An unknown substance undergoes a chemical change that gives off heat. What can you tell me about this substance?

An object has a mass of 6.8 g and a volume of 34 mL. What is the density of the object? 0.04 g/mL 0.1 g/mL 0.2 g/mL 5 g/mL

Is gold a compound or an element

How many neutrons are in an atom of Uranium-235?

The volume occupied by 9.03*10^23 molecules of N2 gas at STP is closest to? A) 1.50 L B).500 L C) 22.4 L D) 33.6 L

For the combustion reaction of C9H12 in O2: how many moles of O2 is required to react with 0.67 mol C9H12?

A 10 pound block of lead-210 has a half-life of 22 years. What percentage of the block still contains lead-210 after 60 years? 1.5% 15% 77% 27%

Combined gas law problem: a balloon is filled with 500.0 mL of helium at a temperature of 27 degrees Celsius and 755 mmHg. As the balloon rises in the atmosphere, the pressure and temperature drop.

1. What hypothesis could you propose about the relationship between the position of a type of atom in a molecule and the number of bonds that the atom forms? Explain your thinking.

The molality of a solution is a measure of - A - moles of solute per kilogram of solution B - moles of solute per liter of solution C - moles of solute per kilogram of solvent D - moles of solute per liter of solvent

Which technology has allowed for exploration beyond our solar system? A) space probe B) space station C) space shuttle D) space observatory