Question

Percentage of Se in peroxide anhydrous enzyme is 0.5% by weight(At.wt.=78.4)then, minimum molecular weight of peroxidase anhydrous enzyme is:
A. $1.568\times {{10}^{4}}$
B. $1.568\times {{10}^{3}}$
C. $15.68$
D. $2.136\times {{10}^{4}}$

Answer 1

Hint: Always remember that percent means this much amount is present in 100.
- The percent composition of any compound can be calculated with the molecular formula to divide the mass of each element found in one mole of the compound by the total molar mass of the compound. The same concept we will apply here.

Complete step by step answer:
- We are given a peroxide anhydrous enzyme in which 0.5% of Se is present.
0.5% means we can assume that 0.5g of Se is present in 100g of enzyme.
- Now we can say that 0.5g of Se is present in 100g enzyme, therefore 78.4g will be present in=$\dfrac{100}{0.5}\times 78.4$=1.5680 or $1.568\times {{10}^{4}}$.
So, Correct answer is option A

Additional Information:
> Selenium is a chemical element with the symbol Se and its atomic number is 34.
> It is a semiconductor which has similarities as arsenic.
> It is found in metal sulfide ores where it partially replaces the sulfur.
> The main commercial uses of selenium are glassmaking, pigments.
> As it is semiconductor so it is used in photocells.
> Selenium salts are toxic in large amounts, but trace amounts are necessary for cellular function in many organisms, including all animals.

Note: Remember one thing when you are solving such types of questions, if you are taking any value in percentage then take it as in parts of 100, and when you are not taking it in percentage then always convert percentage into numerical value.