Acids

Question 1

Student prepare 250cm3 of a 0.4moldm-3 starting form magnesium nitrate crystals Mg(NO3)2.6H2O
Describe how the student would prepare the solution giving full details of quantaties, apparatus and method (6)

Answer 1

calculation
* 250/1000 x0.4=0.1mol
* M(Mg(NO3)2 = 148.3
* mass 14.3g
Preparation
* weigh mass of crystals
* dissolve in distilled water
* transfer 250cm3 volumetric flask
* make up the mark with more water so that the bottom of the meniscus is on the mark
detail
* 2 or more decimal place balance
* rinse beaker and transfer waahing to flask
* use of dropping pipette when filling to the mark
* stopper invert several times to mix

Question 2

What is meant by the term alkali (1)

Answer 2

release OH- ions in aqueous solution

Question 3

What is meant by the term standard solution (1)

Answer 3

a solution of known concentration

Question 4

What is meant by an acid and a weak acid (1)

Answer 4

• acid releases H+ ion and weak acid partially dissociates

Question 5

Outline a method to plot a graph of mass against time for strontium carbonate and dilute nitric acid (3)

Answer 5

• flask and balance and stopwatch
• record mass at time intervals
• 10-50s

Question 6

What is meant by the term base (1)

Answer 6

substance that acceps H+ ions

Question 7

What is meant by the term alkali (1)

Answer 7

releases OH- into aqueous solutions

Question 8

A student wants to prepare a solution of calcium nitrate from calcium carbonate what reagant would they use and the equation (2)

Answer 8

• nitric acid
• CaCO3+2HNO3 ->Ca(NO3)2+H2O+CO2

Question 9

a typical metal reacts with dilute sulfuring acid to form a salt what is the second product (1)

Answer 9

hydrogen

Question 10

How is a salt formed when a metal reacts with sulfuric acid (1)

Answer 10

a hydrogen ion has been replaced from a metal ion

Question 11

Write a formula of cerium (III) ulfate and explain what happens in reaction in term of number of electrons tranferred (2)

Answer 11

• Ce2(So4)3
• cerium loses three electrons to form a 3+ ions

Question 12

The student is not confident that their titre is accurate uggest what the tudent should do next to reduce the effect of any random errors (2)

Answer 12

• repeat tirtations until two titrations are concordant
• calculate mean titre form concordant results