Hydrogen reacts with .771 g of carbon to form .90 g of a compound. What is the mass percent of hydrogen in the compound?

1 Answer
May 7, 2016

Answer:

#14.3%#

Explanation:

In order to find the mass percent of hydrogen in this compound, you must determine how many grams of hydrogen you'd get in #"100 g"# of compound.

In your case, you know that an unknown mass of hydrogen reacts with #"0.771 g"# of carbon to form #"0.90 g"# of hydrocarbon, which is a compound that contains only carbon and hydrogen.

Use the total mass of the hydrocarbon to determine how many grams of hydrogen reacted with the carbon

#m_"hydrocarbon" = m_(C) + m_(H)#

#m_(H) = "0.90 g" - "0.771 g" = "0.129 g"#

Now, if #"0.90 g"# of this compound contain #"0.129 g"# of hydrogen, it follows that #"100 g"# of this compound will contain

#100 color(red)(cancel(color(black)("g hydrocarbon"))) * "0.129 g H"/(0.90color(red)(cancel(color(black)("g hydrocarbon")))) = "14.33 g H"#

So, if #"100 g"# of this compound contain #"14.33 g"# of hydrogen, it follows that the mass percent of hydrogen is

#"mass percent H" = color(green)(|bar(ul(color(white)(a/a)"14.3%"color(white)(a/a)|)))#

I'll leave the answer rounded to three sig figs.