chemistry Past Questions And Answers

811

Smoke consist of?

A. solid particles dispersed in liquid
B. solid or liquid particles dispersed in gas
C. gas or liquid particles dispersed inliquid
D. liquid particles dispersed inliquid

View Discussion (0)JAMB 1990

812

(a) Consider the following compounds: (i) What is the relationship between the compounds labeled A and B? (ii) Name each of compounds A and B. (iii) Will the chemical properties of compounds A and B be the same? (iv) Give the reason for the answer stated in 2(a)(ii).

(b)(i) Give two characteristic features of boiling, (ii) What would be the effect of each of the following conditions on the boiling point of water?I. Addition of crystals of sodium chloride. II. Reduction of the atmospheric pressure. (iii) State one way in which boiling differs from evaporation.

(c)(i) Differentiate between an unsaturated solution and a saturated Solution. (ii) State two ways by which a saturated solution could be made to dissolve more solute. (iii) State one factor that could affect the solubility of a solid in a liquid. (d)(i) Define the term mole .

(ii) Consider the following reaction equation: MgO + 2HCI → MgCl\(_2\) + H\(_2\). What mass of magnesium Oxide is needed to neutralize 25.0 cm3 of 0.1 mol dm-3 hydrochloric acid? [O= 16.0; Mg = 24.0]. (e) State three physical properties of metals.

Explanation

a)(i) They are geometric/cis-trans isomers; (ii) Compound A: Trans 1, 2- dichloroethene, Compound B: Cis - 1,2- dichloroethene. (iii) The chemical properties will be the same (iv) because they both contain the same functional group; - they have same type of atoms connected in the same way

b)(1)- boiling takes place at a specific temperature; - boiling takes place throughout the liquid, - bubbles are formed vapour pressure is equal to atmospheric pressure (ii) I. It increases the boiling point of the water, ii. It lowers the boiling point of the water.

BOILING	EVAPORATION
Occurs throughout the liquid	Occurs only at the surface of the liquid
Occurs at a particular constant temperature	Takes place at all temperatures
Has no cooling effect	Has a cooling effect
Exothermic	Endothermic
Occurs using external source of heat/not spontaneous	Occurs using internal energy/spontaneous
Bubbles are observed	Bubbles are not observed
Not affected by humidity	Affected by humidity
Fast process	Slow process

Unsaturated solution	Saturated solution
Can dissolve more solute at that temperature	Cannot dissolve any more solute at that temperature
Does not contain undissolved solute at that temperature	Contains undissolved solute at that temperature

C. (ii) -increasing the temperature; - increasing the volume of solvent (iii.) - temperature; - volume of solvent; - nature of solute; - nature of solvent

D. (i) The amount of substance containing 6.02 x 10\(^23\) particles of that Substance/amount of substance containing as many particles as there are atoms in 12g of carbon 12.

(ii) n (HCI) = 25.0 x 10 dm3 x 0.1 moldm3, n (HCI) 2.5 x 10\(^-3\) mol.

From the equation of the reaction:

Mole of HCI = 0.025 x 0.1 = 0.0025

-->mol of MgO = 0.0025 / 2 = 0.00125mol

Molar mass of MgO = 24+ 16 =40

mass of MgO= 0.00125x 40 = 0.05g

(e) - are malleable,

-are ductile;

- are lustrous;

- have high melting point/boiling;

- have high tensile strength/hard Strong

-high density;

-solids at room temperature except mercury; -

good conductors of heat;

-good conductors of electricity: sonorous

View Discussion (0)WAEC 2020 THEORY

813

A solution that contains as much solute as it can dissolve at a given temperature is said to be

A. concentrated
B. saturated
C. supersaturated
D. unsaturated

View Discussion (0)WAEC 2009 OBJ

814

What is the valency of an element with the electronic configuration 2, 8, 7?

A. 7
B. 1
C. 2
D. 3

View Discussion (0)JAMB 2023

815

Which of the following would dissolve in warm dilute H₂SO₄ without effervescence, to give a blue solution?

A. Copper turnings
B. Copper (ll) trioxocarbonate (IV)
C. Copper (ll) oxide
D. Copper alloy

View Discussion (0)WAEC 2001 OBJ

816

28.8cm³ of nitrogen at 15°C is cooled to 0°C at constant pressure, the new volume of nitrogen is

A) 17.4cm³
B) 14.7cm³
C) 27.3cm³
D) 31.7cm³

View Discussion (0)POST UTME FUTO

817

Which of the following properties of covalent compounds is not correct? They

A. are non-electrolytes
B. are mostly gaseous and volatile liquids
C. have low melting point
D. have high boiling points

View Discussion (0)WAEC 2009 OBJ

818

A metal X forms two chlorides with the formulae XCI2 and XCI3. Where is X in the Periodic Table?

A. Group ll
B. Group llI
C. d-block
D. s-block

View Discussion (0)WAEC 2004 OBJ

819

Which of the following metals cannot displace hydrogen from steam?

A) Copper
B) Iron
C) Strontium
D) Lithium

View Discussion (0)POST UTME OAU

820

When a compound X is heated with concentrated tetraoxosulphate(VI)acid, it produces an alkene. X ia an

A. Alkane
B. Alkanol
C. Alkanoate
D. Alkyne

View Discussion (0)WAEC 2016 OBJ