1. Which of these is the formula of a reactant in this reaction?
QUESTION:
Consider the chemical equation for the hydrogenation of acetylene: C2H2 + 2H2  C2H6
Which of these is the formula of a reactant in this reaction?
A. C2H2, B. 2H2, C. C2H6
In a chemical equation, formulas of reactants are written left of the arrow; products on the right-hand side
Coefficients are not part of the formula of any substance.
Consider the chemical equation for the hydrogenation of acetylene as shown here.
HIGHLIGHT balanced equation
Which of these is the formula of a reactant in this reaction?
A. C2H2, B. 2H2, C. C2H6
PAUSE
In a chemical equation, formulas of reactants are written on the left-hand side and formulas of products are written to the right of the arrow.
Therefore the reactants in this reaction are C2H2
HIGHLIGHT C2H2
And H2.
HIGHLIGHT H2 (do not highlight coefficient)
And the product is C2H6.
Therefore, the correct answer is choice A. C2H2 is reactant.
Choice C is wrong since C2H6 is a product, not a reactant.
Choice B is wrong because coefficients are not part of the formula of any substance.
CROSS OUT 2 in 2H2
CLICK PAUSE END RECORDING

2. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08