wrong exam questions Flashcards
state and explain two anomalous properties of ice caused by hydrogen bonding.
Ice is less dense than water so molecules in ice are held apart by hydrogen bonds. Ice has a relatively high melting point due to hydrogen bonds being relatively strong so more energy is needed to overcome the hydrogen bonds.
Elements in the periodic table show a periodic trend in atomic radius. State and explain the trend in atomic radius from LI to F.
Trend : decreases from Li to F
explanation : Nuclear charge increases due to the number of protons increasing. Electrons experience the same amount of electron shielding. Greater nuclear attraction on outer electrons or shells OR electrons or shells are attracted more strongly to the nucleus.
Write an equation between group 7 and sodium hydroxide and the conditions this reaction took place in
Cl2 + 2Naoh -> NaclO + NaCl + H20
The conditions it underwent were cold and the sodium hydroxide used was diluted.
A student adds a small volume of aqueous silver nitrate to an aqueous solution of bromide ions in a test tube. The student then adds a similar volume of dilute aqueous ammonia to the same test tube. Describe what the student would see after the addition of aqueous ammonia.
Cream precipitate
Barium has reacted with water. Write the equation. ( this is the same equation for all group 2 elements).
Ba + 2h20 -> Ba(OH)2 + H2
Explain why ice has a lower density than water
When liquid water freezes into ice,the number of hydrogen bonds increases, producing a regular lattice structure. This structure holds the molecules further apart on average than molecules in water which creates empty spaces between the molecules, making ice less dense than water.
Describe what happens to the molecules in ice when it is heated to its melting point.
The molecules gain enough energy to overcome some of the hydrogen bonds holding them in place in the ice crystal.
