Question

Given, 2.4 moles of lead (II) hydroxide is how many grams?

Answer 1

The answer is obtained when you find the molar mass of the compound given and then followed by the multiplication of this value with the number of moles which is given and that gives the answer in grams.

Complete step by step solution:
From the classes in general chemistry, we have come across the concepts relating to the simple calculations like calculating the mass of the compound by knowing the atomic mass of each element present in that particular compound, calculation of the number of atoms present using Avogadro number and so on.
Let us see some of these concepts in detail so that we can deduce the required answer as per the data given to us.
To calculate the molar mass of the compound given, we have to be familiar with some of the molar masses of the atoms which are used commonly.
- From the periodic table, we can know the masses of each element and then we can multiply that number with the respective number of moles so that the molar mass of the compound is found in grams.
- Now, in the given compound lead (II) hydroxide which is having the chemical formula $Pb{{(OH)}_{2}}$ , there are two atoms of oxygen and hydrogen each.
- We know that the atomic mass of oxygen with atomic number 8 is 16g/mol. Similarly, the atomic mass of hydrogen with atomic number 1 is 1.
- Now, since these two atoms are divalent in nature, their masses are multiplied by 2 and that of lead with atomic number 82 and mass number 207.2g/mol, the total mass of the compound thus can be calculated as,
$207.2+1\times 2+16\times 2\approx 241.2g/mol$
Hence, the molar mass of lead lead (II) hydroxide is 241.2g/mol.
Now, let us multiply this with total number of moles that is with 2.4 moles and the calculation will be, $2.4\times 241.2=578.88g$
Hence, 2.4 moles of lead (II) hydroxide is equal to 578.88 grams

Note:
Note that while calculating the amount in grams from the number of moles given and the molar mass given, Avogadro number is not necessary as this gives the information about total number of atoms present per mole of a substance.