Why should a science teacher know how to prepare stock solution

Answer:

0.23 g

Explanation:

From the question given above, the following data were obtained:

Mass of solution = 20.3 g

Percentage by mass of KCl = 1.14%

Mass of KCl =?

The mass of KCl in the solution can be obtained as follow:

Percentage by mass = mass of solute / mass of solution × 100

1.14% = mass of KCl / 20.3

Cross multiply

Mass of KCl = 1.14% × 20.3

Mass of KCl = 1.14/100 × 20.3

Mass of KCl = 0.0114 × 20.3

Mass of KCl = 0.23 g

Therefore, the mass of KCl in the solution is 0.23 g

Answer:

D. It predicts whether or not a reaction will be spontaneous.

Explanation:

What does Gibbs free energy (ΔG) predict? .

A. It predicts what the rate of the reaction will be. NO. ΔG is a thermodynamical parameter and it is not related to the kinetics of the reaction.

B. It predicts how high the activation energy is. NO. ΔG is a thermodynamical parameter and it is not related to the kinetics of the reaction.

C. It predicts if entropy will increase or decrease. NO. ΔG depends on the entropy but not the other way around.

D. It predicts whether or not a reaction will be spontaneous. YES. If ΔG < 0 the reaction is spontaneous and if ΔG > 0 the reaction is not spontaneous.

Answer:

63 g Al is required to react with 35 mL of 2.50 M hydrochloric acid

I'm sorry if it's wrong, I tried.

Explanation:

A diagram representing the levels of organization within an organism is X. The  level of organization is identified by X is tissue. Therefore, option 2 is correct.

The term "tissue" refers to a collection of cells or fluid that cooperate to carry out a particular function in the body. Examples of such cells include those found in the kidney, heart, or blood cells, which transport oxygen to and waste products away from the body's cells.

The Old French term tissue, which means "a ribbon, belt, or piece of woven stuff," is where the noun tissue originates. Tissue really means to "weave fabric strands" as a verb. Tissues are now thought of as the disposable paper used for packaging presents or blowing our noses.

They stand for a degree of cell differentiation and order in living things. The activities of tissues include respiration, digesting, and transportation. As a result, tissues are crucial for multicellular creatures.

Thus, option 2 is correct.

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Answer:

The answer you picked was right.

Explanation:

Answer:

Explanation:

so u can work out the amount of moles in FeO3 by doing mr of fe3o3 is 55.8*3+16*3=215.4

moles= mass/mr so you do 15.5g/215.4=0.0719 moles

then using 1 to 1 ratio so O2 moles is 0.0719

then use the equation mass=mole*mr

so 0.0719*16=1.15g

hope this make sense :)

Answer:

The graph shows a directly proportional relationship between volume and temperature and represents Charles' Law.

Explanation:

The relation between volume and temperature is given by :

Ideal gas law, PV = nRT

Where

P is pressure

V is volume

R is gas constant

T is temperature

As volume and temperature have direct relationship. Charles law states that there is a direct relationship between volume and temperature. The correct option is (a).

Answer:

Ammonium chloride

Explanation:

because is a salt which is highly soluble in water than potassium

Explanation: this is how to calculate pressure underwater, I'm not sure if it's what you're looking for.

FORMULA: P=hρg

Answer:

Explanation:

Isomers are compounds with the same molecular formula but chemically distinctive structures. Compounds that vary in connectivity, or how the component atoms are related to one another, are known as constitutional isomers. They have distinct functional groups and bonding patterns according to the sequence in which the atoms are linked together.

From the information given:

The compound given is C₃H₆Br₂ and the constitutional isomer of the compound can be seen in the image attached below.

The formal charges are calculated as follows:

Formal charge = valence electron - 1/2(bonding electron) - lone electron

For Br:

Formal charge = 7 - 1/2(2) - 6

Formal charge = 7 - 1 - 6 = 0

For C:

Formal charge = 4 - 1/2(8) - 0

Formal charge = 4 - 4 = 0

For H:

Formal charge = 1 - 1/2(2)

Formal charge = 1 - 1 = 0

Answer:

See explanation

Explanation:

If we look at the structure of X, we will discover that X is an organic compound. The compound will certainly have a much lower melting point than sand.

This is because, sand is composed of high melting point inorganic materials.

