CHEMISTRY HIGH SCHOOL

A chemical reaction in which two or more substances undergo a chemical union to form a more complex substance is a _______ reaction. A. double replacement
B. substitution
C. decomposition
D. combination

Answers

Answer 1
Answer:

A chemical reaction in which two or more substances undergo a chemical union to form a more complex substance is a combination reaction.

What is a chemical reaction?

Chemical reactions are defined as reactions which occur when a substance combines with another substance to form a new substance.Alternatively, when a substance breaks down or decomposes to give new substances it is also considered to be a chemical reaction.

There are several characteristics of chemical reactions like change in color, change in state , change in odor and change in composition . During chemical reaction there is also formation of precipitate an insoluble mass of substance or even evolution of gases.

There are three types of chemical reactions:

1) inorganic reactions

2)organic reactions

3) biochemical reactions

During chemical reactions atoms are rearranged and changes are accompanied by an energy change as new substances are formed.

Learn more about chemical reactions,here:

brainly.com/question/29762834

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Answer 2
Answer:

Answer : The correct option is, (D) Combination

Explanation :

  • Double replacement reaction : A chemical reaction in which a positive cation and a negative anion of the two reactants exchange places to give two new products or compounds.

        The general representation of this reaction is,

         AB+CD\rightarrow AD+CB

         (A and C are the cations, B and D are the anions)

  • Substitution reaction : A chemical reaction in which a more reactive element displaces the least reactive element.

        The general representation of this reaction is,

         A+BC\rightarrow A+CB

  • Decomposition reaction : A chemical reaction in which a bigger compound breaks into two or more smaller compounds or elements.

        The general representation of this reaction is,

         AB\rightarrow A+B

  • Combination reaction : A chemical reaction in which two or more substances react to form a more complex substance.

        The general representation of this reaction is,

         A+B\rightarrow AB

Hence, the correct option is, (D) Combination

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Calculate the percent ionization of nitrous acid in a solution that is 0.311 M in nitrous acid (HNO2) and 0.189 M in potassium nitrite (KNO2). The acid dissociation constant of nitrous acid is 4.5 × 10^-4. Calculate the percent ionization of nitrous acid in a solution that is 0.311 M in nitrous acid (HNO2) and 0.189 M in potassium nitrite (KNO2). The acid dissociation constant of nitrous acid is
4.5 × 10^-4.

Answers

HNO2 =====> H+ + NO2-
Initial concentration = 0.311
C = -x,x,x 
E = 0.311-x,x,x

KNO2 ====>K+ + NO2- 
Initial concentration = 0.189 
C= -0.189,0.189,0.189 
E = 0,0.189,0.189
 

What volume measured in stp will 3.75 grams of helium gas occupy?

Answers

Molar mass  helium gas :

He = 4.0 g/mol

number of moles:  3.75 / 4.0 => 0.9375 moles

1 mole ------ 22.4 ( at STP)
0.9375 ------ ?

volume = 0.9375 x 22.4 / 1

Volume = 21 / 1

Volume = 21 L

hope this helps!

Sodium chloride, NaCl forms in this reaction between sodium and chlorine. 2Na(s) + Cl2(g) → 2NaCl(s) How many moles of NaCl result from the complete reaction of 3.9 mol of Cl2? Assume that there is more than enough Na.

Answers

Answer: 7.8 moles of NaCl result from the complete reaction of 3.9 mol of Cl_2

Explanation:

To calculate the moles :

\text{Moles of solute}=\frac{\text{given mass}}*{\text{Molar Mass}}    

\text{Moles of} Cl_2=3.9mol

2Na(s)+Cl_2(g)\rightarrow 2NaCl(s)

As Na is the excess reagent, Cl_2 is the limiting reagent as it limits the formation of product.

According to stoichiometry :

1 mole of Cl_2 gives = 2 moles of NaCl

Thus 3.9 moles of Cl_2 will give=\frac{2}1}* 3.9=7.8moles  of NaCl

7.8 moles of NaCl result from the complete reaction of 3.9 mol of Cl_2

Which law states that the volume of a gas is proportional to the moles of the gas when pressure and temperature are kept constant?

Answers

I believe this would be Avogadro's law which states ''Equal volumes of all gases, at the same temperature and pressure, have the same number of molecules regardless of their chemical nature and physical properties.''

Answer:

boyles law

Explanation:

How many moles of hydrogen are needed to produce 13.78 mol of ethane?

Answers

This is an incomplete question, here is a complete question.

The following balanced equation shows the formation of ethane (C₂H₆).

C_2H_2+2H_2\rightarrow C_2H_6

How many moles of hydrogen are needed to produce 13.78 mol of ethane?

1) 3.445 mol

2) 6.890 mol

3) 27.56 mol

4) 55.12 mol

Answer : The number of moles of hydrogen needed are, (3) 27.56 mol

Explanation : Given,

Moles of ethane = 13.78 mol

The given balanced chemical reaction is:

C_2H_2+2H_2\rightarrow C_2H_6

From the balanced chemical reaction we conclude that,

As, 1 mole of ethane produced from 2 moles of hydrogen

So, 13.78 mole of ethane produced from 13.78* 2=27.56 moles of hydrogen

Thus, the number of moles of hydrogen needed are, 27.56 mol
Ethane is an alkane. Methane is also an alkane and is considered to be the simplest alkane. The difference is ethane has only 2 carbon. That carbon has 6 hydrogen attached to it. So what we do is we multiply the moles of ethane by the number of hydrogen (by dimension analysis) resulting to 82.68 moles H.

Which statement best applies collision theory to preventing a dangerous reaction from occurring? Store the reactants together at a low pressure. Keep all sparks or flames away from the reactants. Store the reactants together at a low temperature. Keep the reactants in separate containers.

Answers

Answer:


According to collision theory, to preventing a dangerous reaction from occurring, the best is to keep reactants in separate containers (last statement).


Justification:


Collison theory states that the the reactant substances (atoms, ions or molecules) must first collide to react and form the products.

Additionally, to form the products, the collisions must meet two requirements:

  • the reactant substances must collide with the correct orientation, and
  • the reactant substances must collide with energy enough to form the activated complex (transition state).

Hence, the collision theory permits youpreventing a dangerous reaction from occurring, by using the elemental knowledge that the substances must first collide in order to they react, and so the most effective way is to keep the reactants in separate contaners, preventing the reactants from coming into direct contact.

Answer: Option (d) is the correct answer.

Explanation:

According to collision theory, the particles should colloid frequently and they should be placed in proper orientation.

Whereas sometimes even at low temperature, reactant particles have enough energy. As a result, they tend to colloid or react with each other. Hence, it leads to a chemical reaction which might be dangerous.

Therefore, it is suitable to keep the reactant particles in separate containers so that a chemical reaction cannot take place.

So, we can conclude that the statement keep the reactants in separate containers best applies collision theory to preventing a dangerous reaction from occurring.
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