Chemical Reactions Quiz

Chemical Reactions: ten questions on mass, mole ratios, and reaction patterns. Includes calculations; answers explained.

Free, with no sign-up.

For High school students and adults reviewing the topic.

About 10 minutes. 10 questions.

How does it work?

Choose one answer or enter a number in the stated unit, then check it.
Read the explanation before continuing.
Round only the final answer to the precision requested.

What will you get?

See your score and review the reasoning behind each answer.

Question 1A sealed vessel contains 17 g of one reactant and 29 g of another. Nothing enters or leaves. Find the total mass after reaction in g, rounded to two decimals.

Enter a number in g.

Answers within 0.005 g of the expected value are accepted.

Question 2For 2H2 + O2 → 2H2O, 7 mol of hydrogen reacts completely with excess oxygen. Find the water formed in mol, rounded to two decimals.

Enter a number in mol.

Answers within 0.005 mol of the expected value are accepted.

Question 3For 2H2 + O2 → 2H2O, oxygen is limiting at 3.5 mol and hydrogen is in excess. Find the water formed in mol, rounded to two decimals.

Enter a number in mol.

Answers within 0.005 mol of the expected value are accepted.

Question 4Which coefficient sequence balances N2 + H2 → NH3 using the smallest positive whole numbers?

1, 3, 21, 1, 12, 3, 21, 2, 2

Question 5A solid melts while its molecules keep the same identity. How should that change be classified?

A decomposition reaction splitting the moleculesA physical change in state without new substancesA synthesis reaction making a different compoundA nuclear change altering the atomic nuclei

Question 6A single compound breaks down into simpler substances on heating. Which reaction pattern fits?

Decomposition into products from one reactantSynthesis of a compound from several reactantsPrecipitation from mixing two ionic solutionsNeutralization through proton transfer between an acid and base

Question 7Two clear ionic solutions form an insoluble solid when mixed. What type of reaction does that observation describe?

Melting that converts the dissolved ions into a liquidEvaporation that leaves solid after the solvent boils awayCombustion that burns the solvent in excess oxygenPrecipitation that removes dissolved ions into a solid

Question 8A reaction releases more energy when product bonds form than it absorbs breaking reactant bonds. What is the net result?

Energy transfers from the surroundings overallBond breaking supplies the released energyEnergy transfers to the surroundings overallProduct formation absorbs the excess energy

Question 9Bubbles appear in a warming liquid. What observation would distinguish a reaction from simple boiling most directly?

A count of bubbles rising through the liquidA record that the liquid temperature increasedA photograph showing bubbles reaching the surfaceA chemical analysis identifying a newly formed gas

Question 10A catalyst helps a closed reversible reaction reach equilibrium sooner. What remains unchanged at the same temperature?

The time taken to reach the equilibrium compositionThe equilibrium composition under the same conditionsThe effective activation barrier on the route actually takenThe rates before equilibrium throughout the entire process

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