Alkali metals

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Properties of Alkali Metals

Alkali metals are in Group 1 of the periodic table.
They have low melting points and are soft enough to be cut with a knife.
They have low densities and are very reactive.
They are stored in oil to prevent contact with air and water.

Trends Down Group 1

Reactivity increases as you go down the group.
Melting points decrease as you go down the group.
Lithium is less reactive than potassium; caesium is even more reactive.

Reaction with Water

Alkali metals react strongly with water.
The general word equation: alkali metal + water → metal hydroxide + hydrogen.
The metal hydroxides are alkaline (pH > 7).
Reactions become more fierce down the group.

Examples of Reactions

Lithium + water → lithium hydroxide + hydrogen (fizzes).
Potassium + water → potassium hydroxide + hydrogen (ignites hydrogen).
Caesium + water → caesium hydroxide + hydrogen (very vigorous).

Safety Precautions

Demonstrations should be behind a safety screen.
Only small amounts of alkali metal should be used.
Keep alkali metals stored in oil.

Bohr model of a sodium atom (alkali metal) showing electron configuration 2.8.1.

Particle arrangement in solids, liquids, and gases. Alkali metals are solid at room temperature (except mercury).

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练习题

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1.Which group of the periodic table are the alkali metals in?
Easy
- AGroup 1
- BGroup 2
- CGroup 7
- DGroup 0
2.Which of the following is a property of alkali metals?
Easy
- AThey have low melting points.
- BThey have high melting points.
- CThey are very unreactive.
- DThey are hard and cannot be cut with a knife.
3.What is the pH of an alkaline solution?
Easy
- AGreater than 7
- BEqual to 7
- CLess than 7
- DExactly 7
4.Why are alkali metals stored in oil?
Easy
- ATo keep air and water away from them
- BTo keep them cool
- CTo make them easier to cut
- DTo increase their reactivity
5.Complete the word equation: alkali metal + water → ?
Easy
- Ametal hydroxide + hydrogen
- Bmetal oxide + hydrogen
- Cmetal hydroxide + oxygen
- Dmetal oxide + water
6.When lithium reacts with water, what causes the fizzing?
Easy
- ARelease of hydrogen gas
- BRelease of oxygen gas
- CFormation of lithium hydroxide
- DIgnition of the metal
7.As you go down group 1, how does the reactivity of alkali metals change?
Easy
- AReactivity increases
- BReactivity decreases
- CReactivity stays the same
- DReactivity first increases then decreases
8.Which alkali metal has a stronger reaction with water: lithium or potassium?
Easy
- APotassium
- BLithium
- CThey react equally
- DNeither reacts

