Answer:
[tex]0.75\ \text{M}[/tex]
Explanation:
[tex]C_1[/tex] = Concentration of [tex]Na_2CO_3[/tex]
[tex]C_2[/tex] = Concentration of [tex]HCl[/tex] = 1 M
[tex]V_1[/tex] = Volume of [tex]Na_2CO_3[/tex] = 20 mL
[tex]V_2[/tex] = Volume of [tex]HCl[/tex] = 15 mL
We have the relation
[tex]V_1C_1=V_2C_2\\\Rightarrow C_1=\dfrac{V_2C_2}{V_1}\\\Rightarrow C_1=\dfrac{15\times 1}{20}\\\Rightarrow C_1=0.75\ \text{M}[/tex]
The concentration of [tex]Na_2CO_3[/tex] is [tex]0.75\ \text{M}[/tex].
