# What is one environmental advantage of using fuel cells that are based on hydrogen rather than on hydrocarbons such as butane?

## What is one environmental advantage of using fuel cells that are based on hydrogen rather than on hydrocarbons such as butane?

Hydrogen fuel cells produce only water as a product, unlike fuel cells that use hydrocarbons, which release carbon dioxide. Carbon dioxide contributes to global warming via the enhanced atmospheric greenhouse effect.

## How many bonds are formed when two molecules of NF3 are produced according to the equation in the box above?

six
(b) How many bonds are formed when two molecules of NF3 are produced according to the equation in the box above? There are six N–F bonds formed.

What is enthalpy AP Chem?

The enthalpy of a reaction is the heat energy it contains. Enthalpy is represented by H in equations. The most important law when looking at enthalpy is Hess’s Law: the enthalpy change accompanying a chemical change is independent of the way in which the chemical change occurs.

### How do you find the enthalpy of a reaction?

Use the formula ∆H = m x s x ∆T to solve. Once you have m, the mass of your reactants, s, the specific heat of your product, and ∆T, the temperature change from your reaction, you are prepared to find the enthalpy of reaction. Simply plug your values into the formula ∆H = m x s x ∆T and multiply to solve.

### How do you find change in enthalpy?

To do the calculation, you would normally just work out the amount of heat evolved or absorbed in your particular reaction, and then scale it up to give an enthalpy change per mole. You will find examples of this in Chapter 5 of my chemistry calculations book.

Why do we prefer to use fuel cells rather than combustion engines?

Hydrogen fuel cells are cleaner and more efficient than traditional combustion-based engines and power plants. Hydrogen and fuel cells can also be used in mobile applications to power vehicles and mobile power packs. The benefits of fuel cells are: Reduced greenhouse gas emissions.

#### What is the bond enthalpy for the C S bond in kJ mol?

Common Bond Energies (D

Bond D (kJ/mol) r (pm)
C-S 272 182
C=S 573 160
C-F 485 135
C-Cl 327 177

#### Which of the following changes is not exothermic *?

Which of the following changes is not exothermic? Melting copper.

What is entropy AP chemistry?

Entropy is a thermodynamic function that describes the number of arrangements (positions and/or energy levels) that are available to a system existing in a given state. Entropy is closely related to probability.