Energy in Chemical Reactions - Test Test

Question 1

Which direction does thermal energy flow in this diagram?

Revolt · Accepted Answer

A: Heat flows from the hand to the ice cream.

Question 2

What is the overall enthalpy change triangle cap h sub rxn for the system?

Revolt · Accepted Answer

A: 300 kJ

Question 3

Which label shows the overall enthalpy change and is the reaction exothermic or endothermic?

Revolt · Accepted Answer

D: D, endothermic.

Question 4

Consider these intermediate chemical equations. cap c times s plus 1 half cap o sub 2 g rightarrow CO times g CO times g plus 1 half cap o sub 2 g rightarrow CO sub 2 times g How will oxygen appear in the final chemical equation?

Revolt · Accepted Answer

D: cap o sub 2 times g  as a reactant

Question 5

A welding torch produces a flame by burning acetylene fuel in the presence of oxygen. This flame is used to melt a metal. Which energy transformation represents this process?

Revolt · Accepted Answer

C: chemical energy into thermal energy

Question 6

Which best describes heat?

Revolt · Accepted Answer

B: energy that flows from a hot mug of tea to a cold hand; C: energy that decreases as a car slows to a stop

Question 7

cap h sub 2 cap o has a triangle cap h sub vap is equal to 40 point 7 kJ over mol What is the quantity of heat that is released when 27 point 9 g of cap h sub 2 cap o condenses? Use q is equal to n triangle cap h

Revolt · Accepted Answer

A: 60 point 0 0 kJ

Question 8

Nitrogen dioxide, NO sub 2 times g Δ⁢H_f=33.84kJ/mol , is decomposed according to the reaction: 2 NO sub 2 g rightarrow cap n sub 2 times g plus 2 cap o sub 2 g What is the enthalpy change when 2 point 5 0 mol of nitrogen dioxide decomposes? Use Δ⁢H_rxn=∑(Δ⁢H_f_1p⁢r⁢o⁢d⁢u⁢c⁢t⁢s)−∑(Δ⁢H_f_1r⁢e⁢a⁢c⁢tan⁡t⁢s)

Revolt · Accepted Answer

C: 84 point 6 kJ  of energy released

Question 9

Which statement about enthalpy is true?

Revolt · Accepted Answer

C: Enthalpy is a state function because its change depends only on initial and final conditions.

Question 10

Consider these intermediate chemical equations. cap c times s plus cap o sub 2 times g rightarrow CO sub 2 times g triangle cap h sub 1 is equal to negative 393 point 5 kJ 2 CO g plus cap o sub 2 times g rightarrow 2 CO sub 2 g triangle cap h sub 2 is equal to negative 566 point 0 kJ 2 cap h sub 2 cap o g rightarrow 2 cap h sub 2 g plus cap o sub 2 times g triangle cap h sub 3 is equal to 483 point 6 kJ The overall chemical equation is C(s)+H_2​O(g)→CO(g)+H_2​(g) To calculate the final enthalpy of the overall chemical equation, which step must occur?

Revolt · Accepted Answer

D: Reverse the second equation, and change the sign of the enthalpy. Then, add.

Energy in Chemical Reactions - Test Test Answers

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