Which of the following involve endothermic reactions? (select all that apply)

A. A chemical cold pack

B. Gasoline in a car engine

C. Cooking rice

D. A candle flame

When a 6.50-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 21.6 degrees C to 37.8 degrees C. Calculate delta H (in kJ/mol NaOH) for the solution process.

Vanillin, a flavoring agent, is made up of carbon, hydrogen, and Oxygen atoms. When a sample of Vanillin weighing 2.500g burns in Oxygen, 5.79 g of carbon dioxide and 1.18 g of water are obtained. What is the empirical formula of Vanillin?

A 13.8 g sample of X reacts with a sample of Y to form 68.3 g of XY. What is the mass of Y that reacted

A neutron walks into a gas station to buy some snacks. He asks the cashier,"How much?" The cashier replies, "For you? No charge." what does this mean?

How many mL of a 0.250M sodium hydroxide solution is needed to neutralize 25.0 mL of a 0.430M sulfuric acid solution?

In natural convection heat transfer, the parameter is the Choose the right answer a) Nusselt number b) Rayleigh number c) Grashof number d) Lewis number

An insulator: A. Conducts heat well B. Does not conduct heat well C. Is used to heat cold objects D. Is used to cool hot objects

Which of the following choices would have a negative entropy change? A. N2 (g) + 3H2 (g) - >2NH3 (g) B. CaCO3 (s) - > CaO (s) + CO2 (g) C. H2O (s) - > H2O (l) D. Fe2O3 (s) + 3C (s) - > 2Fe (s) + 300 (g)

Increasing the temperature of a liquid-solid solution will:

What is the most abundant substance dissolved in sea water? magnesium chloride sodium chloride