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How do you expand brackets?

Let's have a look at a pair of brackets: (a+b)(c+d)To expand these brackets each value in one bracket must be multiplied by all values in the other bracket separately then added together. So we have: ac+ad+b...
PB
Answered by Phoebe B. • Maths tutor
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How do I work out how a number is written in fraction form, if it is a reoccurring decimal?

If I have a reocurring decimal I use a special trick to work it out as a fraction. The trick is to try and cancel out the reocurring bit by multiplying by 10 several times and then using subtraction. E.g. 7....
JD
Answered by Jasmin D. • Maths tutor
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What is meant by equilibrium

When a reaction is in equilibrium, it means the rate of the forward reaction is equal to the rate of the backwards reaction. The concentrations of the reactants and products remain constant, but this does no...
CI
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Reaction between a metal and acid gives?

Metal + Acid --> Metal salt + H2 (g)E.g. Cu + HCl --> CuCl2 + H2
CI
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The student did another experiment using 20 cm3 of sodium hydroxide solution with a concentration of 0.18 mol/dm3 . Relative formula mass (Mr) of NaOH = 40 Calculate the mass of sodium hydroxide in 20 cm3 of this solution.

Answer= 0.144g Working out: mol= conc x volume (in dm^3)mass = mol x RFFSo,mol = 0.18 x (20/1000) = 0.0036mol Mass= 0.036 x 40 = 0.144g
CI
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