Gustaf observes a chemical reaction between two substances in a glass beaker. while observing the reaction, he touches the beaker and notices that it feels warm. why does the beaker feel warm? a. the beaker absorbed energy that was released by the chemical reaction. b. the beaker released energy that was absorbed by gustaf's hand. c. the beaker absorbed energy that was released from gustaf's hand. d. the beaker released energy that was absorbed by the chemical reaction.

a. The beaker absorbed energy that was released by the chemical reaction.  

Explanation:

Gustaf was watching an exothermic reaction, so the beaker got hot.

Exothermic reaction is one in which there is release of energy. In this process, energy production persists only through continuous supply of energy.

Gustaf was watching an exothermic reaction between two substances in a glass beaker. This reaction occurs with the release of energy because it is an exothermic reaction. In this way, the glass absorbed energy that was released by the chemical reaction.

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol