CHEMISTRY HIGH SCHOOL

Which substance is an example of an element?A) bronze
B) copper
C) methane
D) rust

Answers

Answer 1
Answer: Copper is an element. An element is a substance that is entirely made from one type of atom.
Answer 2
Answer:

It is B. I took the test!!

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How much energy is passed to the next trophic level in the food chain?

Answers

Answer:

10%

Explanation:

Out of the original layer, only ten percent is transferred to the next

Consider the following reversible, exothermic chemical reaction: 2C2H2(g) + 5O2(g) ↔4CO2(g) + 2H2O(g) All BUT one of the conditions will cause equilibrium to shift right and produce more of the products. Which change will cause the reaction to shift to the left?
A) adding oxygen
B) adding CO2
C) increasing the pressure
D) decreasing the temperature

Answers

Answer : The correct option is, (B) adding CO_2

Explanation :

Le-Chatelier's principle : This principle states that if any change in the variables of the reaction, the equilibrium will shift in the direction to minimize the effect.

Option A : adding oxygen

If the concentration of O_2 is increased on reactant side then the equilibrium will shift in the direction where decrease of concentration of O_2 takes place. Therefore, the equilibrium will shift in the right direction.

Option B : adding CO_2

If the concentration of CO_2 is increased on product side then the equilibrium will shift in the direction where decrease of concentration of CO_2 takes place. Therefore, the equilibrium will shift in the left direction.

Option C : increasing the pressure

If the pressure of the container is increased then the equilibrium will shift in the direction where the less number of moles of gas molecules is taking place. As the number of moles of gas molecules is greater at the product reactant side and less at product side. So, the equilibrium will shift in the right direction.

Option D : decreasing the temperature

As the given reaction is an exothermic reaction in which the heat is released during a chemical reaction. That means the temperature is decreased on the reactant side. If the temperature is decreased in the equilibrium then the equilibrium will shift in the direction where, temperature is getting increased. Thus, the reaction will shift to the right direction i.e, towards the product.
Adding CO2 increases Q and makes Q > K (K being the equilibrium constant for this reaction).  As a result, the reaction will favor reactants until Q=K, so adding CO2 causes the reaction to proceed to the left.  B is the correct answer.

Which chemical equation represents the reaction of an Arrhenius acid and an Arrhenius base?(1) HC2H3O2(aq) + NaOH(aq) --> NaC2H3O2(aq) + H2O(l)
(2) C3H8(g) + 5 O2(g)--> 3 CO2(g) + 4 H2O(l)
(3) Zn(s) + 2 HCl(aq)--> ZnCl2(aq) + H2(g)
(4) BaCl2(aq) + Na2SO4(aq) --> BaSO4(s) + 2 NaCl(aq)

Answers

Answer : The correct option is, (1)

Explanation :

According to the Arrhenius acid-base concept,

Arrhenius acid is a species that produces H^+ ion in an aqueous solution and Arrhenius base is a species that produces OH^- ion in an aqueous solution.

From the given options, option 1 chemical equation represents the reaction of an Arrhenius acid and an Arrhenius base. In this reaction, HC_2H_3O_2 produces H^+ ion in an aqueous solution and act as an Arrhenius acid, NaOH produces OH^- ion in an aqueous solution and act as an Arrhenius base.

While the other options does not represents the reaction of an Arrhenius acid and an Arrhenius base.

Reaction 2 is an example of combustion reaction.

Reaction 3 is an example of single-displacement reaction.

Reaction 4 is an example of double-displacement reaction.

Hence, the correct option is, (1)
The chemical equation that represents the reaction of an Arrhenius acid and an Arrhenius base is 1) HC2H3O2 (aq) + NaOH (aq) ---> NaC2H3O2 (aq) + H2O (I) 

Atoms A and X are fictional atoms. Suppose that the standard potential for the reduction of X^2+ is +0.51 V, and the standard potential for the reduction of A^2+ is -0.33. Find the standard potential for an electrochemical cell with the cell reaction that follows.

Answers

While the reaction is not shown, based on those atoms and reduction potentials, the only reasonable favorable equation we can form is:

A(2+) + X -> A + X(2+)

The standard reduction potential for the cell is the cathode's reduction potential minus the anode's reduction potential, or 0.51-(-0.33)=0.84.

15 The electronegativity difference between the atoms in a molecule of HCl can be used to determine(1) the entropy of the atoms(2) the atomic number of the atoms
(3) the first ionization energy of the atoms
(4) the polarity of the bond between the two atoms

Answers

Answer : The correct option is, (4)

Explanation :

  • Electronegativity : It is a chemical property which measures the ability of an atom to attract an electrons towards itself.
  • Electronegativity difference : The difference in the electronegativity of the two atoms determines their polarity.

If the electronegativity difference between the two atoms is zero then the molecule is non-polar.

If the electronegativity difference between the two atoms is non-zero then the molecule is polar.

Therefore, the electronegativity difference between the atoms in a molecule of HCl can be used to determine the polarity of the bond between the two atoms


(4) the polarity of the bond between the two atoms

The more important the difference in electronegativity is, the more polarized the bond is.

The _______ receives digested food components and stores the glucose to be released into the blood stream for future use.A. liver
B. stomach
C. small intestine
D. large intestine

Answers

its actualy liver! i got small intestine wrong:/
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