Question

calculate the mass of nacl need to prepare 500 ml its concentration 10%?
o a. 500 g
o b. no of them
o c. 50 g
o d. 5 g

equivalent mass of the base is equal to.........................
o a. no of them
o b. molar mass / no. of replaced h atom
o c. molar mass / no. of acidic (or basic) radical x its valence
o d. molar mass / no. of oh groups

Explanation:

Step1: Define the mass - volume percentage formula

Mass - volume percentage ($w/v$) = $\frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}}\times100$

Step2: Rearrange the formula to find the mass of solute

Given $w/v = 10\%$, volume of solution $V=500$ mL.
We can rewrite the formula as mass of solute $m=\frac{w/v\times V}{100}$

Step3: Substitute the values

$m=\frac{10\times500}{100}= 50$ g

for second question:
The equivalent mass of a base is defined as the molar mass of the base divided by the number of replaceable $OH^-$ groups.

Answer:

C. 50 g