Percentage Composition (Nat 5)

What percentage of oxygen is in NaOH?

• 55%

• 36%

• 40%

• 67%

Answer explanation

The formula mass of NaOH is 40 g.

The mass of 1 oxygen is 16 g.

% comp= 16/40 x 100 = 40%

Eesha, Anaya, and Mia are working on a chemistry project where they need to determine the percentage of manganese in KMnO4. Can you help them figure out what percentage of manganese is present in KMnO4?

• 34.8%

• 12.5%

• 56.2%

• 78.9%

Answer explanation

K= 39

Mn=55

O4=64

total= 158

%=(55/158) x 100

= 34.8 %

Kiara, Aarav, and Arjun are working on a chemistry project. They have a sample of K2CO3 and they need to calculate the percentage of potassium in it. Can you help them?

• 45.6%

• 62.3%

• 38.8%

• 56.5%

Answer explanation

Mass of potassium= 2 x 39 = 78

Formula Mass = 138

% = 78/138 x 100

=56.5

Rachel and Ravi are working on a chemistry project. They have a sample of H2O and they need to calculate the percentage of hydrogen in it. Can you help them?

• 9.5%

• 8.9%

• 10.0%

• 11.1%

Aditi, Aman, and Ananya are working on a biology project. They have a sample of C6H12O6 and they need to calculate the percentage of carbon in it. Can you help them?

• 40.0%

• 43.1%

• 38%

• 36%

Answer explanation

formula mass = 180g

mass of carbon = 72 g

% = 72/180 x 100 = 40%

Brian and Sara are working on a chemistry project. They have a sample of H2SO4 and they need to calculate the percentage of sulfur in it. Can you help them?

• 29.1%

• 46.2%

• 32.7%

• 31.3%

Answer explanation

GFM = 98 g

mass sulfur = 32 g

% = 32/98 x 100

=32.7 %

What percentage of hydrogen is in NH3?

• 17.6%

• 14.3%

• 18.2%

• 15.4%

Robyn and Anya are working on a chemistry project. They have a sample of Na2CO3 and they need to calculate the percentage of sodium in it. Can you help them?

• 34.4%

• 57.6%

• 43.4%

• 50.5%

Answer explanation

formula mass = 106

mass of sodium = 2 x 23 = 46g

%= 46/106 x 100 = 43.4%

Arnav, Riya, and Aarushi are working on a chemistry project where they need to determine the percentage of chlorine in NaCl. Can you help them figure out what percentage of chlorine is present in NaCl?

• 60.7%

• 45.5%

• 52.4%

• 70.9%

What percentage of oxygen is in H2O?

• 85.7%

• 88.9%

• 89.6%

• 86.5%