# L USSAC ’ S L AW Lussac’s Law Old man Lussac determined the relationship between temperature and pressure of a gas. He measured the temperature of air.

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L USSAC ’ S L AW

Lussac’s Law Old man Lussac determined the relationship between temperature and pressure of a gas. He measured the temperature of air at different pressures, and observed a pattern of behavior which led to his mathematical law. During his experiments volume of the system and amount of gas were held constant. Old man Lussac determined the relationship between temperature and pressure of a gas. He measured the temperature of air at different pressures, and observed a pattern of behavior which led to his mathematical law. During his experiments volume of the system and amount of gas were held constant.

Pressure depends on Temp The higher the temperature of a gas, the higher the pressure that the gas exerts The reverse of that is true as well, a the temperature of a gas decreases – the pressure decreases. Think about the pressure of a set of tires on a car The higher the temperature of a gas, the higher the pressure that the gas exerts The reverse of that is true as well, a the temperature of a gas decreases – the pressure decreases. Think about the pressure of a set of tires on a car

Pressure Gauge Pressure Gauge Today’s temp: 35°F

Pressure Gauge Pressure Gauge Today’s temp: 85°F

The pressure increases when temperature increases because the molecules are moving with greater speed and colliding against the sides of their containers more often. Pressure

Temp Pressure How does Pressure and Temperature of gases relate graphically? P/T = k Volume, # of particles remain constant Volume, # of particles remain constant

Lussac’s Mathematical Law: What if we had a change in conditions? since P/T = k P 1 P 2 T 1 T 2 = Eg: A gas has a pressure of 3.0 atm at 127º C. What is its pressure at 227º C?

 T 1 = 127°C + 273 = 400K  P 1 = 3.0 atm  T 2 = 227°C + 273 = 500K  P 2 = ?  T 1 = 127°C + 273 = 400K  P 1 = 3.0 atm  T 2 = 227°C + 273 = 500K  P 2 = ? 1)determine which variables you have:

2) Plug in the variables: (500K)(3.0atm) = P 2 (400K) P 2 = 3.8atm 3.0atm P 2 400K 500K = = 3) Cross multiply and chug

LAW RELAT- IONSHIP Equation CON- STANT Boyle’s P VP VP VP V P 1 V 1 = P 2 V 2 T Charles’ V TV TV TV T V 1 /T 1 = V 2 /T 2 P Gay- Lussac’s P TP TP TP T P 1 /T 1 = P 2 /T 2 V

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