Search our library of IB questions

Top answers

All subjects

Calculate: (a) The amount, in mol, of white phosphorus used, (b) the limiting reagent, (c) the excess amount, in mol, of the other reagent.

P₄(s) + 3OH^-(aq) + 3H₂O(l) ---> PH₃(g) + 3H₂PO₂^-(aq)
Provided for answering (a): Mass of white phosphorus: 2...

6412 Views

Consider the infinite geometric sequence 25 , 5 , 1 , 0.2 , ... (a) Find the common ratio. (b) Find (i) the 10th term; (ii) an expression for the nth term. (c) Find the sum of the infinite sequence.

QUESTION (a) R = U(n+1)/U(n ) = 5/25= 0.2(b) (i) U(10) = 25 x (1/5)^9 = 0.0000128 (ii) U(n) = 25 x (1/5)^(n-1)(c) S = U(1)/(1-r) = 25/(1-(1/5))=25/(4/5))=125/4=31.25

Answered by Carlota R. • Maths tutor

6019 Views

What cells and in what order take part in the imune response?

https://www.bitpaper.io/go/Tara%20Cell%20recognition/H1OQMML-N

Answered by Thomas Georgas G. • Biology tutor

1499 Views

I am struggling with English: Language & Literature (HL) Paper 2. When I write practice papers, I never know how to structure my work to include the criterion A) knowledge of texts and contexts.

Paper 2 is among the most challenging Lang & Lit assignments, but don’t worry, with enough practice and a clear structure in your head, the 2-hour exam can be about you ‘filling in the blanks’. First ...

Answered by Adam P. • English tutor

2807 Views

Why does the atomic radius of an atom decrease as you go across a period?

The atomic radius is often defined as being one half the distance between the two nuclei in a homonucleur diatomic molecule. In general, there is a decrease in atomic radius as you go across a period. Thi...

Answered by Louise E. • Chemistry tutor

1678 Views