Chemistry Semestral Exam Review

What is the electron dot structure for carbon?

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Answer explanation

The electron dot structure for carbon is represented by the symbol C.

Hey there, Hannah, Aiden, and Harper! Let's dive into the world of chemistry. Can you tell me the name of this oxyacid HClO₃ ? Choose the correct option below:

• Chlorous Acid

• Chloric Acid

• Hydrochloric Acid

• Chlorine Hydroxide

Answer explanation

The balanced chemical equation for the reaction is H2 + O2 -> 2H2O. This equation represents the correct combination of hydrogen and oxygen to form water.

Lily, Maya, and Zoe are on a space adventure! They encounter an alien who will only let them pass if they can correctly identify the electron configuration of oxygen. Can you help them?

• 1s2 2s2 2p2

• 1s2 2s2 2p3

• 1s2 2s2 2p4

• 1s2 2s2 2p6

Answer explanation

The electron configuration of oxygen is 1s2 2s2 2p4. This configuration indicates that oxygen has 8 electrons, with 2 in the 1s orbital, 2 in the 2s orbital, and 4 in the 2p orbital. The correct choice is 1s2 2s2 2p4.

James and Noah are having a friendly debate. James says the compound with the formula NaCl is called Calcium chloride, but Noah disagrees. He thinks it's called Sodium chloride. Ava, being the chemistry whiz, knows the correct answer. Can you help Ava prove who is right?

• Calcium chloride

• Magnesium chloride

• Sodium chloride

• Potassium chloride

Answer explanation

The compound with the formula NaCl is Sodium chloride, which is commonly known as table salt.

Maya, Ava, and Michael are having a friendly competition to see who can calculate the percent composition of carbon in C₆H₁₂O₆ the fastest. Can you beat them to it?

• 60%

• 10%

• 40%

• 25%

Answer explanation

The percent composition of carbon in C6H12O6 is 40%. This is calculated by dividing the mass of carbon by the molar mass of C6H12O6 and multiplying by 100.

Zoe, Kai, and Harper are having a science trivia night! They stumbled upon a question that they can't agree on. Can you help them out? What is the molecular mass of H₂SO₄?

• 98.08 g/mol

• 75.84 g/mol

• 110.98 g/mol

• 63.01 g/mol

Answer explanation

The molecular mass of H2SO4 is 98.08 g/mol, which is the correct choice.

Imagine Lily, Benjamin, and Aiden are playing a game of 'Guess the Element' in their chemistry class. Lily picks an element and gives a clue: 'My element is essential for life and its atomic number is the same as the number of legs on an octopus.' What is the atomic number of Lily's element?

• 32

• 4

• 16

• 8

Answer explanation

The atomic number of oxygen in the periodic table is 8. It is represented by the symbol 'O'. Oxygen has 8 protons in its nucleus, which determines its atomic number.

Evelyn, Ava, and William are having a science competition! They're trying to balance the chemical equation: Fe + O2 -> Fe2O3. Can you help them out?

• 4Fe + 3O2 -> 2Fe2O3

• 2Fe + 3O2 -> Fe2O3

• 3Fe + 2O2 -> Fe2O3

• Fe + 2O2 -> Fe2O3

Answer explanation

The balanced chemical equation for the reaction is 4Fe + 3O2 -> 2Fe2O3. This equation ensures that the number of atoms of each element is equal on both sides of the equation, satisfying the law of conservation of mass.

Emma, Anika, and Luna are having a debate about the electron configuration of calcium. Can you help them settle the debate?

• Emma thinks it's 1s2 2s2 2p6 3s2 3p6 4s3

• Anika believes it's 1s2 2s2 2p6 3s2 3p6 3d2

• Luna suggests it's 1s2 2s2 2p6 3s2 3p6 4s1

• Or is it 1s2 2s2 2p6 3s2 3p6 4s2?

Answer explanation

The electron configuration of calcium is 1s2 2s2 2p6 3s2 3p6 4s2. This configuration represents the arrangement of electrons in the energy levels and sublevels of the atom. The correct choice is 1s2 2s2 2p6 3s2 3p6 4s2.

During a science quiz, Luna and Olivia were asked to name the compound with the formula CO₂. Jackson, who was watching the quiz, knew the answer. Can you guess what Jackson was thinking?

• Dioxide carbon

• Carbon dioxide

• Carbon monoxide

• Oxygen carbon

Answer explanation

The compound with the formula CO2 is Carbon dioxide. It consists of one carbon atom bonded to two oxygen atoms.