How many atoms are there in 250g of tin?

Avariable that is not being directly tested during an experiment should be

Hydrogenation reactions, in which h2 and an "unsaturated" organic compound combine, are used in the food, fuel, and polymer industries. in the simplest case, ethene (c2h4) and h2 form ethane (c2h6). if 140 kj is given off per mole of c2h4 reacting, how much heat (in mj) is released when 12 kg of c2h6 forms?

What is the value of the standard enthalpy of formation of an element in its most stable form?