Hence, even though the researcher accidentally spilled some sand into the the beaker containing the crystalline substance X, he does not need to be perturbed since the melting point of X is much lower than that of sand

Explanation:

A kind of chemical reaction in which a reaction between any combustible substance and an oxidizer takes place in order to form an oxidized product.

Eg: Fuel + O2 → CO2 + H2O.

The burning of charcoal is a combustion reaction.

A synthesis reaction occurs when two or more reactants combine to form a single product.

Eg: Na + Cl → NaCl

An example of a synthesis reaction is the combination of sodium (Na) and chlorine (Cl) to produce sodium chloride (NaCl).

A decomposition reaction occurs when one reactant breaks down into two or more products.

Eg: NaCl → Na + Cl

An example of a decomposition reaction is the breakdown of Sodium chloride to give sodium and chloride.

A single replacement reaction, sometimes called a single displacement reaction, is a reaction in which one element is substituted for another element in a compound.

Eg: Zn + 2 HCl → 2 ZnCl + H2

The reaction between zinc metal and hydrochloric acid to produce zinc chloride and hydrogen gas is an example of a single-displacement reaction.

A double replacement reaction is a type of chemical reaction that occurs when two reactants exchange cations or anions to yield two new products.

Eg: AgNO 3 + NaCl → AgCl + NaNO

The reaction between silver nitrate and sodium chloride to produce silver chloride and sodium nitrate is an example of a double-displacement reaction.

Answer:

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Answer:

3.1621 × 10²⁵ molecules

Explanation:

From the given information:

Moles of C2H8 = 52.5 moles

number of moles = mass/molar mass

molar mass of C2H8 = (6 *2) + (1*8)

= 12 + 8

= 20 g/mol

∴

52.5 moles = mass of C2H8 / 20 g/mol

mass of C2H8 = 52.5 moles × 20 g/mol

mass of C2H8 = 1050 grams

Recall that;

1 mole = 6.023 × 10²³ molecules

∴ 52.5 moles of C2H8 = (52.5 × 6.023 × 10²³) molecules

=3.1621 × 10²⁵ molecules

Answer:

Explanation:

The pH of a solution can be found by using the formula

[tex]pH = - log [ { H_3O}^{+}][/tex]

From the question we have

[tex]ph = - log(5.2 \times {10}^{ - 8} ) \\ = 7.28399[/tex]

We have the final answer as

Hope this helps you

The amount of energy needed to freeze 12.5 grams of water into ice is equals to 14.295 kilo joules.

Energy required to freeze water will be calculated by using the following equation as:

Q = mcT, where

m = mass of water = 12.5g = 0.0125kg

c = specific heat of water = 4.187 kJ/kg.K

T = temperature to freeze = 0 degree C = 273.15 K

On putting values we get,

Q = (0.0125)(4.187)(273.15)

Q = 14.295 kJ

Hence required amount of energy is 14.295 kJ.

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Answer:

gas molecules spread out in response to a concentration gradient.

Explanation:

Diffusion can be defined as the movement of gas molecules from a region of high concentration to a region of lower concentration until an equilibrium is attained or reached. This mixing of gas molecules in the liquid or gaseous state is due to their kinetic energy of random motion i.e without requiring bulk motion.

This ultimately implies that, diffusion is a phenomenon through which gas molecules in either a gaseous or liquid state spread out in response to a concentration gradient, which is simply the difference in concentration of the gases across a space.

In conclusion, increasing the surface area of a gas increases its collision rate and it's considered to be an evolutionary strategy that maximizes the diffusion of gas molecules by catalysing the rate of a gaseous reaction.

Answer:

6.56x10⁻³ mol

Explanation:

First we calculate how many HCl moles are there in 50.0 mL of a 0.1800 M solution:

Then we need to calculate how many HCl moles were in excess, that number is the same as the number of NaOH moles they reacted with:

Finally we calculate the difference between the original number of HCl moles and the number remaining after the reaction with XnCO₃:

Answer:

See explanation and image attached

Explanation:

When 1 mole of hydrogen is added to 3-hexyne, the addition occurs on the same face or side of the triple bond to yield cis-2-hexene in the presence of lindlar catalyst which prevents further hydrogenation. This is known as syn addition.

The syn addition is achieved because the hydrogen molecule is first adsorbed on the surface of the palladium metal and is subsequently attached to the same face of the triple bond in 3-hexyne as shown in the image attached to this answer.

