chemistry class 9 chapter 1​

Answer:

the S.I unit

Explanation:

is the best unite

Answer:

A beam balance is an example of a first class lever.

Explanation:

A beam balance is an example of a first class lever. In a first class lever, the fulcrum is between the effort (force) and the load. The effort (force) moves over a large distance to move the load a smaller distance.

Other examples of first class lever are pliers, scissors, a crow bar, a claw hammer, a see-saw and a weighing balance etc.

Answer:

Narcotics

I think ans is

Explanation:

tropicaia

Ecstasy, also known as MDMA, is used recreationally, so it can be called a club drug. However, it is illegal in the US, so it would be considered a narcotic as well. The effects it has are also of the stimulant variety, so they would fall under that category as well. It is definitely not a depressant.

Answer:

Old and inefficient mining smokestacks contaminate the soils around abandoned mine sites.

Explanation:

A smokestack, is a very tall channel commonly used in many instances to release gases produced by combustion processes directly into the air. These high towers are aimed at dispersing the gaseous pollutants over a wider area thereby minimizing their impact.

Old and inefficient smokestack do not contaminate the soil since they are very high towers that discharge gases directly into the atmosphere. Hence they are not part of the sources of soil contamination in abandoned mines.

Answer:

this can helps you know the answer

Answer:

C.) The boiling point increases, and the freezing point decreases.

Explanation:

Answer:

1. Isotope 2 occurs most commonly

2. 39.02amu

Explanation:

1. Isotope 2 has a relative abundance of 78.68% i.e. 78.68 out of 100, hence, it is the isotope that occurs most commonly.

2. Isotope 1 = 9.67%, mass no: 38

Isotope 2 = 78.68%, mass no: 39

Isotope 3 = 11.34%, mass no: 40

Isotope 4 = 0.31%, mass no: 41

To find the average atomic mass of element X, we multiply each isotopes' relative abundance by its mass no and find the sum as follows:

We convert each percentage to decimal abundance:

Isotope 1 = 9.67% = 0.0967

Isotope 2 = 78.68% = 0.7868

Isotope 3 = 11.34% = 0.1134

Isotope 4 = 0.31% = 0.0031

(0.0967 × 38) + (0.7868 × 39) + (0.1134 × 40) + (0.0031 × 41)

3.6746 + 30.6852 + 4.536 + 0.1271

Average atomic mass = 39.02amu

0Answer: 0.6094

Explanation:

no of moles = mass / molar mass = 100/164.088= 0.6094 mole

Answer:

0.609 moles

Explanation:

mass in g ÷ atomic mass = moles

Ca(NO₃)₂ = 1 Ca 40.078 amu

2 N 28.0134 amu

+ 6 O 95.994 amu

____________________

164.0854 amu

100 g ÷ 164.0854 amu = 0.609 moles

three significant digits

Answer:

D. Microwave, Blue Visible Light, Ultraviolet, Gamma

Explanation:

colors longest to shortest are

red green blue violet

longest wavelength to shortest:

radio waves, microwaves, infrared, optical, ultraviolet, X-rays, and gamma-rays.

Answer:

C2H4O2 + 2O2 ==> 2CO2 + 2H2O

Explanation:

Start with the carbons

C2H4O2 + O2 ==> 2CO2 + H2O There are 2 on the left, so you need 2 on the right.

Next deal with the hydrogens. You have 4 on the left so you have to make 4 on the right

C2H4O2 + O2 ==> 2CO2 + 2H2O

The oxygens are the real devil in this question. Be careful how you handle them. There are 2 * 2 = 4 from the CO2 and 2*1 = 2 from the water. The total is 6

Now you can't just put a 3 in front of the O2. There are 2 in the given chemical. So you don't need 6. You need 6 -2 = 4. But the oxygen is O2. You have to divide the 4 by 2 to get 2

C2H4O2 + 2O2 ==> 2CO2 + 2H2O  

And that's your answer.

Explanation:

H2O water molecule

O3 Ozone

are some of common example of molecules

Answer:

its a chemical change.

hope it helps.

Answer: it is a chemical change because it involves chemical process

Explanation:

Answer:

that the water is blue because of the way water absorbs light, the way particles in the water scatter light, and also because some of the blue light from the sky is reflected

Answer:

In both voltaic and electrolytic cells, oxidation occurs at the anode, while reduction occurs at the cathode. Thus, both these cells exhibit redox reactions. In both these cells, electrons flow from the anode to the cathode through the externally connected conductor.

Answer:

ELECTROLYTIC CELL

An electrochemical cell in which a non-spontaneous chemical reaction takes place when electric current is passed through the solution,is called an electrolytic cell.

EXAMPLE

Nelsons cell and Downs cell

VOLTAIC CELL OR GALVANIC CELL

The electrochemical cell in which a spontaneous chemical reaction takes place and generates electric current is called galvanic and voltaic cell.

EXAMPLE

Daniel cell

Explanation:

Answer:

2.2 × 10⁻³ mol

Explanation:

Step 1: Calculate the number of equivalents in 0.50 L of blood

The blood calcium level of 8.8 meq/L.

0.50 L Blood × 8.8 meq/L = 4.4 meq = 4.4 × 10⁻³ eq

Step 2: Calculate the number of moles of calcium

Calcium has a charge of 2. Thus, it has 2 equivalents per mole.

