Compounds combining question?

Question

For a certain sodium compound, one atom of sodium combines with one atom of hydrogen. 10g of sodium would completely combine with how many grams of hydrogen atoms? How is this problem done? Will i need to convert to moles?

Answer 1

Na + H ===> NaH (sodium hydride)

10 grams of sodium is 10/22.99 moles or 0.435 moles of sodium

so you need 0.435 moles of Hydrogen ATOMS (not hydrogren gas, which is H2), or

0.435 * 1.00794 g/mole = 0.438 grams of hydrogen

Answer 2

Okay, first find out how many moles of sodium are in 10 grams (divide 10 by the atomic mass of sodium). Next, figure out the atomic mass of hydrogen and multiply this by the number of moles you just calculated and that will be you answer in grams.

Answer 3

Always start by writing a correctly balanced equation (and make sure the equations are right):

2Na + H2 gives 2NaH

Note: H can exist as a negative one; it is then called a "hydride".


Step 2: Determine the relative ratio of moles. Here it is saying:

2 mole of Na + 1 mole H2 gives 2 moles NaH


so you gotta have 2 moles of Na for every one mole of H2. That's a 2 to 1 (2:1) ratio.

Now calculate how many moles of Na you have if you have 10 g Na.

moles Na = 10 g Na / 23 g/mol Na

= 0.4 mol Na

Using the ratio of 2:1, you're only gonna need half that number of moles of H2

= 0.4 mol Na / 2 mol H2/mol Na

= 0.2 mol H2

So how many grams is 0.2 mol of H2 equal too?

grams H2 = moles H2 x MW H2

= 0.2 mol H2 x 2 g/mol H2

= 0.4 g H2

That's the answer!

[Sorry Dave Star, you gotta use significant figures, and you didn't. I'm right, you're close, but not right. You also didn't write the formulas and equation correctly or balance it either]. ]