If you have 0.50 mole of Ca how many atoms are present?

Answer 1

What compound? Please copy your homework questions completely. How else can we help you cheat?

To find the number of moles of oxygen (or any other element), multiply the number of atoms present on the molecule (in subscript) by the number of molecules present in the reaction (in standard script to the left of the molecule)

In this case:

2 H2 + O2 --> 2 H2O

On the reactant side (to the left of the arrow), there are 4 moles of hydrogen present because we have inserted 2 moles of diatomic hydrogen (multiply the subscript 2 by the standard script 2 to the left of the molecule). We can calculate that there are 2 moles of oxygen present because we have inserted one mole of diatomic oxygen. On the products side (the right side of the arrow) we produced 2 moles of water (indicated by the standard script 2 to the left of the molecule) Each molecule of water contains 2 molecules (2 moles) of hydrogen and one molecule (one mole) of oxygen. Thus, we have a balanced equation because this gives us 4 moles of hydrogen and 2 moles of oxygen, just like we had on the reactant side.

The multipliers in standard script to the left of the molecule gives us the molar ratio. 2 moles of diatomic hydrogen react with 1 mole of diatomic oxygen to produce 2 moles of water. Thus, if we were to burn .5 moles of diatomic hydrogen in excess oxygen, we would produce .5 moles of water. This is because, by looking at our chemical equation, we see that the molar ratio of diatomic hydrogen to water is 2:2 (or 1:1). We would have .25 moles of oxygen because the ratio of hydrogen to oxygen is 4:2 (or 2:1).

Were this the question on your homework, the answer would be ".25 moles"

Answer 2

Since 1 mole of ANY substance contains 6.02E23 atoms, 0.50 mol of Ti would have 3.01E23 atoms.