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Sodium hydroxide reacts with hydrochloric acid - OCR Gateway - GCSE Chemistry: Combined Science - Question 16 - 2018 - Paper 1
Question 16
Sodium hydroxide reacts with hydrochloric acid. Sodium chloride and water are made. (a) Write a word equation for this reaction. (b) A student adds 5cm³ of hydroc... show full transcript
Worked Solution & Example Answer:Sodium hydroxide reacts with hydrochloric acid - OCR Gateway - GCSE Chemistry: Combined Science - Question 16 - 2018 - Paper 1
Step 1
Step 2
Calculate the mean temperature for experiment D.
Answer
To calculate the mean temperature for experiment D, we need the temperatures recorded during the three trials of this experiment. Assuming the values were 34.0°C, 34.5°C, and 34.1°C:
Mean Temperature = ( \frac{34.0 + 34.5 + 34.1}{3} = 34.2 , ^{\circ}C )
Step 3
Describe the pattern of the highest temperature reached during experiments A to C.
Answer
The temperature generally increases as the volume of HCl increases from experiment A to C. In experiment A, the highest temperature is 29.3°C, which rises to 34.5°C in experiment B, and reaches 37.3°C in experiment C. This indicates that the reaction of HCl with NaOH becomes more exothermic with greater acid volumes.
Step 4
Describe the pattern of pH at the end of the reaction for experiments A to D.
Answer
The pH at the end of the reaction generally decreases as the volume of HCl added increases. Experiment A has a pH of 12.0, indicating a strongly basic solution, whereas the pH drops to 10.5 in experiment D, reflecting a more acidic environment as more HCl is used in each trial.