NY Regents Chemistry Exam June 2022
In a titration using a pH meter, 16.0 milliliters of 0.18 M NaOH(aq) exactly neutralizes a 24.0-milliliter sample of HCl(aq) in a flask. During this laboratory activity, appropriate safety equipment was used and safety procedures were followed. catalyst 61. State the number of significant figures used to express the volume of the HCl(aq) solution. [1]
Explanation:
All non-zero digits are significant. This means all numbers: 1,2,3,4,5,6,7,8, and 9 are significant. For example 5.67 has 3 significant figures.
All zeroes in between non-zero numbers are significant. For example zero in 303 is significant.
Leading zeroes (zeroes to the left of a number) are not significant. For example: 0.0009 has only one significant figure (9) since all of the zeroes to the left of it are not significant.
Trailing zeros to the right of a decimal point are significant. For example zeroes in 3.400 are significant.
Answer: 3
62. Identify the negative ion in the NaOH(aq) used in the titration. [1]
Explanation: NaOH is made of two ions: Na+ and OH- (hydroxide)
Answer: OH- (hydroxide)
63. Compare the number of moles of hydronium ions to the number of moles of hydroxide ions in the titration mixture when the HCl(aq) is exactly neutralized by the NaOH(aq). [1]
Explanation: During a titration, when the acid is exactly neutralized by base, the moles of hydronium ions must be equal to the moles of hydroxide ions.
Answer: The number of hydronium ions is equal to the number of hydroxide ions. 64. Complete the equation in your answer booklet for the neutralization reaction by writing a formula for each product. [1]
Explanation:
The reaction between an acid and base always produces water and salt. Therefore, products need to be H2O and what else is left? Na and Cl, making NaCl
Answer: H2O and NaCl
65. Determine the molarity of the HCl(aq) sample based on the titration data. [1]
Explanation: In a titration experiment, we can use the formula MaVa=MbVb to determine an unknown molarity. Ma is molarity of acid. Va is volume of acid. Mb is molarity of base and Vb is volume of base. Let's plug everything in. We get: 24ml (Ma) = 0.18M* 16.0 ml
Answer: 0.12 M