更多题目

9.In a demonstration of sodium reacting with water, which safety precaution is likely to be taken?
Easy
- AUsing a safety screen
- BUsing large amounts of sodium
- CPerforming the demonstration without goggles
- DAdding water to the sodium instead
10.What is the trend in melting points as you go down group 1?
Easy
- AMelting points decrease
- BMelting points increase
- CMelting points stay the same
- DMelting points first decrease then increase
11.Which of the following is the correct word equation for the reaction of caesium with water?
Easy
- Acaesium + water → caesium hydroxide + hydrogen
- Bcaesium + water → caesium oxide + hydrogen
- Ccaesium + water → caesium hydroxide + oxygen
- Dcaesium + water → caesium oxide + water
12.True or false: Alkali metals are very reactive.
Easy
- ATrue
- BFalse
- COnly lithium is reactive
- DOnly sodium is reactive
13.A student measures the pH of a solution formed when a small piece of an alkali metal is added to water. The pH reading is 13. What does this indicate about the solution?
Easy
- AIt is strongly alkaline.
- BIt is weakly alkaline.
- CIt is neutral.
- DIt is acidic.
14.In an experiment, 0.1 g of lithium is reacted with excess water. The hydrogen gas produced is collected and measured at room temperature and pressure. Which of the following is the most likely volume of hydrogen collected? (Assume 1 mole of gas occupies 24 dm³ at room temperature and pressure; Ar: Li = 7)
Hard
- A0.34 dm³
- B0.17 dm³
- C0.24 dm³
- D0.48 dm³
15.A student is given three unlabelled samples of alkali metals: lithium, sodium, and potassium. They add a small piece of each to water and observe the reactions. Which of the following observations would correctly identify potassium?
Medium
- AIt fizzes gently and produces a gas.
- BIt fizzes vigorously and the gas ignites with a lilac flame.
- CIt sinks to the bottom and reacts slowly.
- DIt produces a white precipitate.
16.The table below shows the melting points of three alkali metals. Which of the following is the most likely melting point of rubidium?
Medium
- A39 °C
- B98 °C
- C180 °C
- D28 °C
17.Which of the following is a property of all alkali metals?
Easy
- AThey are very reactive.
- BThey have high melting points.
- CThey are hard and dense.
- DThey are gases at room temperature.
18.A student writes the word equation for the reaction of sodium with water as: sodium + water → sodium oxide + hydrogen. Is this equation correct?
Easy
- AYes, it is correct.
- BNo, the products should be sodium hydroxide and hydrogen.
- CNo, the products should be sodium oxide and oxygen.
- DNo, the products should be sodium hydroxide and oxygen.
19.The graph shows the trend in melting points of alkali metals down group 1. Which of the following best describes the trend?
Easy
- AMelting point increases steadily down the group.
- BMelting point decreases steadily down the group.
- CMelting point increases then decreases.
- DMelting point remains constant.
20.A student observes that when a small piece of an alkali metal is added to water, it floats and moves around the surface. Which property of alkali metals explains why it floats?
Easy
- ALow density
- BLow melting point
- CHigh reactivity
- DSoftness
21.In a demonstration, a teacher adds a piece of sodium to water. Which of the following safety precautions is most important?
Medium
- AWearing safety goggles
- BUsing a safety screen
- CUsing a small piece of sodium
- DAll of the above
22.Which of the following word equations correctly represents the reaction of caesium with water?
Easy
- Acaesium + water → caesium hydroxide + hydrogen
- Bcaesium + water → caesium oxide + hydrogen
- Ccaesium + water → caesium hydroxide + oxygen
- Dcaesium + water → caesium oxide + water
23.Alkaline solutions have a pH that is:
Easy
- Agreater than 7
- Bequal to 7
- Cless than 7
- Dexactly 14
24.A student compares the reactions of lithium and potassium with water. Which of the following is a correct observation?
Easy
- ALithium reacts more vigorously than potassium.
- BPotassium reacts more vigorously than lithium.
- CBoth react with the same vigour.
- DNeither reacts with water.
25.In a demonstration of the reaction between sodium and water, which safety precaution is most important?
Medium
- AUsing a safety screen
- BWearing gloves
- CUsing a small piece of sodium
- DBoth A and C
26.A student observes that when a small piece of lithium is added to water, it fizzes. What causes the fizzing?
Easy
- ARelease of oxygen gas
- BRelease of hydrogen gas
- CFormation of lithium hydroxide
- DMelting of lithium
27.Complete the word equation: alkali metal + water → ? + hydrogen
Easy
- Ametal oxide
- Bmetal hydroxide
- Cmetal chloride
- Dmetal carbonate
28.In an experiment, 0.1 g of lithium is reacted with excess water. The hydrogen gas produced is collected and measured at room temperature and pressure. Which of the following is the most likely volume of hydrogen gas produced? (Assume 1 mole of gas occupies 24 dm³ at room temperature and pressure; atomic masses: Li = 7, O = 16, H = 1)
Hard
- A0.34 dm³
- B0.17 dm³
- C0.68 dm³
- D0.09 dm³
29.What is the trend in melting points of alkali metals as you go down group 1?
Easy
- AMelting points increase
- BMelting points decrease
- CMelting points stay the same
- DMelting points first increase then decrease
