Show your work please!

Find the number of grams of hcl needed to react completely with .50 moles of magnesium.

What are the coefficients to balance the following equation? ba+br=babr2

What sources of error may have contributed to the percent yield not being 100 percent? think about things that may have led to inaccurate measurements or where mass of the product could have been lost if this experiment was conducted in a physical laboratory.