Question

The diagram illustrates the formation of water. The illustration represents which sequence of events?

A) H2 (element) + O2 (element) → H2O (element)
B) H2 (element) + O2 (element) → H2O (compound)
C) H2 (compound) + O2 (compound) → H2O (element)
D) H2 (compound) + O2 (compound) → H2O (compound)

A solution of CuSO4 is labelled 0.01 M. How much CuSO4 in grams, must be used to make 1 liter of solution?
A) 1.120 g
B) 1.595 g
C) 1.6 g
D) 15.0 g

Answer 1

• Pure substances that cannot be divided into simpler substances either by chemical or physical means are known as elements. They are made up of entirely one type of atom.

Thus, hydrogen and oxygen that is
`H_2` and
`O_2` are elements as they are made up of entirely one type of atom.

Pure substance which is made up of two or more different elements combine in a fixed ratio are known as compounds. They can be separated into smaller substances.

Thus, water that is
`H_2O` is a compound as it is made up of two or more different elements.

Hence, option B is correct that is:

`H_2(element)+O_2(element)\rightarrow H_2O(compound)`

• The molarity of the solution is given as:

`Molarity = (number of moles of solute)/(volume of solution in L)` -(1)

`number of moles of solute = (mass of solute)/(Molar mass of solute)`

Molar mass of
`CuSO_4` =
`63.55 + 32.06 + 4* 15.99 = 159.57 g/mol`

Molarity =
`0.01 M` (given)

Volume of solution =
`1 L` (given)

Substituting the formula of number of moles of solute in molarity formula:
`Molarity = ((mass of solute)/(Molar mass of solute))/(Volume of solution in L)`

Substituting the values:

`0.01 M = ((mass of solute)/(159.57 g/mol))/(1 L)`

`mass of solute = 0.01 mol/L* 159.57 g/mol* 1 L`

`mass of solute = 1.595 g`

Hence, option B is correct.