What mass in grams would 5.7L of hydrogen gas occupy at STP?

 The correct answer is:  " 0.54 g " .

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Explanation:

Note that "hydrogen gas" is:  

H₂ (g)  ;   that is:  a "diatomic element" (diatomic gas) ;

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The molecular weight of "H" is:  1.00794 g ;

   (From the Periodic Table of Elements).

So, the molecular weight of:  H₂ (g)  is:

    " 1.00794 g * 2  = 2.01588 g ; {use calculator) ;

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Note the conversion for a gas at STP:

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  1 mol of a gas = 22.4 L gas;

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i.e. " 1 mol / 22.4 L " ;

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So:     " 5.7 L H₂ (g)  

The "L" ("literes" cancel out to "1" ;  since "L/L = 1 ;

The "mol" (moles) cancel out to "1" ; since "mol/mol = 1 ;

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and we are left with:

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 [5.7 * 2.104588 g ] / 22.4  =  ?  g ;

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→ [ 11.9961516  g ] / 22.4 =

          0.53554248214  g ;l

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We round this value to:  " 0.54 g " ;

 → since "5.7 L " has 2 (two) significant figures;  

     22.4 is an exact number conversion;

     and "5.7 L" has fewer significant figures than:

    " 2.104588 " ; or:  " 1.00794 " .

  → as such: We round to "2 (two) significant figures."

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Hope this is helpful.  Wishing you the best in your academic endeavors!

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for step 7 table c on the lab "newtons law of action"   the average time it took the car to travel .25 meters   was 1.92 seconds.

the average time it took the car to travel 0.50 meters was 2.61 seconds

hope this : )

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