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Use the structure of sodium chloride to explain why it has a high melting point. (2 marks)

There are strong electrostatic forces of attraction between oppositely charged ions within sodium chlorides giant lattice. The strong electrostatic forces must be broken in order to melt sodium chloride. Sig...
EC
Answered by Evie C. • Chemistry tutor
9895 Views

factorise: 3x^2+13x-30

(3x-5)(x+6)factors of 90 (3x30): 1x90, 6x15, 9x10, 5x18and add up to 13 can only be 5 and 1818-5=13 5/3 or 18/3=6 and 5x6=30so must be (3x-5)(x+6) and check by expanding with FOIL method
MS
Answered by Mary S. • Maths tutor
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Why is it that the sum of all natural numbers up to n is 1/2(n)(n+1)?

First let's consider the case of even numbers. Suppose n is even, then it must be double some other number, so we have: n = 2k Where k is another natural number. We want to find out what: 1 + 2 + ... + (n - ...
IM
Answered by Ibrahim M. • Maths tutor
4545 Views

Bob buys a car for £120 after it is reduced by 20% in the sale. What was the original price of the car?

£120 is the price of the car after it has been reduced by 20%. This means that £120 is equal to 80% of the original price.2 ways to work this out:1) £120 = 80 % £ ? =100%therefore: £? = (120 x 100)/8012000/8...
MP
Answered by Mary P. • Maths tutor
5562 Views

what factors determine enzyme activity?

several factors play a role in the rate of an enzyme catalysed reaction. substrate concentration: The amount of substrate in the solution. The higher the concentration of substrate the more frequently they w...
JL
Answered by Jack L. • Biology tutor
3876 Views