Question

Which substance has a molar mass of 33.99 g/mol?

Answer 1

Answer:

PH₃.

Explanation:

Hello.

In this case, among the options:

PH₃, GaF₃, SF₂ and CO₂

We compute their molar masses by adding the atomic masses of the constituting elements by their subscripts:

$M_{PH_3}=m_P+3*m_H=30.97+3*1.01=34.00g/mol\\\\M_{GaF_3}=m_{Ga}+3*m_F=69.72+3*19.00=126.72g/mol\\\\M_{SF_2}=m_{S}+2*m_F=32.07+2*19.00=70.07g/mol\\\\M_{CO_2}=m_{C}+2*m_O=12.01+2*16.00=44.01g/mol$

Thus, the answer is PH₃.

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