#whatsapp_btn{
    display:block;
    position:fixed;
    bottom:40px;
    right:0;
    z-index:99999999;
    width: 50px;
    height: 50px;
    overflow: hidden;
    transition: .3s;
}

#whatsapp_btn:hover{
    width: 110px;
}



#whatsapp_btn img{
    height: 100%;
    position:absolute;
    left:0
}

@media screen and (min-width:768px){
    #whatsapp_btn{
        bottom:70px;
        right:0;
        width:70px;
        height:70px;
    }
}