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2 years ago

How many moles are in 25 grams of Li? How do you know?

Chemistry

1 answer:

Ipatiy [6.2K]2 years ago

8 0

Answer:

3.6mol Li

Explanation:

To get the amount of moles from the mass we divide the mass by the molar mass.

25g ÷ 6.941g/mol = 3.6mol Li

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What is the de broglie wavelength of a 0.17-kg hockey puck moving at 37 m/s ?

Stolb23 [73]

Im taking lambda as x (wavelength)

m = 0.17 kg

v=37m/s

h=6.62*10^-34m²kg/s

x= h/mv

$x = 6.62 \times 10 ^{ - 34} \div 0.17 \times 37$
$x =1.05 \times {10}^{ - 34} m$

5 0

2 years ago

Identify the following example as a physical or chemical change. Moisture in the air forms beads of water on a cold window pane.

denis23 [38]

Answer: The given example is a physical change.

Explanation:

A chemical change is defined as the change in which chemical composition of a substance changes and results in the formation of a new substance. These are usually irreversible process.

A physical change is defined as the change in which only the shape and size of the substance changes and no new substance is formed. Only phase change occurs in these processes. These are usually considered as a reversible change.

For the given example: Moisture in the air forms beads of water on a cold window pane.

This is a physical change because water was initially present in the gaseous state (Moisture in the air) and when it is coming in contact with the cold window pane, the gaseous state of water gets converted into a liquid state.

Hence, the given example is a physical change.

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2 years ago

A sample of a gas at 25°C has a volume of 150 mL when its pressure is 0.947 atm. What will the temperature of the gas be at a pr

dezoksy [38]

Answer:

25°C

Explanation:

Combined Gas Law (P₁V₁)/T₁ = (P₂V₂)/T₂

(0.947 atm)(150 mL)/25°C = (0.987 atm)(144mL)/T₂

5.682 = 142.128/T₂

T₂ = 142.128/5.682

T₂ = 25.0137272756°C = 25°C

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2 years ago

Sodium chloride procedure

MAVERICK [17]

Answer: Dissolve approximately 3 mg of Sodium Chloride in 2 mL of water.

Add 0.4 mL of silver nitrate TS and acidify with diluted nitric acid.

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2 years ago

How many moles of oxygen atoms are present in 30.5 grams of hydrogen peroxide (h2o2)?

Pepsi [2]

1.8 moles of oxygen atoms are present in 30.5 grams of hydrogen peroxide.

Explanation:

First we have to convert the given weight of hydrogen peroxide to molar mass of hydrogen peroxide. So for this, we have to divide the given weight with the molecular mass of hydrogen peroxide.

$\text {Molecular mass of } \mathrm{H}_{2} \mathrm{O}_{2}=(2 \times 1)+(2 \times 16)=2+32=34 \mathrm{g}$

So,

$\text {Molar mass of } \mathrm{H}_{2} \mathrm{O}_{2}=\frac{30.5}{34}=0.90 \text { moles of } \mathrm{H}_{2} \mathrm{O}_{2}$

Second step, in this moles, 2 molecules of oxygen are present. Thus 1 mole of Hydrogen peroxide consists of 2 moles of oxygen. Then,

$0.90 moles of $\mathrm{H}_{2} \mathrm{O}_{2}=2 \times 0.90=1.8$ moles of oxygen$

So, 30.5 grams of hydrogen peroxide consists of 1.8 moles of oxygen.

4 0

2 years ago