Pls i have a chemistry test answers asap :'(

How many sig figs does 0.00002 have?

DiKsa [7]

5 sig figs! count everything after the decimal

8 0

3 years ago

Find the mass in grams of 1.55 x 1023 molecules of Cl2?

forsale [732]

We are told that there are 1.55 x 10²³ molecules of Cl₂ and we need to calculate the mass of these molecules. We need to do several conversions. The easiest will be to convert the amount of molecules to the number of moles present. To do this, we need to use Avogadro's number which is 6.022 x 10²³ molecules/mole.

1.55 x 10²³ molecules / 6.022 x 10²³ molecules/mole = 0.257 moles Cl₂

Now that we have the moles of Cl₂ present, we can convert this value to a mass of Cl₂ by using the molecular mass of Cl₂. The molecular mass is 70.906 g/mol.

0.257 moles Cl₂ x 70.906 g/mol = 18.3 g Cl₂

Therefore, 1.55 x 10²³ molecules of Cl₂ will have a mass of 18.3 g.

7 0

3 years ago

Calculate the number of hydrogen atoms present in 40g of urea, (NH2)2CO

tekilochka [14]

Answer: There are $16.14 \times 10^{23}$ atoms of hydrogen are present in 40g of urea, $(NH_{2})_{2}CO$ .

Explanation:

Given: Mass of urea = 40 g

Number of moles is the mass of substance divided by its molar mass.

First, moles of urea (molar mass = 60 g/mol) are calculated as follows.

$Moles = \frac{mass}{molar mass}\\= \frac{40 g}{60 g/mol}\\= 0.67 mol$

According to the mole concept, 1 mole of every substance contains $6.022 \times 10^{23}$ atoms.

So, the number of atoms present in 0.67 moles are as follows.

$0.67 mol \times 6.022 \times 10^{23} atoms/mol\\= 4.035 \times 10^{23} atoms$

In a molecule of urea there are 4 hydrogen atoms. Hence, number of hydrogen atoms present in 40 g of urea is as follows.

$4 \times 4.035 \times 10^{23} atoms\\= 16.14 \times 10^{23} atoms$

Thus, we can conclude that there are $16.14 \times 10^{23}$ atoms of hydrogen are present in 40g of urea, $(NH_{2})_{2}CO$ .

7 0

2 years ago

Define reaction rate

suter [353]

Answer:

The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. Reaction rates can vary dramatically.

4 0

3 years ago

5. A gas at 127०C and 10.0 L expands to 20.0 L. What is the new temperature in Celcius? (HINT: You need to convert to Kelvins so

antoniya [11.8K]

Answer:

The new temperature is 527.15 ºC.

Explanation:

Charles’s law states that the volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature of the gas (the absolute temperature is the Kelvin temperature).

We need to calculate the temperature after the expansion, that is T₂. For that, we use Charles' law:

$V₁ ÷ T₁ = V₂ ÷ T₂$

Because we have to use the absolute temperature, we convert ºC to K adding 273.15:

T₁ = 127 ºC + 273.15 ºC = 400.15 K

$T₂ = V₂ × T₁ ÷ V₁$

$T₂ = 20. 0 L × 400.15 K ÷ 10.0 L$

T₂ = 800.3 K

We substract 273.15 to the result to convert it back to ºC:

T₂ = 800.3 - 273.15 = 527.15 ºC.

4 0

3 years ago

Pls i have a chemistry test answers asap :'(​

Pls i have a chemistry test answers asap :'(