30.A student adds a 0.2 g piece of lithium to excess water and collects the hydrogen gas produced. At room temperature and pressure, 0.29 dm³ of hydrogen is collected. Which of the following is the most likely volume of hydrogen produced if 0.2 g of sodium is used instead? (Assume same conditions and that both metals react completely. Relative atomic masses: Li=7, Na=23. 1 mol of gas occupies 24 dm³ at rtp.)
Hard
- A0.09 dm³
- B0.29 dm³
- C0.87 dm³
- D0.20 dm³
31.The table shows the melting points of three alkali metals. Which is the most likely melting point of rubidium?
Medium
- A39 °C
- B180 °C
- C97 °C
- D63 °C
32.A teacher demonstrates the reaction of sodium with water behind a safety screen. Which of the following best explains why the safety screen is used?
Easy
- ATo prevent the sodium from reacting with air
- BTo protect the audience from possible splashing of hot alkali
- CTo keep the water from evaporating
- DTo reduce the noise of the reaction
33.Which of the following is a word equation for the reaction of lithium with water?
Easy
- Alithium + water → lithium oxide + hydrogen
- Blithium + water → lithium hydroxide + hydrogen
- Clithium + water → lithium oxide + water
- Dlithium + water → lithium hydroxide + oxygen
34.A sample of an alkali metal is cut with a knife and a shiny surface is observed. After a few minutes, the surface becomes dull. Which property of alkali metals does this demonstrate?
Easy
- AThey have low melting points
- BThey are very reactive
- CThey are soft
- DThey have low densities
35.0.1 g of lithium is reacted with excess water. The hydrogen gas produced is collected at room temperature and pressure. Which of the following volumes of hydrogen is most likely to be collected? (Relative atomic mass: Li = 7; 1 mole of gas occupies 24 dm³ at rtp)
Medium
- A0.17 dm³
- B0.34 dm³
- C0.69 dm³
- D0.86 dm³
36.A student adds a small piece of potassium to water and observes a lilac flame. What is the most likely reason for the flame?
Medium
- AThe potassium burns in the air
- BThe hydrogen gas produced ignites
- CThe potassium hydroxide reacts with the water
- DThe water catches fire
37.Which of the following statements about alkali metals is true?
Easy
- AThey have high melting points
- BThey are stored in water
- CThey are very reactive
- DThey have high densities
38.Which of the following is the correct general word equation for the reaction of an alkali metal with water?
Easy
- Aalkali metal + water → metal oxide + hydrogen
- Balkali metal + water → metal hydroxide + hydrogen
- Calkali metal + water → metal oxide + water
- Dalkali metal + water → metal hydroxide + oxygen
39.The diagram shows the electron configuration of a sodium atom. Which group of the periodic table does sodium belong to?
Easy
- AGroup 2
- BGroup 1
- CGroup 7
- DGroup 0
40.What is the pH of the solution formed when an alkali metal reacts with water?
Easy
- ApH less than 7
- BpH equal to 7
- CpH greater than 7
- DpH exactly 7
41.The reactivity of the alkali metals goes up as you go up group 1.
Easy
True or false?
42.The melting points of the alkali metals go up as you go up group 1.
Easy
True or false?
43.The alkali metals react strongly with water.
Easy
True or false?
44.The alkali metals all have high melting points.
Easy
True or false?
45.Alkaline solutions have a pH greater than 7.
Easy
True or false?
46.Alkali metals are usually stored in oil.
Easy
True or false?
47.Match each alkali metal to the correct observation when a small piece is added to water.
Medium
- Lithium
- Potassium
- Caesium
- Fizzes, releasing hydrogen gas
- Hydrogen ignites with a lilac flame
- Very violent explosion
48.Arrange the following alkali metals in order of increasing reactivity (least reactive first).
Medium
- Lithium
- Potassium
- Sodium
- Rubidium
49.Which of the following are properties of alkali metals? Select all that apply.
Medium
- ALow melting points
- BHigh densities
- CSoft enough to be cut with a knife
- DVery reactive
- EStored in oil to prevent reaction with air and water
50.The melting points of alkali metals increase as you go down group 1.
Easy
True or false?
51.Complete the general word equation for the reaction between an alkali metal and water.
Easy
alkali metal + water → ____ + ____
52.Complete the word equation for the reaction between sodium and water.
Easy
sodium + water → ____ + ____
53.State an alkali metal which will have a stronger reaction with water than sodium.
Easy
54.Complete the word equation for the reaction between lithium and water.
Easy
lithium + water → ____ + ____
55.Complete the word equation for the reaction between rubidium and water.
Easy
rubidium + water → ____ + ____
56.State two safety precautions a teacher is likely to take when demonstrating the reaction between sodium and water.
Medium
57.Complete the word equation for the reaction of lithium with water.
Easy
lithium + water → ____ + ____
58.State two safety precautions a teacher should take when demonstrating the reaction of sodium with water.
Medium
59.A 0.1 g piece of lithium (relative atomic mass 7) is added to excess water. Calculate the volume of hydrogen gas produced at room temperature and pressure (24 dm³/mol). Give your answer in dm³.
Hard
60.A 0.1 g piece of lithium (relative atomic mass 7) is added to excess water. Calculate the volume of hydrogen gas produced at room temperature and pressure (24 dm³/mol). Give your answer in dm³.
Hard
- A2.171 dm³
- B0.171 dm³
- C-0.829 dm³
- D1.171 dm³

