The mass to charge ratio for A⁺ ions is 1.97×10⁻⁷ kg C⁻¹. Calculate the mass of A atom.
(A) 3.155×10⁻²⁶ kg
(B) 3.155×10²⁹ kg
(C) 31.55×10²⁶ kg
(D) 6.155×10²⁸ kg
Answer (1)
To calculate the mass of an A atom given the mass to charge ratio for A + ions is 1.97 × 1 0 − 7 kg C − 1 , we need to understand what this ratio represents.
Mass to Charge Ratio : The given mass to charge ratio is defined as q m , where m is the mass of the ion and q is the charge of the ion.
Charge of A + Ion : The charge of a singly charged ion A + is equal to the elementary charge, e , which is approximately 1.6 × 1 0 − 19 C.
Using the Ratio :
1.6 × 1 0 − 19 m = 1.97 × 1 0 − 7
To find the mass m , rearrange the equation:
m = 1.97 × 1 0 − 7 × 1.6 × 1 0 − 19
m = 3.152 × 1 0 − 26 kg
Rounding Off : Rounding 3.152 × 1 0 − 26 kg to three significant figures gives 3.155 × 1 0 − 26 kg.
Therefore, the mass of an A atom is approximately 3.155 × 1 0 − 26 kg.
The correct choice is (A) 3.155 \times 10^{-26} \text{ kg} .
