Quiz & Worksheet - Reactants in Chemistry | Study.com - Free Printable

Let’s go step by step through each question.

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Question 1: Chemical reactions are written _____.

In chemistry, we always write chemical reactions with the starting materials (reactants) on the left, and the products (what you get after the reaction) on the right. The arrow points from left to right to show the direction of the reaction.

So, correct answer: from left to right

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Question 2: Which of the following best describes a reactant?

Reactants are the substances you start with — they’re like the “ingredients” before the reaction happens. After the reaction, they turn into new substances called products.

Looking at the options:

- “Raw materials for a reaction” → YES! That’s exactly what reactants are.
- “Substances that result from a reaction” → No, those are products.
- “Substances that have recombined into new combinations” → This sounds more like products too.
- “Substances with atoms that do not recombine” → Not accurate; in reactions, atoms *do* recombine.

Correct answer: Raw materials for a reaction

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Question 3: Which correctly identifies the reactants for this reaction?

Reaction given:

> CH₄ + Cl₂ → (with UV light) → CH₃Cl + HCl

The reactants are always on the left side of the arrow. So here, it’s CH₄ and Cl₂.

Products are on the right: CH₃Cl and HCl.

So, correct choice: CH₄ + Cl₂

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Final Answer:
1. from left to right
2. Raw materials for a reaction
3. CH₄ + Cl₂