True/False: There are about 400 known elements

Answer:

13.25 ×10²³ atoms

Explanation:

Given data:

Mass of NaCl = 128 g

Number of atoms = ?

Solution:

First of all we will calculate the number of moles of NaCl.

Number of moles = mass/molar mass

Number of moles = 128 g/ 58.4 g/mol

Number of moles = 2.2 mol

Number of atoms:

1 mole of any substance contain 6.022×10²³ atoms.

2.2 mol × 6.022×10²³ atoms / 1mol

13.25 ×10²³ atoms

Answer:

a rotating disk of dust and gases

Explanation:

brainliest?

Answer:  scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star (called a supernova). ... Squeezing made the cloud start to collapse, as gravity pulled the gas and dust together, forming a solar nebula.

Explanation:

B. The partial pressure of N2 is 101 kPa

Given

volume = 22.4 L

1.0 mol of nitrogen and 2.0 mol of hydrogen at 0°C

Required

Total pressure and partial pressure

Solution

Ideal gas law :

PV = nRT

n total = 3 mol

T = O °C + 273 = 273 K

P = nRT/V

P = 3 x 0.08205 x 273 / 22.4

P total = 3 atm = 303,975 kPa

P Nitrogen = 1/3 x 303.975 = 101.325 kPa

P Hydrogen = 2/3 x 303.975 = 202.65 kPa

Answer:The partial pressure of N2 is 101 kPa

Explanation:

Answer:

1. definition of a problem

2.solution to the problem

3.the result

Explanation:

Hope this helps

The three (3) must haves of a hypothesis include the following;

A hypothesis can be defined as a testable explanation for an  observation or a scientific problem. Thus, a hypothesis is a type of statement that is typically considered to be either tentative or an educated guess.

An example of a hypothesis is saying;

Generally, the three (3) must haves of a hypothesis include the following;

1. A hypothesis must be tested and falsifiable.

2. A hypothesis must be supported by an observation and results of control experiments.

3. A hypothesis must proffer a solution to a problem.

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Answer:

A. wearing sunglasses to to protect eyes from UV rays

Explanation:

Your eyes are outside of your body, meaning external. All the other choices deal with internal organs.

Answer:

it's the electron cloud model

Answer:

C. 5 inches

Explanation:

don't worried, i learned that from my teacher

Answer: b

Explanation: had the same question

Answer:

Explanation:

mass of one atom of helium-4 is one-third the mass of one atom of carbon-12. You can find ... mass He. 1 mole He. 4.00 g He. -= 0.366 g He. 0.0914 mothé x 1 motte. Helium ... How many moles of oxygen atoms are present in 5.00 mol diphos-.

Answer:

Pure Water.

Explanation:

Pure water evaporates faster than salt water.

Answer:

Carbon dioxide

Explanation:

that's all I can say

Answer:

Its C. Please mark me brainliest if this helped

Answer:

Question:

A spring with a spring constant of 30 N/m is stretched 0.2 m from its equilibrium position. How much work must be done to stretch it an additional 0.1 m?

Elastic Potential Energy:

The work that needs to be done by any object is a form of energy. The work can be defined in terms of the work-energy theorem, which states that the work can either be the difference in the kinetic energy of a system or the difference in the potential energy of a system. There is a special type of potential energy reserved exclusively for

Answer:

People wanted to settle there because it had good living conditions. There was rich soil, and lots of water sources.

I hope this helps!

The volume of dry gas = 168 L

Given

175 ml container at 15°C

P total = 752 torr

water vapour = 12.8 torr

Required

The volume of dry gas

Solution

Dalton's law of partial pressure :

P tot = P₁ + P₂ + P₃ ....  

P total = P O2 + P water

P O2 = 752 - 12.8

P O2 = 739.2 torr

Boyle's Law  

At a fixed temperature, the gas volume is inversely proportional to the pressure applied  

P₁V₁ = P₂V₂

739.2 175 = 770 .V₂

V₂ = 168 L

Answer: The nucleus is often referred to as the control center, or brain, of the cell and contains the DNA, or genetic material. The nucleus is surrounded by the nuclear envelope. ... Human cells are eukaryotic cells.

Explanation:

Answer:

Nucleus

Explanation:

not to good at explaining but I'm hoping this is right!

Answer:

Chromium is a chemical element with symbol Cr and atomic number 24. Classified as a transition metal, Chromium is a solid at room temperature

Explanation:

Hope it help

Mark me as brainliest

THANKS

Answer:

the periodic table is important because it is organized to provide a alot of information about elements and how they relate to one another in one easy-to-use reference. The table can be used to predict the properties of elements, even those that have not yet been discovered.

Explanation:

Answer:

The answer is C: “sunlight in deeper locations decrease”

Explanation:

C is the answer because the more salinity water has.. the harder it is to see and the harder it is for light to travel through the ocean.

Answer:

c

Explanation:

Answer: 80

Explanation:

12+6+1+1=20

20x4=80

Answer:

9.5 m

Explanation:

First, divide 4.75 m by the 0.50 l

4.75/0.50

This leaves you with 9.5 m

Answer:

Mercury

Explanation: Under standard conditions mercury is a shiny, heavy, silvery liquid. It is the only metal that is liquid at room temperature.

Answer:

Mercury, Venus, earth and mar, Jupiter, Saturn, urines, Neptune.

Explanation:

Answer:

c they are all made of cells

Explanation:

that's the only similarity

Answer:

B) C3H3O and C6H6O2

Explanation:

Given data:

Molar mass of compound = 100 g/mol

Percentage of hydrogen = 5.45%

Percentage of carbon = 65.45%

Percentage of oxygen = 29.09%

Empirical formula = ?

Molecular formula = ?

Solution:

Number of gram atoms of H = 5.45 / 1.01 = 5.4

Number of gram atoms of O = 29.09/ 16 = 1.8

Number of gram atoms of C = 65.45 / 12 = 5.5

Atomic ratio:

            C                      :      H            :         O

           5.5/1.8              :     5.4/1.8     :        1.8/1.8

            3                      :        3          :        1

C : H : O = 3 : 3 : 1

Empirical formula is C₃H₃O.

Molecular formula:

Molecular formula = n (empirical formula)

n = molar mass of compound / empirical formula mass

Empirical formula mass = 12×3 + 1.01 ×3 + 16×1 = 55.03  

n = 100 / 5503

n = 2

Molecular formula = n (empirical formula)

Molecular formula = 2 (C₃H₃O)

Molecular formula = C₆H₆O₂

Work done : 19.5 J

Given

F = 15 N

d = 1.3 m

m = 3 kg

Required

Work done

Solution

Work is the product of force with the displacement of objects.  

Can be formulated  

W = F x d  

W = Work, J, Nm  

F = Force, N  

d = distance, m  

Input the value :

W = 15 N x 1.3 m

W = 19.5 J

the mass has no effect on this problem

Answer:Na2O

Explanation:

When sodium  and oxygen combine, the resulting  chemical formula will be Na₂O.

Chemical  formula is a way of representing the number of atoms present in a compound or molecule.It is written with the help of symbols  of elements. It also makes use of brackets and subscripts.

Subscripts are used to denote number of atoms of each element and brackets indicate presence of group of atoms. Chemical formula does not contain words. Chemical formula in the simplest form  is called empirical formula.

It is not the same as structural formula and does not have any information regarding structure.It does not provide any information regarding structure of molecule as obtained in structural formula.

There are four types of chemical formula:

1)empirical formula

2) structural formula

3)condensed formula

4)molecular formula

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