0.25 mol of a chemical species weighs 125 g. What is the molar mass of the speci

Question

0.25 mol of a chemical species weighs 125 g. What is the molar mass of the species?

Which of the following equations is balanced? 2N2O5 --> 3N2O4 + O2 2KNO3 --> 2KNO2 + 3O2 NH4NO3 --> 2N2O + 2H2O NH4NO2 --> N2 + 2H2O

Which of the following equations is balanced? 2NaHCO3 --> Na2CO3 + H2O + CO2 P4O10 + 4H2O --> 4H3PO4 2HCl + CaCO3 --> CaCl2 + 2H2O + CO2 2Al + 3H2SO4 --> Al2(SO4)3 + H2

How many H atoms are there in 3.4 g NH3?

How many O atoms are there in 3.2 g O atom?

How many moles is 1.6 g O2 molecule equal to?

How many moles of H atom is 2.0 moles of H2O equivalent to?

Explanation / Answer

Solution:- (1) molar mass = mass in grams/mol = 125g/0.25mol = 500g/mol

(2) A balanced equation has equal number of moles of each atom on both sides.

First equation is...    

2N2O5   --------> 3N2O4 + O2

left side has 4 N where as right side has 6N so this is not balanced.

second equation is...

2KNO3 ----------> 2KNO2 + 3O2

both sides have 2K, 2N but left side has 6 oxygen where as right side has 10 oxygen so it is not balanced.

third equation is...

NH4NO3   --------> 2N2O + 2H2O

left side have 2N where as right side has 4 N so it is not balanced.

NH4NO2 --------> N2 + 2H2O

both sides have 2N, 4H and two oxygens, so it is balanced.

(3) 2NaHCO3 ---------> Na2CO3 + H2O + CO2

both sides have 2Na, 2H, 2C and six oxygen. So, this is balanced.

P4O10 + 4H2O --------> 4H3PO4

both sides have 4P but left side has 8h where as right side has 12H so this is not balanced.

2HCl + CaCO3 ------> CaCl2 + 2H2O + CO2

left side has three oxygen where as right side has four oxygen so it is not balanced.

2Al + 3H2SO4 -------> Al2(SO4)3 + H2

left side has 6 H where as right side has only 2H so it is not balanced.

(4) 3.4 g NH3 x (1mol/17g) x (3mol H/1mol NH3) x (6.022 x 1023 H atoms/1mol H) = 3.6 x 1023 H atoms

(5) 3.2 g O2 x (1mol O2/32g O2) x (2 mol O/1mol O2) x (6.022 x 1023 O atoms/1mol O) = 1.2 x 1023 O atoms

(6) 1.6 g O2 x (1mol/32g) = 0.05 mol O2

(7) 2.0 mol H2O x (2 mol H/1mol H2O) = 4.0 mol H

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