Solve the following problems: A cake recipe uses dry ingredients, namely 75 g of sugar. Class 9

Solve the following problems: A cake recipe uses dry ingredients, namely 75 g of sugar. Class 9

Question 1.

Solve the following problems: Class 9

(i) A cake recipe uses dry ingredients, namely 75 g of sugar for 420 g of all purpose flour and 5 g of sodium hydrogen carbonate. Express the concentration of each component in the mixture using an appropriate method.

(ii) A brass alloy contains 70% copper by mass. Calculate the quantities of copper and zinc present in 120 g of brass.

Answer:

(i) Total mass of mixture = 75 + 420 + 5 = 500 g.

Since all components are solids, we use mass by mass percentage (% m/m).

Sugar: % m/m = ([latex]\frac{75}{500}[/latex]) × 100 = 15% m/m

All-purpose flour: % m/m = ([latex]\frac{420}{500}[/latex]) × 100 = 84% m/m

Sodium hydrogen carbonate: % m/m = ([latex]\frac{5}{500}[/latex]) × 100 = 1% m/m

(ii) Brass contains 70% copper and.(100 - 70) 30% zinc by mass.

Mass of copper = ([latex]\frac{70}{100}[/latex]) × 120 = 84 g

Mass of Zinc = ([latex]\frac{30}{100}[/latex]) × 120 = 36 g

Verification: 84 + 36 = 120 g