Chemical Energy Changes

In a test tube a powder is added to water. The result is observed that the temperature increased. Therefore

• The rxn is endothermic and the enthalpy is positive.

• The rxn is endothermic and the enthalpy is negative.

• The rxn is exothermic and the enthalpy is positive.

• The rxn is exothermic and the enthalpy is negative.

Tags

NGSS.HS-PS1-4

• Endothermic

• Exothermic

• Isothermic

Tags

NGSS.HS-PS1-4

• Endothermic

• Exothermic

• Isothermic

Tags

NGSS.HS-PS1-4

*A piece of metal has a mass of 43.2 grams and changes from a temperature of 45.2 C to 87.2 C. If the metal has a specific heat of 0.388 J/g C, how much heat energy was gained?

• 2.59 J

• 43.0 kJ

• 704 J

• 1020 J

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

*A hot rock is placed in a bucket of water and the temperature of the system becomes 35.5 C. If the rock was 1226 g and 54.6 C initially and the water was 2455 grams and 23.4 C. What is the specific heat of the rock?

• 1.24 J/g C

• 5.30 J/g C

• 7.00 J/g C

• 0.123 J/g C

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

Which equation would you use to solve the following: Calculate the heat necessary to change 10 g of ice(s) at 0°C to 10 g of water(l) at 0°C.

• q=mCΔT

• q= H_v*m

• q= H_f*m

• PV=nRT

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

*Determine the amount of heat energy required to convert 10 grams of ice at -20 °C to steam at 125 °C.

• 31012 J

• 30292 J

• 33938 J

• 32293 J

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

*What is the specific hear of an alloy if 4210 joules are required to raise the temperature of a 30. g sample by 180.°C?

• 0.78 J/g°C

• 0.25 J/g°C

• 1.78 J/g°C

• 2.34 J/g°C

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-2

*How much heat is needed to raise the temperature of 50.0 g of iron by 15.0°C? (specific heat of iron = 0.444 J/g°C)

• 333 J

• 33.3 J

• 33300 J

• 3330 J

Tags

NGSS.HS-PS3-1

*An alloy has a specific heat of 1.25 cal/g°C and is at 25 °C. When it is dropped into warm water, the alloy absorbs 750 cal of heat. If the final temperature of the alloy is 75 °C, what is its mass?

• 12 g

• 2.4 g

• 24 g

• 36 g

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4