Question

Please help, super confused and urgent!

Find the empirical formula for a compound with 27.5% K, 37.5% Mn, and 35% O.
Find the empirical formula for a compound with 17.5% Na, 39.7% Cr, and 42.8% O.
Find the empirical formula for a compound with 34.6% C, 3.9% H, and 61.5% O.
Find the empirical formula for a compound with 65.4% C, 5.5% H, and 29.1% O.

Answer 1

Empirical Formulae for;

Compound 1- K5 Mn5 O16

Compound 2- Na2 Cr2 O7

Compound 3- C3 H4 O4

Compound 4- C3 H3 O1

Explanation:

Step 1; as all the element percentages are given in percent assume the total mass of the compound is 100g and take each percentage as grams i.e., 27.5% of K as 27.5 g of K and so on.

Step 2; convert the mass of each element into their mole values by dividing available mass by molar masses.

Molar masses of required elements are as follows; K=39, Mn=55, O=16 C=12, H=1, Na=23, Cr=52.

Step 3; Divide all the values by the smallest mole value. I.e. for compound 1 after dividing the masses by molar masses we get 0.705, 0.681, and 2.187 for elements K, Mn, O respectively. Divide all three values with the least value which is 0.681 and write these values down.

Step 4; Convert all the numbers available into whole numbers by multiplying with suitable values. i.e. 3 if values are 0.33, 2 if values are 0.5 etc.

Step 5; Assign these values to corresponding elements and you will get the above empirical formula.