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Q3. A third beaker, C, contains 100.0 cm^3 of 0.0125 mol/dm^3 ethanoic acid ( Ka = 1.74 × 10^−5 mol/dm^3 at 25 ºC). Write an expression for Ka and use it to calculate the pH of the ethanoic acid solution in beaker C.

A3. Ethanoic acid is a weak acid with the formula CH3COOH. It will dissociate into H+ and CH3COO- therefore the expression for Ka is [H+][CH3COO-]/[CH3COOH] The [H+] = [CH3COO-] and so the expression becomes...
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A ball is thrown vertically upwards with a speed of 24.5m/s. For how long is the ball higher than 29.4m above its initial position? Take acceleration due to gravity to be 9.8m/s^2.

To find how much time the ball spends above 29.4m, we need to find the times at which the ball is at 29.4m above its starting point, and then calculate the difference between these times. Acceleration is con...
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Answered by Sherry B. • Maths tutor
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Q2. Calculate the pH of the solution formed after 50.0 cm^3 of 0.0108 mol/dm^3 aqueous sodium hydroxide are added to beaker B. Give your answer to 2 decimal places

A2. First thing to work out is the moles of NaOH added, since moles = concentration x volume, = 0.0108 mol/dm^3 x 50ml, but need volume to be in units of Litres to match with the units of dm^3 so the formula...
TD
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Q1. Two beakers, A and B, each contain 100.0 cm^3 of 0.0125 mol/dm^3 nitric acid. Calculate the pH of the solution formed after 50.0 cm^3 of distilled water are added to beaker A. Give your answer to 2 decimal places.

A1. First it is important to know that nitric acid (HNO3) is a strong acid and so [HNO3] = [H+] Beaker A contains 100cm^3 = 100ml Final volume is 150ml (50cm^3 of distilled water is added to beaker A) So, (1...
TD
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What is the difference between permutations and combinations?

The main difference is that order of objects matters for permutations. Both involve choosing k objects from a group of size n. Permutations are used to calculate the amount of possible ways a group can be ma...
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Answered by Oliver P. • Maths tutor
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