Answer:

Option A. Substitution

Explanation:

To know which option is correct, let us define each option. This is illustrated below:

A substitution reaction is a reaction in which an halogen replaces hydrogen in a hydrocarbon to produce alkyl halide and the corresponding acid. For example:

RH + X₂ –> RX + HX

NOTE:

R => is an alkyl group

X => is an halogen (F₂, Cl₂, Br₂ or I₂)

Addition reaction is a reaction in which two reactants combined to form a new compound without any loss of the reactants. This reaction is peculiar to only unsaturated hydrocarbon. For example:

CₓHᵧ + A₂ —> ACₓHᵧA

NOTE:

CₓHᵧ => unsaturated hydrocarbon (alkene, alkyne)

A₂ => halogen (F₂, Cl₂, Br₂ or I₂) or HBr, HCl etc

Esterification is a reaction involving carbonxylic and alcohol to produce ester and water. For example:

RCOOH + HOR —> RCOOR + H₂O

NOTE:

R => is an alkyl group

Polymerization is a process of reacting smaller molecules called monomers to form a larger molecule called polymer.

With the information provided above, we can see that the reaction:

CH₄ + Br₂ —> CH₃Br + HBr

Is a substitution reaction since Br replaces H in CH₄ to produce CH₃Br and the corresponding acid i.e HBr

Answer:

[tex]2.17gO_2[/tex]

Explanation:

Hello there!

In this case, according to the given information, it turns out possible for us to calculate the mass of 4.09 x 10^22 molecules of oxygen gas by firstly keeping in mind that that 1 mole of it has a mass of 32.0 g and secondly that 1 mole of any substance contains 6.022x10^23 representative units, in this case, molecules of O2, and thus, the appropriate setup to perform this conversion is shown below:

[tex]4.09x10^{22}molecules \ O_2*\frac{1molO_2}{6.022x10^{23}molecules \ O_2}*\frac{32.0gO_2}{1molO_2} \\\\2.17gO_2[/tex]

Regards!

Answer:

I think it's 2-methylhept-2-ene

Explanation:

Hope this will help and correct me if I'm wrong.

Answer:

Angle of incidence = angle of reflection = 0

Explanation:

Given that,

A light beam strikes a shiny object at a 90-degree angle.

The angle made by incident ray and normal to the mirror is called the angle of incidence and the angle made by the reflected ray and the normal is called the angle of reflection.

Here, the beam strikes normally. So, the angle of incidence is 0.

A/c to the law of reflection,

Angle of incidence = angle of reflection

So, the angle of reflection is also equal to 0.

Answer: Its A nucleic acids

Explanation:

Nucleic acids, and DNA in particular, are key macromolecules for the continuity of life. DNA bears the hereditary information that's passed on from parents to children, providing instructions for how (and when) to make the many proteins needed to build and maintain functioning cells, tissues, and organisms.

Nucleic acids carry genetic information from parents to their children.

Nucleic acids are biopolymers, macromolecules, essential to all known forms of life.[1] They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main classes of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). If the sugar is ribose, the polymer is RNA; if the sugar is the ribose derivative deoxyribose, the polymer is DNA.

Nucleic acids are naturally occurring chemical compounds that serve as the primary information-carrying molecules in cells and make up the genetic material. Nucleic acids are found in abundance in all living things, where they create, encode, and then store information of every living cell of every life-form on Earth. In turn, they function to transmit and express that information inside and outside the cell nucleus to the interior operations of the cell and ultimately to the next generation of each living organism. The encoded information is contained and conveyed via the nucleic acid sequence, which provides the 'ladder-step' ordering of nucleotides within the molecules of RNA and DNA. They play an especially important role in directing protein synthesis.

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Answer:

HCl(aq) + KOH(aq)---------->KCl (aq)+ H2O(l)

Answer:

A rabbits respiration should be 30-60 breaths per minute

Answer:

0.877 M

Explanation:

Number of moles of ammonia = 0.879 g /17 g/mol = 0.05 moles

The reaction equation is ;

2NH3 + OBr-→ N2H4 + Br- + H2O

2 moles of NH3 reacts with 1 mole of hypobromite

0.05 moles of NH3 reacts with 0.05 moles ×1 mole/2 moles

= 0.025 moles

Number of moles = concentration × volume

Concentration = Number of moles / volume

Concentration = 0.025 moles × 1000/28.5

Concentration = 0.877 M