How many moles are in 36.0g. of H2O?

2.0 moles

Explanation:

The relationship between the number of moles of a given substance present in a sample and the mass of the sample is given by the molar mass of the substance.

For any chemical species, you have

molar mass

=

the mass of exactly 1 mole

water has a molar mass of

18.015 g mol

−

1

which means that

1

mole of water has a mass of

18.015 g

.

18.015 g mol

−

1

=

18.015 g

1 mole H

2

O

So for every

18.015 g

of water present in your sample, you have

1

mole of water.

This means that your

36-g

sample will contain

36

g

⋅

given by the molar mass of H

2

O



1 mole H

2

O

18.015

g

=

2.0 moles H

2

O

~~~

The answer must be rounded to two sig figs, the number of sig figs you have for the mass of water.

Explanation:

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol

the electron configuration that you gave me has 16 electrons ergo it has 16 protons ergo it is the element sulfur.