Top answers

X^2 -25 Find the solution to this equation.

candidate should recognise the equation is a difference between two squares. the next step is to factorise: square root of 25 is 5 (x-5)(x+5) = x^2-25 x= -5 x= 5
JD
Answered by Jakub D. • Maths tutor
3629 Views

For the reaction (hydrochloric acid + magnesium -> magnesium chloride + hydrogen) what would happen to the rate of reaction if the solid magnesium was cut into smaller pieces? Explain the change (4)

By cutting the solid magnesium into smaller pieces you are increasing the surface area and also making a larger surface area to volume ration. Increasing the surface area increases the rate of reaction as th...
AR
Answered by Abigail R. • Chemistry tutor
8312 Views

Find 100 consecutive natural numbers, each of which is composite

So this is the sort of quesition where you will spend a while thinking about it, probably feel a little silly you haven't gotten it yet, then go "aha!", write down the answer and move on. It's all ...
GV
Answered by Gabriel V. • STEP tutor
1854 Views

If x^2 + 2y = -14 and y = 4x + 1 , by using the quadratic formula, find the possible values for x.

First the equation for y must be substituted into the first equation to give a quadratic equation in x. Rearrange this equation so that the left-hand side equals 0. Using the quadratic formula the possible v...
RW
Answered by Rachael W. • Maths tutor
2965 Views

Calculate the enthalpy of combustion of 1 mol of ethanol using mean bond enthalpy (kJ/mol) data: C-C (347), C-H (413), C-O (358), O-H (464), O=O (498), C=O (805)

First we need to construct the equation of the combustion: C2H5OH(l) + 3O2(g) --> 2CO2(g) + 3H2O(l)Use aid of structural formulaLeft hand side (endothermic - requires energy):5(413) + 347 + 358 + 464 + 3(...
LL
Answered by Lewis L. • Chemistry tutor
14606 Views