复习笔记

## Alkali Metals (Group 1) - **Properties**: Soft (cut with knife), low melting points, low densities, very reactive. - **Storage**: Stored in oil to keep away air and water. - **Reactivity trend**: Increases down the group; melting points decrease down the group. - **Reaction with water**: Forms metal hydroxide + hydrogen. - General equation: **alkali metal + water → metal hydroxide + hydrogen** - Lithium: fizzes, releases hydrogen. - Potassium: more reactive, hydrogen ignites. - Caesium: even stronger reaction. - **Alkaline solutions**: pH > 7. - **Safety**: Reactions are dangerous; use safety screen, small amounts.

Alkali metals: The elements in group 1 of the periodic table; they are soft, have low melting points, low densities, and are very reactive.
Metal hydroxide: The product formed when an alkali metal reacts with water; it is alkaline (pH > 7).
Hydrogen: A gas released when alkali metals react with water; can ignite with more reactive metals.

闪卡

What is the first group of the periodic table called?

Alkali metals.

What are three common properties of alkali metals?

Low melting points, softness (can be cut with a knife), and low densities.

Why are alkali metals stored in oil?

To keep air and water away from them because they are very reactive.

How does reactivity change as you go down Group 1?

Reactivity increases as you go down Group 1.

How do melting points change as you go down Group 1?

Melting points decrease as you go down Group 1.

What is the general word equation for the reaction of an alkali metal with water?

alkali metal + water → metal hydroxide + hydrogen

What is the word equation for lithium reacting with water?

lithium + water → lithium hydroxide + hydrogen

What is the word equation for potassium reacting with water?

potassium + water → potassium hydroxide + hydrogen

What is the word equation for caesium reacting with water?

caesium + water → caesium hydroxide + hydrogen

What is observed when lithium is added to water?

It fizzes due to the release of hydrogen gas.

Why does potassium react more strongly with water than lithium?

Potassium is more reactive than lithium, so the reaction is stronger and the hydrogen gas ignites.

What pH do alkaline solutions have?

pH greater than 7.

True or false: The reactivity of alkali metals increases as you go up Group 1.

False. Reactivity increases as you go down Group 1.

True or false: The melting points of alkali metals increase as you go up Group 1.

True. Melting points decrease as you go down, so they increase as you go up.

True or false: Alkali metals react strongly with water.

True.

True or false: Alkali metals have high melting points.

False. They have low melting points.

True or false: Alkaline solutions have a pH greater than 7.

True.

True or false: Alkali metals are usually stored in oil.

True.

Complete the word equation: sodium + water → ?

sodium + water → sodium hydroxide + hydrogen

Name an alkali metal that reacts more strongly with water than sodium.

Potassium (or rubidium, caesium, etc.)

Complete the word equation: rubidium + water → ?

rubidium + water → rubidium hydroxide + hydrogen

What safety precautions should be taken when demonstrating alkali metal reactions with water?

Use a safety screen and only small amounts of the alkali metal.

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