Summarize your observations and reactions that occurred when zinc and calcium ar

Question

Summarize your observations and reactions that occurred when zinc and calcium are the added to 6 M hydrochloric acid. What is the reaction when zinc and calcium are to water? Compare the reactions in the first part of this lab and comment on the gas that is produced in the reactions Calculate the formula for the calcium hydroxide by using the molar mass and exact sample mass of calcium to determine the number of moles used in your titration. Next calculate the moles of HCl that was used to titrate each sample. Use this information to calculate the mole ratio between HCl and Ca for each sample. Remember from Equation 3.4 that one mole of HCl reacts with one mole of hydroxide; therefore, how many moles of hydroxide must have been produced for every mole of calcium that reacted? From your experimental result, what must be the formula for the calcium hydroxide produced in the reaction of calcium with water? Remember that the point is to find the experimental formula for the calcium hydroxide. Your calculations must be done as if you don't know the actual formula!

Explanation / Answer

Zinc and calcium metal reacts with 6M HCl to produce hydrogen gas.

Zn + HCl ------> ZnCl2 + H2

Ca + HCl ------> CaCl2 + H2

Zinc and calcium metal reacts with water to produce hydrogen gas.

Zn + H2O ------> ZnO + H2

Ca + 2H2O------> Ca(OH)2 + H2

For titration 2

Mass of Ca used (given) = 0.968 g

Number of moles of Ca = Mass of Ca/ Atomic mass of Ca

= 0.968 g / 40.078 g mol-1

= 0.0242 mol

Number of moles of HCl = Concentration X Volume

= 6 mol L-1 X 6.2 X 10-3 L

= 0.0372 mol

HCl: Ca ratio is 0.0372 mol : 0.0242 mol

= 1.5/1

1 HCl molecule reacts with 1 hydroxide molecule

Therefore there must be 1.5 hydroxide molecules per calcium

Based on these calculations, the formula for calcium hydroxide will be

Ca (OH)1.5 or Ca2(OH)3

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