Question

Lithium metal reacts with water to produce hydrogen gas and the corresponding metal hydroxide.

A) Write the balanced chemical equation and describe the type of reaction
B) How many grams of hydrogen gas will be formed by the complete reaction of 80.57 g of lithium with water?
C) How many grams of water will be used to produce the hydrogen gas above?

Please post your work so I can see where I'm going wrong. Thank you!!

Answer 1

A)

2 Li + 2 H2O —> 2 LiOH + H2

B)

Molar mass of Li = 6.968 g/mol

mass of Li = 80.57 g

mol of Li = (mass)/(molar mass)

= 80.57/6.968

= 11.56 mol

According to balanced equation

mol of H2 formed = (1/2)* moles of Li

= (1/2)*11.56

= 5.781 mol

Molar mass of H2 = 2.016 g/mol

mass of H2 = number of mol * molar mass

= 5.781*2.016

= 11.66 g

Answer: 11.7 g

C)

According to balanced equation

mol of H2O formed = moles of Li

= 11.56 mol

Molar mass of H2O,

MM = 2*MM(H) + 1*MM(O)

= 2*1.008 + 1*16.0

= 18.016 g/mol

mass of H2O = number of mol * molar mass

= 11.56*18.02

= 208 g

Answer: 208 g