Enthalpy Changes

If you flip the equation, ΔH……

• Stays the same

• Is divided by 2

• Is multiplied by 2

• Flips too

What is a tool that measures the heat of chemical reactions?

• calorimeter

•  calorie

• Styrofoam™ cup

• none of these

which of the following enthalpy changes represent the enthalpy change of formation?

• Mg(s) + Cl₂(g) → MgCl₂(s)

• Mg²⁺(g) + 2 Cl ^-(g) → MgCl₂(aq)

• O2(g) → 2 O(g)

• 2Mg (s) + O₂(g) → 2MgO(S)

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Which statement describes characteristics of an endothermic reaction?

• The sign of △H is positive and the products have less potential energy then the reactants

• The sign of △H is negative, and the products have less potential energy than the reactants

• The sign of △H is positive and the products have more potential energy then the reactants

• The sign of △H is positive, and the products have more potential energy than the reactants

Tags

NGSS.HS-PS1-4

Which tendencies favor a spontaneous reaction?

• decreasing enthalpy and decreasing entropy

• increasing enthalpy and increasing entropy

• increasing enthalpy, and decreasing entropy

• decreasing enthalpy and increasing entropy

Which phrase best describe the following reaction 2H₂ + O₂ --> H₂O + energy?

• endothermic, absorbing energy

• endothermic, releasing energy

• exothermic, releasing energy

• exothermic, absorbing energy

Tags

NGSS.HS-PS1-4

A 0.20 kilogram sample of lead at 120⁰C is put in to a calorimeter containing 0.30 kg of water at 18⁰C. The equilibrium temperature of the mixture is 20.⁰C. Compared to the heat lost by the lead, the heat gained by the water is

• the same

• less

• more

Tags

NGSS.HS-PS3-4

The changes in ice to water involve

• and absorption of heat and an increase in entropy

• a release of heat and an increase in entropy

• a release of heat and a decrease in entropy

• an absorption of heat and a decrease in entropy

Based on the equation △G = △H - T△S, a chemical reaction will most likely occur spontaneously if

• △H is + and △S is +

• △H is - and △S is +

• △H is - and △S is -

• △H is + and △S is -

The heat of reaction (△H) is equal to the

• entropy of the reactants minus the entropy of the products

• entropy of the products minus the entropy of the reactants

• heat content of the reactants minus the heat content of the products

• heat content of the products minus the heat content of the reactants

Tags

NGSS.HS-PS3-1