4.4 × 10⁻³ eq × 1 mol/2 eq = 2.2 × 10⁻³ mol

Answer:

B

Explanation:

4.8×10^-4

10^-4 = 0.0001

4.8×0.0001 = 0.00048

Answer:

55.768

Explanation:

The following information is given in this question:

Fe-54 = 5.845%

Fe-56 = 91.754%

Fe-58 = 2.119%

First, we convert from percentage abundance to decimal abundance

Fe-54 = 5.845% = 0.05845

Fe-56 = 91.754% = 0.91754

Fe-58 = 2.119% = 0.02119

To find the average atomic mass of iron (Fe), we multiply each isotopes' decimal abundance by its mass no and find the sum as follows:

Average atomic mass = (0.05845 × 54) + (0.91754 × 56) + (0.02119 × 58)

Average atomic mass = 3.1563 + 51.38224 + 1.22902

Average atomic mass = 55.768

Answer:

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Answer:

There is 7642 grams of CO2 released

Explanation:

Step 1: Data given

carbon dioxide = CO2

Molar mass of carbon dioxide = 44.01 g/mol

Mass of ethanol = 4 kg = 4000 grams

Molar mass of ethanol = 46.07 g/mol

Step 2: The reaction

Combustion of ethanol means there is oxygen (O2) added. The products are CO2 and H2O.

C2H5OH + 3O2 → 2CO2 + 3H2O

Step 3: Calculate number of moles of ethanol

Moles ethanol = mass ethanol / molar mass ethanol

Moles ethanol = 4000 grams / 46.07 g/mol

Moles ethanol = 86.82 moles

Step 4: Calculate number of moles CO2

For 1 mol ethanol we need 3 moles to produce 2 moles CO2 and 3 moles H2O

For 86.82 moles of ethanol we'll have 2*86.82 = 173.64 moles CO2

Step 5: Calculate mass of CO2

Mass CO2 = moles CO2 * molar mass CO2

Mass CO2 = 173.64 moles * 44.01 g/mol

Mass CO2 = 7642 grams

There is 7642 grams of CO2 released

Answer:

This answer I think it is Al,F

Answer:

metro= 22g

Explanation:

Answer:

a. 1 cm^3 = 1 mL

explanation:

Answer:

B

Explanation:

because protons have a +1 charge and electrons have a -1 charge, so if an atom is neutral it must have the same amount of protons and neutrons

Answer: The report prepared is a nontestimonial hearsay.

Explanation:

The nontestimonial hearsay can be defined as the expert opinion or statement given casually and not for the purpose of keeping or considering it as record by the government agent or agency. Here the given conclusion provided by the chemical expert is an example of nontestimonial hearsay because it is not the output of experimental and analytical procedures instead it is a casual opinion. Testimonial hearsay include the evidences that are based on detailed and thorough analytic procedures.

[tex]\huge\boxed{\fcolorbox{red}{blue}{ QUESTION }}[/tex]

The maximum number of electrons that can be present in an shell is

[tex] \orange{\underline{\huge{\bold{\textit{\green{\bf{OPTIONS}}}}}}} [/tex]

a) [tex]2 {n}^{2} [/tex]

b) [tex]2 {n}^{2} + 1[/tex]

c) 2n

d) none of these.

[tex] \huge\mathbb{\red A \pink{N}\purple{S} \blue{W} \orange{ER}}[/tex]

OPTION (a)

[tex]2 {n}^{2} [/tex]

[tex] \bold { \red{ \star{ \blue{EXAMPLES}}}}[/tex]

In First shell only 2 electron can be placed .

[tex]2 {n}^{2} \\ n = 1 \: (bez \: \: no \: \: shell \: = 1) \\ so \\ 2 { n}^{2} = 2 \times {1}^{2} = 2 \: electrons[/tex]

In second shell 8 electrons can be placed

[tex]2 {n}^{2} \\ n = 1(bez \: \: no\: \: shell \: = 2) \\ 2 {n}^{2} = 2 \times {2}^{2} = 2 \times 4 = 8 \: electrons[/tex]

Answer:

uh i think this is the answer

Explanation:

Answer:

En el grupo de los no metales se incluyen los halógenos​ (flúor, cloro, bromo, yodo, astato y téneso), que tienen 7 electrones en su última capa de valencia y los gases nobles (helio, neón, argón, kriptón, xenón, radón), que tienen 8 electrones en su última capa (excepto el helio, que tiene 2).

Explanation:

halógenos

Answer:

1,4

Explanation:

Answer:

C

Explanation:

like charges repel each others so if they have the same charge they will move away from each other

Answer:

1 gramo de metano aporta 50.125 kilojoules.

1 gramo de metano aporta 48.246 kilojoules.

Explanation:

La cantidad de energía liberada por la combustión de una unidad de masa del hidrocarburo ([tex]Q[/tex]), en kilojoules por mol, es igual a la cantidad de energía liberada por mol de compuesto ([tex]\bar {Q}[/tex]), en kilojoules por mol, dividido por su masa molar ([tex]M[/tex]), en gramos por mol:

[tex]Q = \frac{\bar Q}{M}[/tex] (1)

A continuación, analizamos cada caso:

Metano

[tex]Q = \frac{802\,\frac{kJ}{mol} }{16\,\frac{g}{mol} }[/tex]

[tex]Q = 50.125\,\frac{kJ}{g}[/tex]

1 gramo de metano aporta 50.125 kilojoules.

Octano

[tex]Q = \frac{5500\,\frac{kJ}{mol} }{114\,\frac{g}{mol} }[/tex]

[tex]Q = 48.246\,\frac{kJ}{mol}[/tex]

1 gramo de metano aporta 48.246 kilojoules.

Answer:

•cocoons are boiled in hot water for obtaining silk fibres from cocoons.

•camel wool considered a natural health product because it has excellent thermal proities

Answer:

volcanic eruption caused by plate tectonics.

Explanation:

Constructive process is one in which memories are influenced by some events. When a person tries to retrieve the memory he first click some event which is associated with that memory and then whole flash backs comes to his mind.