

A commonly used density of water is 1 g/mL.

240 mL of water * (1 g/mL) = 240 g of water

moles water = mass water / molar mass water

moles water = 240 g / 18.02 g/mol

moles water = 13.32 mol of water

Mole fraction = mol AlCl3 / ( mol AlCl3 + mol water)

Mole fraction = 1.4625 / {1.4625 +13.32)

Mole fraction of AlCl3 is 0.099

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Answer:

organic compounds are classified based on functoin group

Explanation:

functional group is part of molecule or compound that determine the properties of that molecule or compound.

In chemistry, organic compounds are substances that have a covalently linked carbon atom. These compounds are classified based on the functional group and structures.

Organic compounds are said to be the compounds that have the presence of the carbon atom/s linked to the other atoms including nitrogen, oxygen, and hydrogen through a covalent bond.

The organic compounds are classified based on their structures and functional groups attached to their side chains. The functional groups include alkynes, alkenes, alcohols, carbonyl, nitriles, amines, etc.

The compounds can also be categorized based on the open or closed chain structures that can be homocyclic or heterocyclic. Further, the compounds can be aromatic or alicyclic.

Therefore, organic compounds are classified based on their functional groups and structures.

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Answer: Oxygen - 18 atom contains 8 protons.

Explanation:

The number of protons is the same as the atomic number. In isotopes, only the neutrons vary, but the protons always remain the same.

Answer:

99.3%

Explanation:

The percent by mass of the solute can be expressed as:

And for this problem:

So to calculate the percent by mass first we need to calculate the mass of water, to do so we use its density (1 g/L):

Density water = mass water / volume

Now we have all the data required to calculate the % mass:

Answer: 14.3

Explanation:

Answer:

67.08 g

Explanation:

you firts write what u know

then u calculate the molar mass of the salt

then according to the formula mass= number of mols × molar mass you find the mass

m= mass

n= number of mol

M= molar mass i hope this helps

Answer:

Untreated water from rivers, lakes, ponds, springs, or streams is likely to contain unsafe levels of infectious microorganisms, and drinking it may cause illness.

Explanation:

Answer:

0

General Formulas and Concepts:

Chemistry - Atomic Structure

Explanation:

Step 1: Define

6 Protons

6 Neutrons

6 Electrons

Step 2: Determine charges

6 Protons = + 6 charge

6 Neutrons = 0 charge

6 Electrons = - 6 charge

Step 3: Determine overall charge

+6 + 0 + -6 = 0

Answer:  L element has greater atomic number.

Explanation:

The periodic table contains vertical columns called as groups and horizontal rows called as periods.

Period 3 contains 8 elements which are sodium, magnesium , aluminium , silicon , phosphorous , sulphur, chlorine and argon.

K element which belongs to group 13 is aluminium with atomic number of 13 . L element which belongs to group 15 is phosphorous with atomic number of 15.

Thus L element has greater atomic number.

Answer:

They work in unision

Explanation:

The skeletal system is the framework our muscular system is attached to. The muscular system also allows the bones to move through contracting and extending. Although both would be useless without the nervous which sends impulses that tell the muscles to contract and extend.

Answer:

The person above is correct!

Explanation:

It graded it 100%.

Electron configuration for manganese is [Ar]3d⁵4s² and electron configuration is the distribution of electrons of an atom or molecule

The electronic configuration of an element is a symbolic notation of the manner in which the electrons of its atoms are distributed over different atomic orbitals and atomic number of manganese is 25 then electronic configuration [Ar]3d⁵4s² manganese is a chemical element with the symbol Mn and it is a hard, brittle, silvery metal, often found in minerals in combination with iron and atomic mass is 55.93 and we write electronic configuration is 1s²2s²2p⁶3s²3p⁶4s²4d⁵ called as electronic configuration of  manganese

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Answer:

heterogenous mixture i believe.

Explanation:

Answer:

I only know 3 its 0 N because 10-8=2 and 2-2=0

Explanation        10-8=2 2-2=0

Answer:Accounting for the sizes of protons, neutrons, and electrons, most of the volume of an atom—greater than 99 percent—is, in fact, empty space. ... The electrons that surround all atoms are negatively charged and cause atoms to repel one another, preventing atoms from occupying the same space.

Explanation: hope this helped