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Chemistry

A Level

How do you decide what the sign of the enthalpy change should be?

You have to think about whether or not energy is being released by the system into the surroundings (exothermic), or whether the system is taking energy up from the surroundings (endothermic).You have to ...

Answered by Ben W. • Chemistry tutor

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Acid HA has a Ka of 2.00 x 10-4mol dm-3. A solution was made by adding 15cm3 of 0.34 M NaOH to 25cm3 of 0.45M HA. Calculate the moles and the concentration of A- and HA in this solution. Using the expression for Ka calculate the pH of the solution

Write the equation: NaOH + HA --> NaA + H₂O. Find the moles of A^-: the moles of A^-= the moles of NaO...

Answered by Hibba S. • Chemistry tutor

6164 Views

An excess of Lead (II) oxide reacts with 175cm3 of 1.5 mol dm3 nitric acid. Calculate the maximum quantity of lead that can be obtained from this reaction.

Write the equation: PbO + HNO₃ --> PbNO₃ + H₂O. Balance the equation: there are two moles of hydrogen (in water) on the right. To bala...

Answered by Hibba S. • Chemistry tutor

8230 Views

Explain, with reference to the electronic transitions involved, how characteristic flame colours of metal ions are formed and why the flame colours are different.

To answer this we need to talk about how electrons move in an atom. Electrons are in energy levels (orbitals) and an electron in the highest unoccupied orbital can be excited to a higher shell when ...

Answered by Isabel K. • Chemistry tutor

4534 Views

The shape around the oxygen atom in butan-2-ol is non linear. Predict the shape and angle of the C-O-H bond giving explanations

This bond can be described as having a non-linear or bent geometry, with a bond angle of approximately 104.5 degrees. It has this angle because the oxygen atom has 2 lone pairs and 2 bonding pairs of elec...

Answered by Samuel D. • Chemistry tutor

21822 Views