Q: Which of the following is the correct formula for calculating activation energy ($$E_a) $$from an energy diagram?

$$E_a = E_{\text{transition state}} - E_{\text{reactants}}$$

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 reacts with O2 to produce CO2 and H2O

Question 4

What is the oxidation number of oxygen in the compound NaO2?

Accepted Answer

$$-1$$

Question 5

Which of the following compounds would NOT be associated with the term 'formula unit'?

Accepted Answer

C2H6

Question 6

How many molecules are in 2.00 moles of water ($$H_2O$$)?

Accepted Answer

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

Question 7

A reaction has an activation energy ($$E_a) of 80 kJ. $$Another reaction has $$E_a = 143 kJ. $$Which reaction will proceed faster under the same conditions?

Accepted Answer

The reaction with $$E_a = 80 kJ$$

Question 8

Which of the following processes is an example of an endothermic reaction?

Accepted Answer

Water boiling

Question 9

Calculate the molar mass of nickel(II) chloride hexahydrate, $$NiCl_2$$ \cdot 6H_2O$$.

Accepted Answer

$$237.69 g/$$mol

Question 10

Which element is being reduced in the following reaction?

$$Cr_2O_7$$^{2-}$$ + 3 $$HNO_2$$ + 5 H^+ \rightarrow 2 Cr$$^{3+}$$ + 3 NO_3$^- + 4 H_2O$$

Accepted Answer

Chromium

Question 11

Which of the following statements about exothermic reactions is TRUE?

Accepted Answer

They release heat to the surroundings

Question 12

If 12.3 g of $$H_2$$ reacts with excess $$O_2$$ according to $$2 H_2$ (g) + O_2$ (g) \rightarrow 2 H_2O (g)$$, 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 13

Which of the following will increase the rate of a chemical reaction?

Accepted Answer

Increasing the concentration of reactants

Question 14

What is the energy value for the products in the following energy diagram if the y-axis is labeled in kJ and the product line is at 100 kJ?

Accepted Answer

$$100$$ 	ext{ kJ}$

Question 15

Which of the following is the correct formula for calculating activation energy ($$E_a) $$from an energy diagram?

Accepted Answer

$$E_a = E_{	ext{transition state}} - E_{	ext{reactants}}$$

Question 16

Which of the following reactions is a redox reaction?

Accepted Answer

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

Question 17

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

Accepted Answer

It lowers the activation energy

Question 18

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

Accepted Answer

The products are lower in energy than the reactants

Question 19

If the density of ethanol ($$CH_3CH_2OH) is$$ $$0.789 g/mL$$, how many milliliters are needed to produce $$4.8 g of$$ $$H_2O in $$the reaction $$CH_3CH_2OH (l) + 3 O_2$ (g) \rightarrow 3 H_2O (l) + 2 CO_2$ (g)$$? (Molar mass $$CH_3CH_2OH = 46.07 g/$$mol, $$H_2O = 18.02 g/$$mol)

Accepted Answer

$$2.18$$ 	ext{ mL}$

Chemical Quantities and Reactions: Foundations for Organic Chemistry

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