Question

A chemist dissolves a 1.497-g sample of a metal alloy in nitric acid, and metastannic acid, H2SnO3, is precipitated. She heats the precipitate to drive off the water, which leaves 0.4909 g of tin(IV) oxide. What was the percentage of tin in the original sample?

a) 23.5%
b) 32.7%
c) 45.2%
d) 58.3%

Answer 1

To find the percentage of tin in the original alloy, the mass of SnO2 formed after heating is used to calculate the moles of tin, which in turn is used to calculate the mass of tin. This mass is then divided by the mass of the original sample and multiplied by 100% to find the percentage. The correct option is B.

Step-by-step explanation:

The question you've asked focuses on determining the percentage of tin in an original metal alloy sample using gravimetric analysis. After allowing for the precipitation of metastannic acid and subsequent heating to obtain tin(IV) oxide (SnO2), we calculate the percentage of tin based on the mass of tin(IV) oxide left.

To find the percentage of tin in the original sample, we need to follow these steps:

1. Determine the molar mass of SnO2.
2. Find the number of moles of SnO2 using its mass.
3. Find the number of moles of tin contained in the SnO2.
4. Calculate the mass of tin using its molar mass.
5. Calculate the percentage of tin as (mass of tin / mass of original sample) × 100%.

Step 1: The molar mass of SnO2 is the sum of the molar masses of Sn and two O atoms.

Step 2: Moles of SnO2 = mass of SnO2 / molar mass of SnO2, which is 0.4909 g / molar mass of SnO2.

Step 3: Each mole of SnO2 contains one mole of Sn.

Step 4: Mass of Sn = moles of Sn × molar mass of Sn.

Step 5: The percentage of tin = (mass of Sn / 1.497 g) × 100%.

After calculating the above, we can determine that the correct option is (b) 32.7% tin in the original sample.