A Big Mac hamburger contains 5.50 times 10^5 calories. How many kilojoules does

Question

A Big Mac hamburger contains 5.50 times 10^5 calories. How many kilojoules does a Big Mac contain? (1 cal = 4.184J) How many atoms in the 60.0g of Balance the following equation using proper coefficients. Be_2C + H_2O rightarrow Be(OH)_2 + CH_4 According to the balanced chemical equation in a), if150g of H_2O reacted with 15.00g of Beryllium, which is the limiting reagent in this reaction, Be or H_2O? Justify your answer with calculations. Calculate the theoretical yield of Be(OH)_2 in b). An analysis of the compound gives the following composition by mass: H: 2.1 percentage, O: 65.3 percentage and 32.6 percentage S Calculate its empirical formula.

Explanation / Answer

IV) 1 cal = 4.184 J

The heat given by Big Mac = 5.5x105cal x4.184 J/1cal

= 2.301x 106J

V) one mole of AgCl contains two moles of atoms

Thus moles of AgCl = mass / molar mass

= 60.0g / 143.5g/mol

thus the number of atoms in 60.0g of AgCl = (60.0g / 143.5g/mol) x 2 x 6.02 x 1023

= 5.035x1023

VI) a)the balanced equation is

Be2C + 4H2O --------------> 2 Be(OH)2 +CH4

b) 15g/30g/mol 150g/18g/mol 0 0 initial moles

To know the limiting regent

0.5 8.3

ratio of moles

0.5/1 =0.5 8.3/4=2.07

Thus Be is the limiting reagent , thus the product is calculated from limiting reagent

so the product Be(OH)2 formed = 2x0.5 moles

mass of product = moles x molar mass

= 2x0.5 mol x 43g/mol

= 43 g

vii) element H O S

mass % 2.1 65.3 32.6

moles 2.1 4.08 1.01

ratio of moles 2 4 1

Thus the empirial formula is H2SO4

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