Q: Which of the following reactions is endothermic?

$$N_2(g$$) + $$O_2(g) + 43$$ \text{ kJ} \rightarrow 2NO(g)$$

Question 1

Which of the following best describes the activation energy ($$E_a) in a $$chemical reaction?

Accepted Answer

It is the minimum energy required for reactant molecules to collide and form products.

Question 2

Consider the reaction: $$2H_2(g) + O_2$(g) \rightarrow 2H_2O(g). $$Which law is demonstrated by the fact that the number of hydrogen and oxygen atoms is the same on both sides of the equation?

Accepted Answer

Law of Conservation of Mass

Question 3

Which of the following reactions is an example of a decomposition reaction?

Accepted Answer

$$2KClO_3(s) \rightarrow 2KCl(s) + 3O_2(g)$$

Question 4

In an exothermic reaction, which of the following statements is TRUE?

Accepted Answer

Heat is released and the products have lower energy than the reactants.

Question 5

Balance the following chemical equation: $$Fe_2O_3(s) + H_2$(g) \rightarrow Fe(s) + H_2O(g). $$What are the correct coefficients?

Accepted Answer

$$1, 3, 2, 3$$

Question 6

Which of the following is a double replacement reaction?

Accepted Answer

$$AgNO_3(aq) + $$NaCl(aq) \rightarrow AgCl(s) + $$NaNO_3(aq$$)$$

Question 7

A chemical reaction is classified as a combustion reaction if:

Accepted Answer

It involves a substance reacting rapidly with oxygen to produce heat and light.

Question 8

Which of the following best describes an oxidation-reduction (redox) reaction?

Accepted Answer

A reaction involving the transfer of electrons from one substance to another.

Question 9

Given the reaction $$Zn(s) + 2HCl(aq) \rightarrow $$ZnCl_2$$(aq) + H_2$(g)$$, which substance is oxidized?

Accepted Answer

$$Zn$$

Question 10

Which of the following is NOT a guideline for balancing chemical equations?

Accepted Answer

Change the chemical formulas of reactants to balance the equation.

Question 11

Which reaction type is represented by $$2Al(s) + 3CuSO_4(aq) \rightarrow Al_2$(SO_4$)_3(aq) + 3Cu(s)$$?

Accepted Answer

Single replacement

Question 12

In the reaction $$N_2(g) + 3H_2(g$$) \rightarrow 2NH_3(g)$$, how many total atoms are present on each side of the equation?

Accepted Answer

8 atoms

Question 13

Which of the following statements about the Law of Constant Composition is correct?

Accepted Answer

A chemical compound always contains the same proportion of elements by mass.

Question 14

Which of the following reactions is endothermic?

Accepted Answer

$$N_2(g$$) + $$O_2(g) + 43$$ 	ext{ kJ} ightarrow 2NO(g)$$

Question 15

If a reaction has an activation energy of $$60 	ext{ kJ}$$ and a heat of reaction of $$-250 	ext{ kJ}$$, what type of reaction is it?

Accepted Answer

Exothermic

Question 16

Which of the following is the correct balanced equation for the combustion of methane ($$CH_4$$)?

Accepted Answer

$$CH_4(g) + 2O_2(g$$) \rightarrow $$CO_2(g) + 2H_2O(g$$)$$

Question 17

In the reaction $$2K(s) + 2H_2O(l) \rightarrow 2KOH(aq) + H_2$(g)$$, which element is reduced?

Accepted Answer

Hydrogen ($$H)$$

Question 18

Which of the following is a correct statement about single replacement reactions?

Accepted Answer

One element replaces another element in a compound.

Question 19

Which of the following is the correct set of coefficients to balance the equation: $$Mg_3$$($$PO_4)_2$$ + $$MgCl_2$$ \rightarrow $$Mg_2$$($$PO_4)_2$$ + $$MgCl_2$$?

Accepted Answer

$$2, 3, 1, 6$$

Chemical Reactions and Equations: Energy, Balancing, and Types

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