How many water molecules in a $0.90 \cdot g$ $0.90*g$ mass of water?

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How many water molecules in a $0.90 \cdot g$ $0.90*g$ mass of water?

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Answer 1 · 2017-10-25T16:56:28

$3.01 \times 10^{22}$ $3.01xx10^22$ molecules.

Explanation:

The mass of one mole of water is $18 g$ $"18 g"$ . Therefore, $0.9 g$ $"0.9 g"$ of water is

$\frac{0.9 g}{18 g/mol} = 0.05 moles$ $"0.9 g"/"18 g/mol" = "0.05 moles"$

of water. One mole of water contains Avagadro's constant, ie, $6.022 \times 10^{23}$ $6.022 xx 10^23$ molecules of water, therefore, $0.05$ $0.05$ moles of water contain

$0.05 mol \times \frac{{6.022}^{23} molec.}{1 mol} = 3.01 \times 10^{22}$ $"0.05 mol" xx (6.022^23"molec.")/("1 mol") = 3.01xx10^22$ $molecules$ $"molecules"$

Answer 2 · 2017-10-25T16:58:41

We find the molar quantity.....and get $number of water molecules$ $"number of water molecules"$ $= 3.01 \times 10^{22}$ $=3.01xx10^22$ ...

Explanation:

$Moles of water = \frac{0.9 \cdot g}{18.01 \cdot g \cdot m o l^{- 1}} = 0.050 \cdot m o l$ $"Moles of water"=(0.9*g)/(18.01*g*mol^-1)=0.050*mol$

And we know that there are $6.022 \times 10^{23}$ $6.022xx10^23$ molecules in one mole of any substance.....

And so we take the product......

$0.050 \cdot m o l \times 6.022 \times 10^{23} \cdot m o l^{- 1} = 3.01 \times 10^{22}$ $0.050*molxx6.022xx10^23*mol^-1=3.01xx10^22$ $water molecules$ $"water molecules"$ . (And thus the product gives a dimensionless number as required....)

(i) how many oxygen atoms in this molar quantity; and (ii) how many hydrogen atoms......?

Answer 3 · 2017-10-25T17:08:06

$30.1$ $30.1$ x $10^{21} m l c s$ $10^21 mlcs$

Explanation:

$M a s s o f w a t e r (H_{2} O)$ $Mass of water(H_2O)$ $= 0.9 g r a m s$ $= 0.9grams$

$M o l a r m a s s o f (H_{2} O)$ $Molar mass of (H_2O)$ $= 1.008$ $= 1.008$ x $2$ $2$ + 1 $6$ $6$
$= 18.016 g m o l^{-}$ $= 18.016gmol^-$

** Number of molecules ** = Mass in grams $/$ $/$ Molar mass x $N_{A}$ $N_A$

$= \frac{0.9}{18.016}$ $= 0.9/18.016$ x $6.02$ $6.02$ x $10^{23}$ $10^23$

$= 30.1$ $= 30.1$ x $10^{21}$ $10^21$ $m l c s$ $mlcs$

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How many water molecules in a $0.90 \cdot g$ $0.90*g$ mass of water?

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