Question and Answer For Chemistry Problems

1) 19.2 grams of Cu(s) reacts with nitric acid solution as equation as follows :



How many volume of gases which is resulted in

(Ar Cu= 64; C= 12; H=1)

ans :

Mol Cu = 19.2 grams : 62 gram/moles = 0.3097 moles

Mol = (2/3) x 0.3097 moles = 0.2064 moles

in it means STP condition so

Volume in STP condition = 0.2064 moles x 22.4 L/moles = 4.62 L

2) In titration of 10 mL with NaOH 0.1 M, we get the concentration of 0.2 M. How many volume of NaOH needed?

ans :

mol = 10 mL x 0.2 mmol/mL = 2 mmol

mol NaOH = 2 x 2 mmol = 4 mmol

so volume NaOH = 4 mmol : 0.1 mmol/mL = 40 mL

3) We can make Hydrogen gas by using this following reaction :

with Ar of Al = 27 g/moles, so How many of grams Al which is needed to form Hydrogen 44.8 L in STP condition?

ans :

Mol Hydrogen = 44.8 L : 22.4 L/moles = 2 moles

Mol Al = (2/3) x 2 moles = 1.333 moles

Grams of Al = 1.333 moles x 27 g/moles = 36 grams