general steps for all stoichiometry problems

.. (1) write a balanced equation

.. (2) convert everything given to moles

.. (3) determine limiting reagent

.. (4) convert moles limiting reagent to moles product

.. (5) convert moles product to mass product.. this is theoretical yield

.. (6) % yield = actual mass recovered / theoretical yield * 100%

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in your case, you're working backwards after step 1

.. (1) balanced reaction equation is.... what?

.. (6) actual mass SiC recovered = 500kg... % yield = 65%

.. .. . .----> theoretical yield SiC = __kg

.. (5) __ theoretical kg SiC = __ theoretical moles SiC

.. (4) __ theoretical moles SiC = __ theoretical moles SiO2

.. (3) what's the LR?

.. (2) moles SiO2 --> mass SiO2

and if you've been practicing that dimenisonal analysis you've been studying lately, you can do this all in 1 equation with 4 unit factors.