Question 1

Which of the following is NOT an observable evidence of a chemical reaction?

Accepted Answer

Change in mass

Question 2

When balancing a chemical equation, what must be equal on both sides of the equation?

Accepted Answer

The number and type of atoms

Question 3

Which of the following best describes a combustion reaction?

Accepted Answer

A compound containing C and H (or C, H, and O) reacts with $$O_2 to $$produce $$CO_2$$ and $$H_2O$$

Question 4

What is the oxidation number of oxygen in $$H_2O_2 ($$hydrogen peroxide)?

Accepted Answer

$$-1$$

Question 5

Which of the following compounds contains an element with an oxidation number of zero?

Accepted Answer

$$Cl_2$$

Question 6

In the reaction $$2Li (s) + Zn$$^{2+}$$ (aq) \rightarrow 2Li$$^{+}$$ (aq) + Zn (s)$$, which element is oxidized?

Accepted Answer

Lithium

Question 7

Calculate the molar mass of $$NiCl_2$$ \cdot 6H_2O$$ (nickel(II) chloride hexahydrate). (Atomic masses: Ni = 58.69, Cl = 35.45, H = 1.008, O = 16.00)

Accepted Answer

$$237.69\ g/mol$$

Question 8

How many molecules are in 2.00 moles of $$H_2O$$?

Accepted Answer

$$1.204 	imes 10$$^{24}$$

Question 9

If 12.3 g of $$H_2$$ reacts with excess $$O_2$$ according to $$2H_2 (g) + O_2$ (g) \rightarrow 2H_2O (g)$$, how many grams of $$H_2O$$ are produced? (Molar mass $$H_2 = 2.02$$\ g/mol$$, H_2O = 18.02$$\ g/mol$$)

Accepted Answer

$$54.9\ g$$

Question 10

Which of the following processes is endothermic?

Accepted Answer

Water boiling

Question 11

Which factor does NOT increase the rate of a chemical reaction?

Accepted Answer

Decreasing the temperature

Question 12

What is the activation energy ($$E_a) $$for a reaction if the energy of the reactants is $$50\ kJ$$ and the transition state is $$200\ kJ$$?

Accepted Answer

$$150\ kJ$$

Question 13

Which of the following statements about exothermic reactions is TRUE?

Accepted Answer

The reaction feels warm to the touch

Question 14

A reaction has an activation energy of $$215\ kJ. $$Which of the following reactions will occur the fastest?

Accepted Answer

A reaction with $$E_a = 80\ kJ$$

Question 15

Which of the following is a double displacement reaction?

Accepted Answer

$$Ba(NO_3$)_2 (aq) + Na_2SO_4 (aq) \rightarrow $$BaSO_4$$ (s) + 2NaNO_3 (aq)$$

Question 16

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

It decreases the activation energy

Question 17

Which of the following reactions is a redox reaction?

Accepted Answer

$$2AgNO_3 (aq) + Cu (s) \rightarrow Cu(NO_3$)_2 (aq) + 2Ag (s)$$

Question 18

If you have 73.1 kg of $$NaCl$$, how many formula units are present? (Molar mass $$NaCl = 58.44\ g/mol$$, $$1\ mol = 6.022 	imes 10$$^{23}$$ formula units)

Accepted Answer

$$7.54 	imes 10$$^{26}$$

Question 19

Which of the following is true regarding the energy diagram for an exothermic reaction?

Accepted Answer

The products are at a lower energy than the reactants

Chemical Quantities and Reactions – GOB Chemistry Study Notes

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